Stockholders' Equity (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Components of accumulated other comprehensive income/(loss)
Accumulated other comprehensive income/(loss)					$ 761,977
Other Comprehensive (Loss)/Income	(3,242)		480,265		(96,315)		745,152
Accumulated other comprehensive income/(loss)	665,662				665,662
Net Unrealized Gain on Available-for-Sale MBS
Components of accumulated other comprehensive income/(loss)
Accumulated other comprehensive income/(loss)	700,871		296,007		824,808		55,491
OCI before reclassifications	31,850		471,741		(89,847)		713,456
Amounts reclassified from AOCI	(15,158)	[1]	(3,130)	[1]	(17,398)	[1]	(4,329)	[1]
Other Comprehensive (Loss)/Income	16,692	[2]	468,611	[2]	(107,245)	[2]	709,127	[2]
Accumulated other comprehensive income/(loss)	717,563		764,618		717,563		764,618
Net Unrealized (Loss)/Gain on Swaps
Components of accumulated other comprehensive income/(loss)
Accumulated other comprehensive income/(loss)	(31,967)		(89,823)		(62,831)		(114,194)
OCI before reclassifications	(19,934)		11,654		10,930		36,025
Amounts reclassified from AOCI	0	[1]	0	[1]	0	[1]	0	[1]
Other Comprehensive (Loss)/Income	(19,934)	[2]	11,654	[2]	10,930	[2]	36,025	[2]
Accumulated other comprehensive income/(loss)	(51,901)		(78,169)		(51,901)		(78,169)
Total AOCI
Components of accumulated other comprehensive income/(loss)
Accumulated other comprehensive income/(loss)	668,904		206,184		761,977		(58,703)
OCI before reclassifications	11,916		483,395		(78,917)		749,481
Amounts reclassified from AOCI	(15,158)	[1]	(3,130)	[1]	(17,398)	[1]	(4,329)	[1]
Other Comprehensive (Loss)/Income	(3,242)	[2]	480,265	[2]	(96,315)	[2]	745,152	[2]
Accumulated other comprehensive income/(loss)	$ 665,662		$ 686,449		$ 665,662		$ 686,449

[1] See separate table below for details about these reclassifications.

[2] For further information regarding changes in OCI, see the Company’s consolidated statement of comprehensive income/(loss).