MBS (Details 2) (USD $)	3 Months Ended				6 Months Ended				12 Months Ended
	Jun. 30, 2014 Security		Jun. 30, 2013		Jun. 30, 2014 Security		Jun. 30, 2013		Dec. 31, 2013
Fair Value
Less than 12 months	$ 436,257,000				$ 436,257,000
12 months or more	2,169,063,000				2,169,063,000
Total	2,605,320,000				2,605,320,000
Unrealized Losses
Less than 12 months					2,175,000
12 months or more					43,049,000
Total					45,224,000
Number of Securities
Less than 12 months (in security)	41				41
12 months or more (in security)	266				266
Unrealized loss on securities					45,224,000				96,034,000
Roll-forward of the credit loss component of OTTI
Credit loss component of OTTI at beginning of period	36,115,000				36,115,000
Additions for credit related OTTI not previously recognized	0				0
Subsequent additional credit related OTTI recorded	0				0
Credit loss component of OTTI at end of period	36,115,000				36,115,000				36,115,000
AOCI from MBS:
Unrealized gain on MBS at beginning of period	819,222,000		942,887,000		752,912,000		824,808,000		824,808,000
Unrealized gain/(loss) on Agency MBS, net	43,094,000		(140,480,000)		60,937,000		(167,771,000)
Unrealized gain/(loss) on Non-Agency MBS, net	50,136,000		(98,282,000)		101,554,000		48,388,000
Reclassification adjustment for MBS sales included in net income	(6,748,000)		(3,254,000)		(9,699,000)		(4,554,000)
Change in AOCI from MBS	86,482,000		(242,016,000)		152,792,000		(123,937,000)
Balance at end of period	905,704,000		700,871,000		905,704,000		700,871,000		752,912,000
Sales of MBS
Gross gains on sale of MBS	7,852,000		4,365,000		11,423,000		5,998,000
Agency MBS
Fair Value
Less than 12 months	417,232,000				417,232,000
12 months or more	2,116,487,000				2,116,487,000
Total	2,533,719,000				2,533,719,000
Unrealized Losses
Less than 12 months					2,047,000
12 months or more					40,963,000
Total					43,010,000
Number of Securities
Less than 12 months (in security)	37				37
12 months or more (in security)	250				250
Unrealized loss on securities					43,010,000				92,285,000
MBS Interest Income
Coupon interest	49,836,000		54,485,000		99,335,000		111,989,000
Effective yield adjustment	(12,227,000)	[1]	(16,448,000)	[1]	(22,397,000)	[1]	(31,165,000)	[1]
Interest on mortgage backed securities	37,609,000		38,037,000		76,938,000		80,824,000
Agency MBS | Fannie Mae.
Fair Value
Less than 12 months	407,252,000				407,252,000
12 months or more	1,383,328,000				1,383,328,000
Total	1,790,580,000				1,790,580,000
Unrealized Losses
Less than 12 months					2,013,000
12 months or more					25,162,000
Total					27,175,000
Number of Securities
Less than 12 months (in security)	35				35
12 months or more (in security)	147				147
Unrealized loss on securities					27,175,000				55,186,000
Agency MBS | Freddie Mac.
Fair Value
Less than 12 months	9,980,000				9,980,000
12 months or more	733,159,000				733,159,000
Total	743,139,000				743,139,000
Unrealized Losses
Less than 12 months					34,000
12 months or more					15,801,000
Total					15,835,000
Number of Securities
Less than 12 months (in security)	2				2
12 months or more (in security)	103				103
Unrealized loss on securities					15,835,000				37,099,000
Non-Agency MBS
Fair Value
Less than 12 months	19,025,000				19,025,000
12 months or more	52,576,000				52,576,000
Total	71,601,000				71,601,000
Unrealized Losses
Less than 12 months					128,000
12 months or more					2,086,000
Total					2,214,000
Number of Securities
Less than 12 months (in security)	4				4
12 months or more (in security)	16				16
Unrealized loss on securities					2,214,000				3,749,000
Changes in the components of the purchase discount on Non-Agency MBS
MBS linked transactions purchase discount designated as credit reserve reallocated to accretable purchase discount	0		116,000		115,000		129,000
Sales of MBS
Amount of MBS sold	26,500,000		9,900,000		42,000,000		16,000,000
Gross gains on sale of MBS	7,900,000		4,400,000		11,400,000		6,000,000
MBS Interest Income
Coupon interest	55,322,000		65,954,000		109,752,000		133,887,000
Effective yield adjustment	25,694,000	[2]	16,644,000	[2]	53,083,000	[2]	28,626,000	[2]
Interest on mortgage backed securities	81,016,000		82,598,000		162,835,000		162,513,000
Non-Agency MBS | Discount Designated as Credit Reserve and OTTI
Changes in the components of the purchase discount on Non-Agency MBS
Balance at beginning of period	(1,041,933,000)	[3]	(1,312,952,000)	[3]	(1,043,037,000)	[3]	(1,380,506,000)	[4]	(1,380,506,000)	[4]
Accretion of discount	0	[3]	0	[3]	0	[3]	0	[4]
Realized credit losses	23,359,000	[3]	38,375,000	[3]	48,396,000	[3]	88,682,000	[4]
Purchases	(3,018,000)	[3]	(49,852,000)	[3]	(66,335,000)	[3]	(73,387,000)	[4]
Sales	10,269,000	[3]	4,689,000	[3]	13,756,000	[3]	10,972,000	[4]
Transfers/release of credit reserve	24,481,000	[3]	54,769,000	[3]	60,378,000	[3]	89,268,000	[4]
Balance at end of period	(986,842,000)	[3]	(1,264,971,000)	[4],[5]	(986,842,000)	[3]	(1,264,971,000)	[4],[5]
Non-Agency MBS | Accretable Discount
Changes in the components of the purchase discount on Non-Agency MBS
Balance at beginning of period	(442,156,000)	[3],[6]	(381,913,000)	[6],[7]	(460,039,000)	[4],[6]	(371,626,000)	[4],[6]	(371,626,000)	[4],[6]
Accretion of discount	25,766,000	[3],[6]	16,698,000	[6],[7]	53,197,000	[4],[6]	28,749,000	[4],[6]
Realized credit losses	0	[3],[6]	0	[6],[7]	0	[4],[6]	0	[4],[6]
Purchases	1,636,000	[3],[6]	18,425,000	[6],[7]	25,042,000	[4],[6]	29,654,000	[4],[6]
Sales	3,124,000	[3],[6]	4,978,000	[6],[7]	6,067,000	[4],[6]	5,910,000	[4],[6]
Transfers/release of credit reserve	(24,481,000)	[3],[6]	(54,769,000)	[6],[7]	(60,378,000)	[4],[6]	(89,268,000)	[4],[6]
Balance at end of period	(436,111,000)	[3],[4],[6]	(396,581,000)	[4],[6],[7]	(436,111,000)	[3],[4],[6]	(396,581,000)	[4],[6],[7]
Non-Agency MBS Expected to Recover Par | Non-Agency MBS
Fair Value
Less than 12 months	1,357,000	[8]			1,357,000	[8]
12 months or more	23,335,000	[8]			23,335,000	[8]
Total	24,692,000	[8]			24,692,000	[8]
Unrealized Losses
Less than 12 months					10,000	[8]
12 months or more					1,124,000	[8]
Total					1,134,000	[8]
Number of Securities
Less than 12 months (in security)	1	[8]			1	[8]
12 months or more (in security)	8	[8]			8	[8]
Unrealized loss on securities					1,134,000	[8]			1,357,000	[8]
Non-Agency MBS Expected to Recover Less Than Par | Non-Agency MBS
Fair Value
Less than 12 months	17,668,000	[8]			17,668,000	[8]
12 months or more	29,241,000	[8]			29,241,000	[8]
Total	46,909,000	[8]			46,909,000	[8]
Unrealized Losses
Less than 12 months					118,000	[8]
12 months or more					962,000	[8]
Total					1,080,000	[8]
Number of Securities
Less than 12 months (in security)	3	[8]			3	[8]
12 months or more (in security)	8	[8]			8	[8]
Unrealized loss on securities					$ 1,080,000	[8],[9]			$ 2,392,000	[8],[9]

