MBS (Details 2) (USD $)	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2014 Security		Sep. 30, 2013		Sep. 30, 2014 Security		Sep. 30, 2013		Dec. 31, 2013
Fair Value
Less than 12 months	$ 576,939,000				$ 576,939,000
12 months or more	2,061,744,000				2,061,744,000
Total	2,638,683,000				2,638,683,000
Unrealized Losses
Less than 12 months					2,810,000
12 months or more					54,004,000
Total					56,814,000
Number of Securities
Less than 12 months (in security)	61				61
12 months or more (in security)	261				261
Unrealized loss on securities					56,814,000				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	905,704,000		700,871,000		752,912,000		824,808,000		824,808,000
Reclassification adjustment for MBS sales included in net income	(13,589,000)		(15,158,000)		(21,180,000)		(17,398,000)
Change in AOCI from MBS	(56,999,000)		16,692,000		95,793,000		(107,245,000)
Balance at end of period	848,705,000		717,563,000		848,705,000		717,563,000		752,912,000
Agency Mortgage Backed Securities
Fair Value
Less than 12 months	480,439,000				480,439,000
12 months or more	2,019,394,000				2,019,394,000
Total	2,499,833,000				2,499,833,000
Unrealized Losses
Less than 12 months					1,823,000
12 months or more					51,861,000
Total					53,684,000
Number of Securities
Less than 12 months (in security)	49				49
12 months or more (in security)	246				246
Unrealized loss on securities					53,684,000				92,285,000
AOCI from MBS:
Unrealized (loss)/gain on mortgage backed securities	(14,937,000)		15,469,000		46,000,000		(152,302,000)
MBS Interest Income
Coupon interest	46,529,000		51,997,000		145,864,000		163,986,000
Effective yield adjustment	(13,463,000)	[1]	(15,839,000)	[1]	(35,860,000)	[1]	(47,004,000)	[1]
Agency MBS interest income	33,066,000		36,158,000		110,004,000		116,982,000
Agency Mortgage Backed Securities | Fannie Mae
Fair Value
Less than 12 months	451,536,000				451,536,000
12 months or more	1,316,459,000				1,316,459,000
Total	1,767,995,000				1,767,995,000
Unrealized Losses
Less than 12 months					1,639,000
12 months or more					30,757,000
Total					32,396,000
Number of Securities
Less than 12 months (in security)	46				46
12 months or more (in security)	143				143
Unrealized loss on securities					32,396,000				55,186,000
Agency Mortgage Backed Securities | Freddie Mac
Fair Value
Less than 12 months	28,903,000				28,903,000
12 months or more	702,935,000				702,935,000
Total	731,838,000				731,838,000
Unrealized Losses
Less than 12 months					184,000
12 months or more					21,104,000
Total					21,288,000
Number of Securities
Less than 12 months (in security)	3				3
12 months or more (in security)	103				103
Unrealized loss on securities					21,288,000				37,099,000
Non-Agency Mortgage Backed Securities
Fair Value
Less than 12 months	96,500,000				96,500,000
12 months or more	42,350,000				42,350,000
Total	138,850,000				138,850,000
Unrealized Losses
Less than 12 months					987,000
12 months or more					2,143,000
Total					3,130,000
Number of Securities
Less than 12 months (in security)	12				12
12 months or more (in security)	15				15
Unrealized loss on securities					3,130,000				3,749,000
Changes in the components of the purchase discount on Non-Agency MBS
MBS linked transactions purchase discount designated as accretable purchase discount reallocated to credit reserve	333,000				218,000
MBS linked transactions purchase discount designated as credit reserve reallocated to accretable purchase discount			0				129,000
AOCI from MBS:
Unrealized (loss)/gain on mortgage backed securities	(28,473,000)		16,381,000		70,973,000		62,455,000
Sales of MBS
Proceeds from Sale of Mortgage Backed Securities (MBS) categorized as Available-for-sale	61,600,000		102,200,000		103,600,000		118,200,000
Gain (Loss) on Sales of Mortgage Backed Securities (MBS)	13,900,000		13,700,000		25,300,000		19,700,000
MBS Interest Income
Coupon interest	52,396,000		62,802,000		162,148,000		196,688,000
Effective yield adjustment	25,478,000	[2]	19,501,000	[2]	78,561,000	[2]	48,128,000	[2]
