Income Taxes - Reconciliation of GAAP Net Income to Estimated REIT Taxable Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Tax Disclosure [Abstract]
GAAP net loss	$ (279,475)	$ (125,469)
Book to tax differences:
Net book to tax differences on Non-Agency Securities	(4,125)	0
Changes in interest rate contracts	315,811	167,407
Gains on Security Sales	(1,891)	(6,544)
Amortization of deferred hedging costs	(9,232)	(1,877)
Other	3	4
Estimated taxable income	$ 21,091	$ 33,521