Investments - Below investment grade securities (Details) (USD $) In Thousands, unless otherwise specified						6 Months Ended
Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Private label residential mortgage backed securities	Dec. 31, 2011 Private label residential mortgage backed securities	Jun. 30, 2012 Below investment grade Private label residential mortgage backed securities	Jun. 30, 2012 PHHAM Below investment grade Private label residential mortgage backed securities	Jun. 30, 2012 CWALT ONE Below investment grade Private label residential mortgage backed securities	Jun. 30, 2012 CWALT TWO Below investment grade Private label residential mortgage backed securities	Jun. 30, 2012 FHAMS Below investment grade Private label residential mortgage backed securities	Jun. 30, 2012 BAALT Below investment grade Private label residential mortgage backed securities	Jun. 30, 2012 ABFS Below investment grade Private label residential mortgage backed securities	Jun. 30, 2012 CONHE Below investment grade Private label residential mortgage backed securities
Schedule of Available-for-sale Securities
Debt Securities, Amortized Cost			$ 7,250	$ 8,408	$ 5,586	$ 2,180	$ 716	$ 331	$ 1,919	$ 111	$ 281	$ 48
Available-for-sale Securities	322,931	328,413			4,821	1,794	613	249	1,799	64	231	71
Unrealized Gain (Loss)	$ 10,756	$ 7,008	$ 581		$ (765)	$ (386)	$ (103)	$ (82)	$ (120)	$ (47)	$ (50)	$ 23
12 Month Historical Prepayment Rates %						10.82%	12.01%	11.10%	11.71%	9.68%	10.70%	9.89%
Projected Default Rates %						22.80%	27.50%	30.40%	19.10%	11.90%	11.47%	6.35%
Projected Severity Rates %						51.00%	59.20%	56.30%	63.90%	44.50%	65.25%	100.00%
Original Purchase Price %						97.25%	100.73%	101.38%	95.00%	97.24%	97.46%	86.39%
Current Credit Enhancement %						0.00%	4.86%	(0.45%)	(0.24%)	3.70%	0.00%	0.00%

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

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