MBS (Details 2) (USD $)	3 Months Ended													3 Months Ended
	Mar. 31, 2012 Security	Mar. 31, 2011	Mar. 31, 2012 Discount Designated as Credit Reserve and OTTI	Mar. 31, 2011 Discount Designated as Credit Reserve and OTTI	Mar. 31, 2012 Accretable Discount	Mar. 31, 2011 Accretable Discount	Mar. 31, 2012 Low end of range D	Mar. 31, 2012 Agency MBS Security	Mar. 31, 2011 Agency MBS	Mar. 31, 2012 Agency MBS Fannie Mae. Security	Dec. 31, 2011 Agency MBS Fannie Mae.	Mar. 31, 2012 Agency MBS Freddie Mac. Security	Dec. 31, 2011 Agency MBS Freddie Mac.	Mar. 31, 2012 Non-Agency MBS Security	Mar. 31, 2011 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, 2012 Non-Agency MBS Rated AAA Security	Dec. 31, 2011 Non-Agency MBS Rated AAA	Mar. 31, 2012 Non-Agency MBS Rated AA Security	Dec. 31, 2011 Non-Agency MBS Rated AA	Mar. 31, 2012 Non-Agency MBS Rated A Security	Dec. 31, 2011 Non-Agency MBS Rated A	Mar. 31, 2012 Non-Agency MBS Rated BBB Security	Dec. 31, 2011 Non-Agency MBS Rated BBB	Mar. 31, 2012 Non-Agency MBS Rated BB Security	Dec. 31, 2011 Non-Agency MBS Rated BB	Mar. 31, 2012 Non-Agency MBS Rated B Security	Dec. 31, 2011 Non-Agency MBS Rated B	Mar. 31, 2012 Non-Agency MBS Rated CCC Security	Dec. 31, 2011 Non-Agency MBS Rated CCC	Mar. 31, 2012 Non-Agency MBS Rated CC Security	Dec. 31, 2011 Non-Agency MBS Rated CC	Mar. 31, 2012 Non-Agency MBS Rated C Security	Dec. 31, 2011 Non-Agency MBS Rated C	Mar. 31, 2012 Non-Agency MBS Unrated and other Security	Dec. 31, 2011 Non-Agency MBS Unrated and other
Fair Value
Less than 12 months	$ 1,805,529,000							$ 455,666,000		$ 435,903,000		$ 19,763,000		$ 1,349,863,000					$ 11,207,000						$ 21,592,000		$ 58,148,000		$ 106,974,000		$ 272,813,000		$ 175,181,000		$ 339,136,000		$ 364,812,000
12 months or more	1,099,770,000							52,784,000		49,880,000		2,904,000		1,046,986,000							34,000		23,239,000		18,468,000		14,233,000		82,603,000		77,767,000		180,793,000		445,331,000		204,518,000
Total	2,905,299,000							508,450,000		485,783,000		22,667,000		2,396,849,000					11,207,000		34,000		23,239,000		40,060,000		72,381,000		189,577,000		350,580,000		355,974,000		784,467,000		569,330,000
Unrealized Losses
Less than 12 months	51,477,000							978,000		927,000		51,000		50,499,000					111,000						1,037,000		2,438,000		4,818,000		9,000,000		7,658,000		8,738,000		16,699,000
12 months or more	64,908,000							544,000		534,000		10,000		64,364,000							14,000		3,273,000		1,417,000		970,000		6,071,000		8,270,000		9,937,000		21,288,000		13,124,000
Total	116,385,000							1,522,000		1,461,000		61,000		114,863,000					111,000		14,000		3,273,000		2,454,000		3,408,000		10,889,000		17,270,000		17,595,000		30,026,000		29,823,000
Number of Securities
Less than 12 months	157							33		31		2		124					1						4		6		7		25		15		31		35
12 months or more	85							11		10		1		74							1		3		4		3		8		8		11		22		14
Number of securities held with recognized credit-related OTTI losses														5
Credit-related OTTI losses recognized during the period	920,000													920,000
OTTI charges recorded
Total OTTI losses	879,000
OTTI reclassified from other comprehensive income	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	34,915,000	24,345,000
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	35,835,000	24,345,000
Significant inputs considered and assumptions made in determining the measurement of the component of OTTI recorded in earnings
Credit enhancement																4.40%	0.00%	16.50%
Projected CPR																10.20%	9.40%	13.30%
Projected Loss Severity																55.40%	45.90%	60.00%
60+ days delinquent																21.50%	18.20%	23.80%
Number of days considered to classify loans delinquent							60
Accumulated other comprehensive income from MBS:
Balance at the beginning of the period	55,491,000	393,822,000						216,256,000		185,192,000	193,417,000	24,680,000	22,513,000	(160,765,000)					(111,000)	(245,000)	(14,000)	(14,000)	(2,911,000)	(4,175,000)	(2,454,000)	(4,681,000)	(336,000)	(4,785,000)	(4,481,000)	(22,921,000)	35,661,000	(19,020,000)	2,093,000	(23,790,000)	31,862,000	(72,822,000)	43,448,000	(8,312,000)
Unrealized loss on Agency MBS, net	(3,158,000)	(8,743,000)
Unrealized gain on Non-Agency MBS, net	262,602,000	18,106,000
Reclassification adjustment for MBS sales included in net income	(2,901,000)
Reclassification adjustment for OTTI included in net income	920,000
Change in accumulated other comprehensive income from MBS	257,463,000	9,363,000
Balance at the end of period	312,954,000	403,185,000						210,197,000		185,192,000	193,417,000	24,680,000	22,513,000	102,757,000					(111,000)	(245,000)	(14,000)	(14,000)	(2,911,000)	(4,175,000)	(2,454,000)	(4,681,000)	(336,000)	(4,785,000)	(4,481,000)	(22,921,000)	35,661,000	(19,020,000)	2,093,000	(23,790,000)	31,862,000	(72,822,000)	43,448,000	(8,312,000)
Changes in the components of the purchase discount on Non-Agency MBS
Balance at beginning of period			(1,228,766,000)	(746,678,000)	(250,479,000)	(228,966,000)
Accretion of discount					9,410,000	10,161,000
Realized credit losses			22,394,000	3,375,000
Purchases			(108,449,000)	(154,943,000)	(7,433,000)	11,726,000
Reclassification adjustment for OTTI			684,000		(684,000)
Net impairment losses recognized in earnings			(920,000)
Unlinking of Linked Transactions			(38,579,000)	(51,423,000)	(6,078,000)	(3,030,000)
Transfers/release of credit reserve			8,918,000	3,816,000	(8,918,000)	(3,816,000)
Balance at end of period			(1,344,718,000)	(945,853,000)	(264,182,000)	(213,925,000)
Purchase discount pertaining to linked transactions designated as accretable purchase discount reallocated to credit reserve														629,000	1,200,000
Sales of MBS
Amount of MBS sold								71,100,000
Gross gains on sale of MBS								3,000,000
MBS Interest Income
Coupon interest								64,008,000	67,707,000					60,860,000	39,537,000
Effective yield adjustment								(10,708,000)	(7,532,000)					9,344,000	10,112,000
Interest on mortgage backed securities								$ 53,300,000	$ 60,175,000					$ 70,204,000	$ 49,649,000