MBS (Details 2) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended		6 Months Ended						3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2012 Security	Jun. 30, 2011	Jun. 30, 2012 Security	Jun. 30, 2011	Jun. 30, 2012 Discount Designated as Credit Reserve and OTTI	Jun. 30, 2011 Discount Designated as Credit Reserve and OTTI	Jun. 30, 2012 Discount Designated as Credit Reserve and OTTI	Jun. 30, 2011 Discount Designated as Credit Reserve and OTTI	Jun. 30, 2012 Accretable Discount	Jun. 30, 2011 Accretable Discount	Jun. 30, 2012 Accretable Discount	Jun. 30, 2011 Accretable Discount	Jun. 30, 2012 Low end of range D	Jun. 30, 2012 Low end of range D	Jun. 30, 2012 Agency MBS Security	Jun. 30, 2011 Agency MBS	Jun. 30, 2012 Agency MBS Security	Jun. 30, 2011 Agency MBS	Jun. 30, 2012 Agency MBS Fannie Mae. Security	Dec. 31, 2011 Agency MBS Fannie Mae.	Jun. 30, 2012 Agency MBS Freddie Mac. Security	Dec. 31, 2011 Agency MBS Freddie Mac.	Jun. 30, 2012 Non-Agency MBS Security	Jun. 30, 2011 Non-Agency MBS	Jun. 30, 2012 Non-Agency MBS Security	Jun. 30, 2011 Non-Agency MBS	Jun. 30, 2012 Non-Agency MBS Weighted average	Jun. 30, 2011 Non-Agency MBS Weighted average	Jun. 30, 2012 Non-Agency MBS Weighted average	Jun. 30, 2011 Non-Agency MBS Weighted average	Jun. 30, 2012 Non-Agency MBS Low end of range	Jun. 30, 2011 Non-Agency MBS Low end of range	Jun. 30, 2012 Non-Agency MBS Low end of range	Jun. 30, 2011 Non-Agency MBS Low end of range	Jun. 30, 2012 Non-Agency MBS High end of range	Jun. 30, 2011 Non-Agency MBS High end of range	Jun. 30, 2012 Non-Agency MBS High end of range	Jun. 30, 2011 Non-Agency MBS High end of range	Jun. 30, 2012 Non-Agency MBS Rated AAA Security	Dec. 31, 2011 Non-Agency MBS Rated AAA	Jun. 30, 2012 Non-Agency MBS Rated AA Security	Dec. 31, 2011 Non-Agency MBS Rated AA	Jun. 30, 2012 Non-Agency MBS Rated A Security	Dec. 31, 2011 Non-Agency MBS Rated A	Jun. 30, 2012 Non-Agency MBS Rated BBB Security	Dec. 31, 2011 Non-Agency MBS Rated BBB	Jun. 30, 2012 Non-Agency MBS Rated BB Security	Dec. 31, 2011 Non-Agency MBS Rated BB	Jun. 30, 2012 Non-Agency MBS Rated B Security	Dec. 31, 2011 Non-Agency MBS Rated B	Jun. 30, 2012 Non-Agency MBS Rated CCC Security	Dec. 31, 2011 Non-Agency MBS Rated CCC	Jun. 30, 2012 Non-Agency MBS Rated CC Security	Dec. 31, 2011 Non-Agency MBS Rated CC	Jun. 30, 2012 Non-Agency MBS Rated C Security	Dec. 31, 2011 Non-Agency MBS Rated C	Jun. 30, 2012 Non-Agency MBS Unrated and other Security	Dec. 31, 2011 Non-Agency MBS Unrated and other
Fair Value
Less than 12 months (in security)	$ 1,238,680,000		$ 1,238,680,000												$ 617,681,000		$ 617,681,000		$ 599,290,000		$ 18,391,000		$ 620,999,000		$ 620,999,000														$ 17,587,000						$ 3,936,000		$ 9,506,000		$ 8,863,000		$ 91,881,000		$ 43,890,000		$ 184,805,000		$ 260,531,000
12 months or more (in security)	1,823,922,000		1,823,922,000												50,774,000		50,774,000		47,942,000		2,832,000		1,773,148,000		1,773,148,000																34,000		20,895,000		23,254,000		72,348,000		174,843,000		237,592,000		185,561,000		482,007,000		576,614,000
Total	3,062,602,000		3,062,602,000												668,455,000		668,455,000		647,232,000		21,223,000		2,394,147,000		2,394,147,000														17,587,000		34,000		20,895,000		27,190,000		81,854,000		183,706,000		329,473,000		229,451,000		666,812,000		837,145,000
Unrealized Losses
Less than 12 months	12,983,000		12,983,000												2,095,000		2,095,000		2,064,000		31,000		10,888,000		10,888,000														114,000						1,000		345,000		73,000		1,366,000		633,000		2,249,000		6,107,000
12 months or more	114,459,000		114,459,000												772,000		772,000		754,000		18,000		113,687,000		113,687,000																14,000		2,597,000		1,567,000		4,420,000		11,004,000		15,030,000		13,065,000		27,542,000		38,448,000
Total	127,442,000		127,442,000												2,867,000		2,867,000		2,818,000		49,000		124,575,000		124,575,000														114,000		14,000		2,597,000		1,568,000		4,765,000		11,077,000		16,396,000		13,698,000		29,791,000		44,555,000
Number of Securities
Less than 12 months	95		95												40		40		38		2		55		55														2						1		2		1		7		3		13		26
12 months or more	157		157												11		11		10		1		146		146																1		1		7		9		14		24		14		33		43
Credit-related OTTI losses recognized during the period	280,000	2,392,000	1,200,000	2,392,000																			280,000	2,400,000	1,200,000	2,400,000
OTTI charges recorded
Total OTTI losses		(637,000)	(879,000)	(637,000)