Agency MBS interest income	77,874,000		82,303,000		240,709,000		244,816,000
Non-Agency Mortgage Backed Securities | Discount Designated as Credit Reserve and OTTI
Changes in the components of the purchase discount on Non-Agency MBS
Balance at beginning of period	(986,842,000)	[3]	(1,264,971,000)	[3]	(1,043,037,000)	[4]	(1,380,506,000)	[4]	(1,380,506,000)	[4]
Accretion of discount	0	[3]	0	[3]	0	[4]	0	[4]
Realized credit losses	20,733,000	[3]	48,642,000	[3]	69,129,000	[4]	137,324,000	[4]
Purchases	(4,200,000)	[3]	(851,000)	[3]	(70,535,000)	[4]	(74,238,000)	[4]
Sales	21,024,000	[3]	27,178,000	[3]	34,780,000	[4]	38,150,000	[4]
Transfers/release of credit reserve	20,185,000	[3]	71,010,000	[3]	80,563,000	[4]	160,278,000	[4]
Balance at end of period	(929,100,000)	[3],[4]	(1,118,992,000)	[3],[4]	(929,100,000)	[3],[4]	(1,118,992,000)	[3],[4]
Non-Agency Mortgage Backed Securities | Accretable Discount
Changes in the components of the purchase discount on Non-Agency MBS
Balance at beginning of period	(436,111,000)	[3],[5]	(396,581,000)	[3],[5]	(460,039,000)	[4],[5]	(371,626,000)	[4],[5]	(371,626,000)	[4],[5]
Accretion of discount	25,504,000	[3],[5]	19,556,000	[3],[5]	78,701,000	[4],[5]	48,305,000	[4],[5]
Realized credit losses	0	[3],[5]	0	[3],[5]	0	[4],[5]	0	[4],[5]
Purchases	272,000	[3],[5]	879,000	[3],[5]	25,314,000	[4],[5]	30,533,000	[4],[5]
Sales	4,169,000	[3],[5]	4,248,000	[3],[5]	10,236,000	[4],[5]	10,158,000	[4],[5]
Transfers/release of credit reserve	(20,185,000)	[3],[5]	(71,010,000)	[3],[5]	(80,563,000)	[4],[5]	(160,278,000)	[4],[5]
Balance at end of period	(426,351,000)	[3],[4],[5]	(442,908,000)	[3],[4],[5]	(426,351,000)	[3],[4],[5]	(442,908,000)	[3],[4],[5]
Non-Agency Mortgage Backed Securities | Non-Agency MBS Expected to Recover Par
Fair Value
Less than 12 months	29,826,000	[6]			29,826,000	[6]
12 months or more	22,309,000	[6]			22,309,000	[6]
Total	52,135,000	[6]			52,135,000	[6]
Unrealized Losses
Less than 12 months					333,000	[6]
12 months or more					1,075,000	[6]
Total					1,408,000	[6]
Number of Securities
Less than 12 months (in security)	3	[6]			3	[6]
12 months or more (in security)	8	[6]			8	[6]
Unrealized loss on securities					1,408,000	[6],[7]			1,357,000	[6],[7]
Non-Agency Mortgage Backed Securities | Non-Agency MBS Expected to Recover Less Than Par
Fair Value
Less than 12 months	66,674,000	[6]			66,674,000	[6]
12 months or more	20,041,000	[6]			20,041,000	[6]
Total	86,715,000	[6]			86,715,000	[6]
Unrealized Losses
Less than 12 months					654,000	[6]
12 months or more					1,068,000	[6]
Total					1,722,000	[6]
Number of Securities
Less than 12 months (in security)	9	[6]			9	[6]
12 months or more (in security)	7	[6]			7	[6]
Unrealized loss on securities					$ 1,722,000	[6],[8]			$ 2,392,000	[6],[8]

[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 reallocated $333,000 of purchase discount designated as accretable purchase discount to Credit Reserve on Non-Agency MBS underlying Linked Transactions during the three months ended September 30, 2014. 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 September 30, 2013.

[4] During the nine months ended September 30, 2014, the Company reallocated $218,000 of purchase discount designated as accretable purchase discount to Credit Reserve on Non-Agency MBS underlying Linked Transactions. In addition, the Company reallocated $129,000 of purchase discount designated as Credit Reserve to accretable purchase discount on Non-Agency MBS underlying Linked Transactions during the nine months ended September 30, 2013.

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

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

[7] Includes RPL/NPL MBS which had a $26.5 million Principal/Current face, $26.7 million amortized cost and $26.6 million fair value at September 30, 2014. At December 31, 2013, RPL/NPL MBS had a $3.9 million Principal/Current face, amortized cost and fair value.

[8] At September 30, 2014 and December 31, 2013, the Company expected to recover approximately 83% and 81%, respectively, of the then-current face amount of Non-Agency MBS.