v3.25.3

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2025	Oct. 27, 2025
Cover [Abstract]
Document Type	10-Q
Document Period End Date	Sep. 30, 2025
Document Transition Report	false
Entity File Number	1-13998
Entity Registrant Name	Insperity, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	76-0479645
Entity Address, Address Line One	19001 Crescent Springs Drive
Entity Address, City or Town	Kingwood,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77339
City Area Code	281
Local Phone Number	358-8986
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Common Stock, Shares Outstanding		37,704,152
Entity Central Index Key	0001000753
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Information [Line Items]
Entity Registrant Name	Insperity, Inc.
Entity Shell Company	false
Entity Emerging Growth Company	false
Document Quarterly Report	true
Common Stock [Member]
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol	NSP
Security Exchange Name	NYSE

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Indicate number of shares or other units outstanding of each of registrant's classes of capital or common stock or other ownership interests, if and as stated on cover of related periodic report. Where multiple classes or units exist define each class/interest by adding class of stock items such as Common Class A [Member], Common Class B [Member] or Partnership Interest [Member] onto the Instrument [Domain] of the Entity Listings, Instrument.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Boolean flag that is true when the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Indicates that the company is a Smaller Reporting Company (SRC).

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Local phone number for entity.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Name of the Exchange on which a security is registered.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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INSPERITY, INC. 10-Q