Repurchase Agreements Offsetting (Details) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Offsetting Liabilities [Line Items]
Gross Amount of Recognized Liabilities		$ 2,825,945	$ 2,898,952
Gross Amount Offset in the Balance Sheet		0	0
Net Amount of Liabilities Presented in the Balance Sheet		2,825,945	2,898,952
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities	[1]	(2,825,945)	(2,898,952)
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash		0	0
Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral		$ 0	$ 0

[1] Amounts disclosed for collateral received by or posted to the same counterparty include cash and the fair value of MBS up to and not exceeding the net amount of the asset or liability presented in the balance sheet. The fair value of the actual collateral received by or posted to the same counterparty may exceed the amounts presented.