Investments (Private Label Mortgage Backed Securities) (Details) (USD $) In Thousands, unless otherwise specified			9 Months Ended
Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 RALI2004-QS4 A7 [Member]	Sep. 30, 2012 MALT2004-6 7A1 [Member]	Sep. 30, 2012 RALI2005-QS2 A1 [Member]	Sep. 30, 2012 RALI2006-QS4 A2 [Member]	Sep. 30, 2012 GSR 2006-5F 2A1 [Member]	Sep. 30, 2012 RALI2006-QS8 A1 [Member]	Sep. 30, 2012 Private-label mortgage-backed securities [Member]	Dec. 31, 2011 Private-label mortgage-backed securities [Member]
Schedule of Investments [Line Items]
Origination Date			Mar. 01, 2004	Jun. 01, 2004	Feb. 01, 2005	Apr. 01, 2006	May 01, 2006	Jul. 28, 2006
Amortized Cost	$ 131,830	$ 123,874	$ 358	$ 559	$ 475	$ 752	$ 168	$ 398	$ 2,710	$ 3,366
Fair Value	134,321	125,301	356	536	475	638	154	350	2,509	2,867
Gross Unrealized Gain (Loss)			(2)	(23)		(114)	(14)	(48)	(201)	(500)
Collateral Type			ALT A	ALT A	ALT A	ALT A	Prime	ALT A
Lowest Credit Rating Assigned			AA	B	CC	D	C	D
Credit Support %			12.31%	11.92%	7.06%		0.79%
Cumulative OTTI Charges	$ 440	$ 390				$ 253		$ 187	$ 440

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

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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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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

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Reference 9: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity).

+ References+ Details