Fair Value Measurements Schedule of Financial Assets, Fair Value Hierarchy (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value Measured on Recurring Basis
Available-for-sale securities	$ 219,931	$ 203,290
U.S. Treasury securities
Fair Value Measured on Recurring Basis
Available-for-sale securities	61,184	17,363
U.S. Treasury securities \| Fair value measured on a recurring basis \| Level 1
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
U.S. Treasury securities \| Fair value measured on a recurring basis \| Level 2
Fair Value Measured on Recurring Basis
Available-for-sale securities	61,184	17,363
U.S. Treasury securities \| Fair value measured on a recurring basis \| Level 3
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
GSE securities
Fair Value Measured on Recurring Basis
Available-for-sale securities	23,554	46,468
GSE securities \| Fair value measured on a recurring basis \| Level 1
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
GSE securities \| Fair value measured on a recurring basis \| Level 2
Fair Value Measured on Recurring Basis
Available-for-sale securities	23,554	46,468
GSE securities \| Fair value measured on a recurring basis \| Level 3
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
Collateralized mortgage obligations
Fair Value Measured on Recurring Basis
Available-for-sale securities	63,669	67,066
Collateralized mortgage obligations \| Fair value measured on a recurring basis \| Level 1
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
Collateralized mortgage obligations \| Fair value measured on a recurring basis \| Level 2
Fair Value Measured on Recurring Basis
Available-for-sale securities	63,669	67,066
Collateralized mortgage obligations \| Fair value measured on a recurring basis \| Level 3
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
Commercial mortgage-backed securities
Fair Value Measured on Recurring Basis
Available-for-sale securities	49,369	46,429
Commercial mortgage-backed securities \| Fair value measured on a recurring basis \| Level 1
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
Commercial mortgage-backed securities \| Fair value measured on a recurring basis \| Level 2
Fair Value Measured on Recurring Basis
Available-for-sale securities	49,369	46,429
Commercial mortgage-backed securities \| Fair value measured on a recurring basis \| Level 3
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
GSE residential mortgage-backed securities
Fair Value Measured on Recurring Basis
Available-for-sale securities	2,178	2,368
GSE residential mortgage-backed securities \| Fair value measured on a recurring basis \| Level 1
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
GSE residential mortgage-backed securities \| Fair value measured on a recurring basis \| Level 2
Fair Value Measured on Recurring Basis
Available-for-sale securities	2,178	2,368
GSE residential mortgage-backed securities \| Fair value measured on a recurring basis \| Level 3
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
Asset backed securities
Fair Value Measured on Recurring Basis
Available-for-sale securities	3,750	4,053
Asset backed securities \| Fair value measured on a recurring basis \| Level 1
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
Asset backed securities \| Fair value measured on a recurring basis \| Level 2
Fair Value Measured on Recurring Basis
Available-for-sale securities	3,750	4,053
Asset backed securities \| Fair value measured on a recurring basis \| Level 3
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
Pooled trust preferred securities
Fair Value Measured on Recurring Basis
Available-for-sale securities	16,227	19,542
Pooled trust preferred securities \| Fair value measured on a recurring basis \| Level 1
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
Pooled trust preferred securities \| Fair value measured on a recurring basis \| Level 2
Fair Value Measured on Recurring Basis
Available-for-sale securities	0	0
Pooled trust preferred securities \| Fair value measured on a recurring basis \| Level 3
Fair Value Measured on Recurring Basis
Available-for-sale securities	16,227	19,542
GSE preferred stock
Fair Value Measured on Recurring Basis
Available-for-sale securities		1
GSE preferred stock \| Fair value measured on a recurring basis \| Level 1
Fair Value Measured on Recurring Basis
Available-for-sale securities		1
GSE preferred stock \| Fair value measured on a recurring basis \| Level 2
Fair Value Measured on Recurring Basis
Available-for-sale securities		0
GSE preferred stock \| Fair value measured on a recurring basis \| Level 3
Fair Value Measured on Recurring Basis
Available-for-sale securities		$ 0

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

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+ Details

CFS BANCORP INC 10-Q