OTTI reclassified from other comprehensive income	280,000	1,755,000	321,000	1,755,000
OTTI recognized in earnings	280,000	2,392,000	1,200,000	2,392,000																			280,000	2,400,000	1,200,000	2,400,000
Roll-forward of the credit loss component of OTTI
Credit loss component of OTTI at beginning of period	35,835,000		34,915,000
Additions for credit related OTTI not previously recognized			458,000
Subsequent additional credit related OTTI recorded	280,000		742,000
Credit loss component of OTTI at end of period	36,115,000		36,115,000
Significant inputs considered and assumptions made in determining the measurement of the component of OTTI recorded in earnings
Credit enhancement (as a percent)																											4.00%	3.80%	3.26%	3.80%					12.10%	13.30%	16.50%	13.30%
Projected CPR (as a percent)																											9.80%	10.80%	9.90%	10.80%	9.10%	1.90%	9.10%	1.90%	11.00%	12.00%	13.30%	12.00%
Projected Loss Severity (as a percent)																											52.20%	48.40%	55.50%	48.40%	45.70%	41.90%	45.90%	41.90%	55.40%	60.00%	60.00%	60.00%
60+ days delinquent (as a percent)																											28.60%	20.90%	24.40%	20.90%	21.00%	7.30%	18.20%	7.30%	32.40%	32.40%	32.40%	32.40%
Number of days considered to classify loans delinquent													60	60
Changes in the components of the purchase discount on Non-Agency MBS
Balance at beginning of period					(1,344,718,000)	(945,853,000)	(1,228,766,000)	(746,678,000)	(264,182,000)	(213,925,000)	(250,479,000)	(228,966,000)
Accretion of discount									9,881,000	12,161,000	19,291,000	22,322,000
Realized credit losses					35,521,000	6,502,000	57,915,000	9,877,000
Purchases					(139,934,000)	(176,571,000)	(248,383,000)	(331,514,000)	(1,004,000)	(14,563,000)	(8,437,000)	(2,837,000)
Reclassification adjustment for OTTI					182,000	101,000	866,000	101,000	(182,000)	(101,000)	(866,000)	(101,000)
Net impairment losses recognized in earnings					(280,000)	(2,392,000)	(1,200,000)	(2,392,000)
Unlinking of Linked Transactions					(83,000)	(54,647,000)	(38,662,000)	(106,070,000)	(1,090,000)	(8,532,000)	(7,168,000)	(11,562,000)
Transfers/release of credit reserve					8,560,000	(2,030,000)	17,478,000	1,786,000	(8,560,000)	2,030,000	(17,478,000)	(1,786,000)
Balance at end of period					(1,440,752,000)	(1,174,890,000)	(1,440,752,000)	(1,174,890,000)	(265,137,000)	(222,930,000)	(265,137,000)	(222,930,000)
Accumulated other comprehensive income from MBS:
Balance at the beginning of the period	312,954,000	403,185,000	55,491,000	393,822,000													216,256,000		173,714,000	193,417,000	24,961,000	22,513,000			(160,765,000)														(62,000)	(245,000)	(14,000)	(14,000)	(2,597,000)	(4,175,000)	(1,146,000)	(4,681,000)	(4,592,000)	(4,785,000)	(2,481,000)	(22,921,000)	39,361,000	(19,020,000)	3,914,000	(23,790,000)	25,182,000	(72,822,000)	39,415,000	(8,312,000)
Unrealized (loss)/gain on Agency MBS, net	(11,170,000)	46,456,000	(14,328,000)	37,713,000
Unrealized (loss)/gain on Non-Agency MBS, net	(6,057,000)	(159,657,000)	256,545,000	(141,551,000)
Reclassification adjustment for MBS sales included in net income			(2,901,000)
Reclassification adjustment for OTTI included in net income	280,000	2,392,000	1,200,000	2,392,000
Change in accumulated other comprehensive income from MBS	(240,516,000)	(101,466,000)	(240,516,000)	(101,466,000)
Balance at the end of period	296,007,000	292,376,000	296,007,000	292,376,000											199,027,000		199,027,000		173,714,000	193,417,000	24,961,000	22,513,000	96,980,000		96,980,000														(62,000)	(245,000)	(14,000)	(14,000)	(2,597,000)	(4,175,000)	(1,146,000)	(4,681,000)	(4,592,000)	(4,785,000)	(2,481,000)	(22,921,000)	39,361,000	(19,020,000)	3,914,000	(23,790,000)	25,182,000	(72,822,000)	39,415,000	(8,312,000)
Purchase discount pertaining to linked transactions designated as accretable purchase discount reallocated to credit reserve																								366,000	629,000	799,000
Sales of MBS
Amount of MBS sold																	71,100,000
Gross gains on sale of MBS																	3,000,000
MBS Interest Income
Coupon interest															61,976,000	74,343,000	125,984,000	142,049,000					66,144,000	53,988,000	127,004,000	93,525,000
Effective yield adjustment															(12,426,000)	(8,361,000)	(23,134,000)	(15,892,000)					9,810,000	12,112,000	19,154,000	22,224,000
Interest on mortgage backed securities															$ 49,550,000	$ 65,982,000	$ 102,850,000	$ 126,157,000					$ 75,954,000	$ 66,100,000	$ 146,158,000	$ 115,749,000