MBS (Details) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Information about MBS
Minimum term of fixed rate mortgages underlying MBS	15 years
Principal/ Current Face	$ 11,828,521,000		$ 11,892,957,000
Purchase Premiums	238,272,000		227,533,000
Accretable Purchase Discounts	(436,185,000)		(460,126,000)
Discount Designated as Credit Reserve and OTTI	(986,842,000)	[1]	(1,043,037,000)	[1]
Amortized Cost	10,645,084,000	[2]	10,618,446,000	[2]
Fair Value	11,550,788,000		11,371,358,000
Gross Unrealized Gains	950,928,000		848,946,000
Gross Unrealized Losses	(45,224,000)		(96,034,000)
Net Unrealized Gain/(Loss)	905,704,000		752,912,000
Principal payments receivable	1,300,000		1,100,000
Agency MBS
Information about MBS
Principal/ Current Face	6,235,147,000		6,276,919,000
Purchase Premiums	237,748,000		226,895,000
Accretable Purchase Discounts	(74,000)		(87,000)
Discount Designated as Credit Reserve and OTTI	0	[1]	0	[1]
Amortized Cost	6,474,139,000	[2]	6,504,846,000	[2]
Fair Value	6,549,451,000		6,519,221,000
Gross Unrealized Gains	118,322,000		106,660,000
Gross Unrealized Losses	(43,010,000)		(92,285,000)
Net Unrealized Gain/(Loss)	75,312,000		14,375,000
Agency MBS | Fannie Mae.
Information about MBS
Principal/ Current Face	5,128,686,000		5,092,410,000
Purchase Premiums	195,467,000		181,710,000
Accretable Purchase Discounts	(74,000)		(87,000)
Discount Designated as Credit Reserve and OTTI	0	[1]	0	[1]
Amortized Cost	5,324,079,000	[2]	5,274,033,000	[2]
Fair Value	5,403,241,000		5,315,363,000
Gross Unrealized Gains	106,337,000		96,516,000
Gross Unrealized Losses	(27,175,000)		(55,186,000)
Net Unrealized Gain/(Loss)	79,162,000		41,330,000
Agency MBS | Freddie Mac.
Information about MBS
Principal/ Current Face	1,094,460,000		1,171,841,000
Purchase Premiums	42,075,000		44,967,000
Accretable Purchase Discounts	0		0
Discount Designated as Credit Reserve and OTTI	0	[1]	0	[1]
Amortized Cost	1,137,853,000	[2]	1,217,927,000	[2]
Fair Value	1,133,670,000		1,190,670,000
Gross Unrealized Gains	11,652,000		9,842,000
Gross Unrealized Losses	(15,835,000)		(37,099,000)
Net Unrealized Gain/(Loss)	(4,183,000)		(27,257,000)
Agency MBS | Ginnie Mae.
Information about MBS
Principal/ Current Face	12,001,000		12,668,000
Purchase Premiums	206,000		218,000
Accretable Purchase Discounts	0		0
Discount Designated as Credit Reserve and OTTI	0	[1]	0	[1]
Amortized Cost	12,207,000	[2]	12,886,000	[2]
Fair Value	12,540,000		13,188,000
Gross Unrealized Gains	333,000		302,000
Gross Unrealized Losses	0		0
Net Unrealized Gain/(Loss)	333,000		302,000
Non-Agency MBS
Information about MBS
Principal/ Current Face	5,593,374,000		5,616,038,000
Purchase Premiums	524,000		638,000
Accretable Purchase Discounts	(436,111,000)		(460,039,000)
Discount Designated as Credit Reserve and OTTI	(986,842,000)	[1]	(1,043,037,000)	[1]
Amortized Cost	4,170,945,000	[2]	4,113,600,000	[2]
Fair Value	5,001,337,000		4,852,137,000
Gross Unrealized Gains	832,606,000		742,286,000
Gross Unrealized Losses	(2,214,000)		(3,749,000)
Net Unrealized Gain/(Loss)	830,392,000		738,537,000
Credit Reserve	942,700,000		998,500,000
OTTI	44,100,000		44,500,000
Non-Agency MBS | Non-Agency MBS Expected to Recover Par
Information about MBS
Principal/ Current Face	313,136,000	[3]	234,187,000	[3]
Purchase Premiums	524,000	[3]	638,000	[3]
Accretable Purchase Discounts	(29,593,000)	[3]	(24,450,000)	[3]
Discount Designated as Credit Reserve and OTTI	0	[1],[3]	0	[1],[3]
Amortized Cost	284,067,000	[2],[3]	210,375,000	[2],[3]
Fair Value	310,586,000	[3]	230,738,000	[3]
Gross Unrealized Gains	27,653,000	[3]	21,720,000	[3]
Gross Unrealized Losses	(1,134,000)	[3]	(1,357,000)	[3]
Net Unrealized Gain/(Loss)	26,519,000	[3]	20,363,000	[3]
Non-Agency MBS | Non-Agency MBS Expected to Recover Less Than Par
Information about MBS
Principal/ Current Face	5,280,238,000	[3],[4]	5,381,851,000	[3],[4]
Purchase Premiums	0	[3],[4]	0	[3],[4]
Accretable Purchase Discounts	(406,518,000)	[3],[4]	(435,589,000)	[3],[4]
Discount Designated as Credit Reserve and OTTI	(986,842,000)	[1],[3],[4]	(1,043,037,000)	[1],[3],[4]
Amortized Cost	3,886,878,000	[2],[3],[4]	3,903,225,000	[2],[3],[4]
Fair Value	4,690,751,000	[3],[4]	4,621,399,000	[3],[4]
Gross Unrealized Gains	804,953,000	[3],[4]	720,566,000	[3],[4]
Gross Unrealized Losses	(1,080,000)	[3],[4]	(2,392,000)	[3],[4]
Net Unrealized Gain/(Loss)	$ 803,873,000	[3],[4]	$ 718,174,000	[3],[4]
Percentage of current face amount of non-agency MBS to be recovered	82.00%		81.00%

[1] 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.

[2] 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.

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

[4] 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.