[1] Includes amortization of premium paid net of accretion of purchase discount. For Agency MBS, interest income is recorded at an effective yield, which reflects net premium amortization based on actual prepayment activity.

[2] The effective yield adjustment is the difference between the net income calculated using the net yield, which is based on management’s estimates of future cash flows for Non-Agency MBS, less the current coupon yield.

[3] The Company did not reallocate any purchase discount designated as Credit Reserve to accretable purchase discount on Non-Agency MBS underlying Linked Transactions during the three months ended June 30, 2014. The Company reallocated $116,000 of purchase discount designated as Credit Reserve to accretable purchase discount on Non-Agency MBS underlying Linked Transactions during the three months ended June 30, 2013.

[4] In addition, the Company reallocated $115,000 and $129,000 of purchase discount designated as Credit Reserve to accretable purchase discount on Non-Agency MBS underlying Linked Transactions during the six months ended June 30, 2014 and 2013, respectively.

[5] Discount designated as Credit Reserve and amounts related to OTTI are generally not expected to be accreted into interest income. Amounts disclosed at June 30, 2014 reflect Credit Reserve of $942.7 million and OTTI of $44.1 million. Amounts disclosed at December 31, 2013 reflect Credit Reserve of $998.5 million and OTTI of $44.5 million.

[6] Together with coupon interest, accretable purchase discount is recognized as interest income over the life of the security.

[7] Includes principal payments receivable of $1.3 million and $1.1 million at June 30, 2014 and December 31, 2013, respectively, which are not included in the Principal/Current Face.

[8] Based on management’s current estimates of future principal cash flows expected to be received.

[9] At June 30, 2014 and December 31, 2013, the Company expected to recover approximately 82% and 81%, respectively, of the then-current face amount of Non-Agency MBS.