MBS (Details 2) (USD $)	3 Months Ended									3 Months Ended
	Mar. 31, 2013 Security	Mar. 31, 2012	Mar. 31, 2012 Low end of range	Mar. 31, 2013 Agency MBS Security	Mar. 31, 2012 Agency MBS	Mar. 31, 2013 Agency MBS Fannie Mae. Security	Dec. 31, 2012 Agency MBS Fannie Mae.	Mar. 31, 2013 Agency MBS Freddie Mac. Security	Dec. 31, 2012 Agency MBS Freddie Mac.	Mar. 31, 2013 Non-Agency MBS Security	Mar. 31, 2012 Non-Agency MBS	Mar. 31, 2012 Non-Agency MBS Weighted average	Mar. 31, 2012 Non-Agency MBS Low end of range	Mar. 31, 2012 Non-Agency MBS High end of range	Mar. 31, 2013 Non-Agency MBS Discount Designated as Credit Reserve and OTTI	Mar. 31, 2012 Non-Agency MBS Discount Designated as Credit Reserve and OTTI	Mar. 31, 2013 Non-Agency MBS Accretable Discount	Mar. 31, 2012 Non-Agency MBS Accretable Discount	Mar. 31, 2013 Non-Agency MBS Rated A Security	Dec. 31, 2012 Non-Agency MBS Rated A	Mar. 31, 2013 Non-Agency MBS Rated BBB Security	Dec. 31, 2012 Non-Agency MBS Rated BBB	Mar. 31, 2013 Non-Agency MBS Rated BB Security	Dec. 31, 2012 Non-Agency MBS Rated BB	Mar. 31, 2013 Non-Agency MBS Rated CCC Security	Dec. 31, 2012 Non-Agency MBS Rated CCC	Mar. 31, 2013 Non-Agency MBS Rated C Security	Dec. 31, 2012 Non-Agency MBS Rated C	Mar. 31, 2013 Non-Agency MBS Unrated and other Security	Dec. 31, 2012 Non-Agency MBS Unrated and other
Fair Value
Less than 12 months	$ 1,095,547,000			$ 1,076,488,000		$ 550,988,000		$ 525,500,000		$ 19,059,000																	$ 3,869,000		$ 15,190,000
12 months or more	109,170,000			45,580,000		42,957,000		2,623,000		63,590,000									989,000		20,225,000		2,130,000		23,683,000				16,563,000
Total	1,204,717,000			1,122,068,000		593,945,000		528,123,000		82,649,000									989,000		20,225,000		2,130,000		23,683,000		3,869,000		31,753,000
Unrealized Losses
Less than 12 months	5,188,000			5,078,000		2,063,000		3,015,000		110,000																	22,000		88,000
12 months or more	3,292,000			779,000		777,000		2,000		2,513,000									41,000		691,000		233,000		1,476,000				72,000
Total	8,480,000			5,857,000		2,840,000		3,017,000		2,623,000									41,000		691,000		233,000		1,476,000		22,000		160,000
Number of Securities
Less than 12 months (in security)	132			129		66		63		3																	2		1
12 months or more (in security)	25			12		11		1		13									2		2		3		4				2
OTTI charges recorded
Total OTTI losses		(879,000)
OTTI reclassified from OCI		(41,000)
OTTI recognized in earnings		(920,000)									(920,000)
Roll-forward of the credit loss component of OTTI
Credit loss component of OTTI at beginning of period	36,115,000	34,915,000
Additions for credit related OTTI not previously recognized		458,000
Subsequent additional credit related OTTI recorded		462,000
Credit loss component of OTTI at end of period	36,115,000	35,835,000
Significant inputs considered and assumptions made in determining the measurement of the component of OTTI recorded in earnings
Credit enhancement (as a percent)												4.40%	0.00%	16.50%
Projected CPR (as a percent)												10.20%	9.40%	13.30%
Projected Loss Severity (as a percent)												55.40%	45.90%	60.00%
60+ days delinquent (as a percent)												21.50%	18.20%	23.80%
Number of days considered to classify loans delinquent			60 days
Changes in the components of the purchase discount on Non-Agency MBS
Balance at beginning of period															(1,380,506,000)	(1,228,766,000)	(371,626,000)	(250,479,000)
Accretion of discount																	12,051,000	9,410,000
Realized credit losses															50,307,000	22,394,000
Purchases															(23,535,000)	(108,449,000)	11,229,000	(7,433,000)
Sales															6,283,000		932,000
Reclassification adjustment for OTTI																684,000		(684,000)
Net impairment losses recognized in earnings																(920,000)
Unlinking of Linked Transactions																(38,579,000)		(6,078,000)
Transfers/release of credit reserve															34,499,000	8,918,000	(34,499,000)	(8,918,000)
Balance at end of period															(1,312,952,000)	(1,344,718,000)	(381,913,000)	(264,182,000)
Purchase discount pertaining to linked transactions designated as accretable purchase discount reallocated to credit reserve											629,000
Purchase discount pertaining to linked transactions designated as credit reserve reallocated to accretable purchase discount										13,000
AOCI from MBS:
Balance at the beginning of the period	824,808,000	55,491,000		200,943,000		154,950,000	177,605,000	18,210,000	22,836,000	623,865,000									(41,000)	(85,000)	1,388,000	744,000	7,855,000	4,580,000	162,457,000	128,849,000	80,546,000	81,362,000	413,765,000	324,677,000
Unrealized loss on Agency MBS, net	(27,291,000)	(3,158,000)
Unrealized gain on Non-Agency MBS, net	146,730,000	262,602,000
Reclassification adjustment for MBS sales included in net income	(1,360,000)	(2,901,000)
Reclassification adjustment for OTTI included in net income		920,000
Change in AOCI from MBS	118,079,000	257,463,000
Balance at the end of period	942,887,000	312,954,000		173,652,000		154,950,000	177,605,000	18,210,000	22,836,000	769,235,000									(41,000)	(85,000)	1,388,000	744,000	7,855,000	4,580,000	162,457,000	128,849,000	80,546,000	81,362,000	413,765,000	324,677,000
Sales of MBS
Amount of MBS sold					71,100,000					6,100,000
Gross gains on sale of MBS	1,633,000	2,953,000			3,000,000					1,700,000
MBS Interest Income
Coupon interest				57,504,000	64,008,000					67,933,000	60,860,000
Effective yield adjustment				(14,717,000)	(10,708,000)					11,982,000	9,344,000
Interest on mortgage backed securities				$ 42,787,000	$ 53,300,000					$ 79,915,000	$ 70,204,000