Schedule of Interest Income on MBS and Agency CRT Securities (Details) - MSB - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Coupon interest	$ 86,648	$ 113,478
Net premium amortization	(18,943)	(27,116)
Interest income	$ 67,705	$ 86,362