Name:	cmo_DocumentAndEntityInformationLineItems
Namespace Prefix:	cmo_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.

No definition available.

Name:	dei_AmendmentFlag
Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

Area code of city

No definition available.

Name:	dei_CityAreaCode
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is YYYY-MM-DD.

No definition available.

Name:	dei_DocumentPeriodEndDate
Namespace Prefix:	dei_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.

No definition available.

Name:	dei_DocumentType
Namespace Prefix:	dei_
Data Type:	dei:submissionTypeItemType
Balance Type:	na
Period Type:	duration

Address Line 1 such as Attn, Building Name, Street Name

No definition available.

Name:	dei_EntityAddressAddressLine1
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

Address Line 2 such as Street or Suite number

No definition available.

Name:	dei_EntityAddressAddressLine2
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

Address Line 3 such as an Office Park

No definition available.

Name:	dei_EntityAddressAddressLine3
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

Name of the City or Town

No definition available.

Name:	dei_EntityAddressCityOrTown
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

Code for the postal or zip code

No definition available.

Name:	dei_EntityAddressPostalZipCode
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

Name of the state or province.

No definition available.

Name:	dei_EntityAddressStateOrProvince
Namespace Prefix:	dei_
Data Type:	dei:stateOrProvinceItemType
Balance Type:	na
Period Type:	duration

A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation 12B
-Number 240
-Section 12
-Subsection b-2

Name:	dei_EntityCentralIndexKey
Namespace Prefix:	dei_
Data Type:	dei:centralIndexKeyItemType
Balance Type:	na
Period Type:	duration

Indicate if registrant meets the emerging growth company criteria.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation 12B
-Number 240
-Section 12
-Subsection b-2

Name:	dei_EntityEmergingGrowthCompany
Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.

No definition available.

Name:	dei_EntityFileNumber
Namespace Prefix:	dei_
Data Type:	dei:fileNumberItemType
Balance Type:	na
Period Type:	duration

Two-character EDGAR code representing the state or country of incorporation.

No definition available.

Name:	dei_EntityIncorporationStateCountryCode
Namespace Prefix:	dei_
Data Type:	dei:edgarStateCountryItemType
Balance Type:	na
Period Type:	duration

The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation 12B
-Number 240
-Section 12
-Subsection b-2

Name:	dei_EntityRegistrantName
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation 12B
-Number 240
-Section 12
-Subsection b-2

Name:	dei_EntityTaxIdentificationNumber
Namespace Prefix:	dei_
Data Type:	dei:employerIdItemType
Balance Type:	na
Period Type:	duration

Local phone number for entity.

No definition available.

Name:	dei_LocalPhoneNumber
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 13e
-Subsection 4c

Name:	dei_PreCommencementIssuerTenderOffer
Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 14d
-Subsection 2b

Name:	dei_PreCommencementTenderOffer
Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

Title of a 12(b) registered security.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b

Name:	dei_Security12bTitle
Namespace Prefix:	dei_
Data Type:	dei:securityTitleItemType
Balance Type:	na
Period Type:	duration

Name of the Exchange on which a security is registered.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection d1-1

Name:	dei_SecurityExchangeName
Namespace Prefix:	dei_
Data Type:	dei:edgarExchangeCodeItemType
Balance Type:	na
Period Type:	duration

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as soliciting material pursuant to Rule 14a-12 under the Exchange Act.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Section 14a
-Number 240
-Subsection 12

Name:	dei_SolicitingMaterial
Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

Trading symbol of an instrument as listed on an exchange.

No definition available.

Name:	dei_TradingSymbol
Namespace Prefix:	dei_
Data Type:	dei:tradingSymbolItemType
Balance Type:	na
Period Type:	duration

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as written communications pursuant to Rule 425 under the Securities Act.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Securities Act
-Number 230
-Section 425

CAPSTEAD MORTGAGE CORP 8-K