Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017		Mar. 31, 2016	Dec. 31, 2016
Derivative [Line Items]
Derivative assets, fair value	$ 272	[1]		$ 28,534
Derivative assets, aggregate notional amount	3,695,000			2,670,000
Derivative liabilities, fair value	(58)	[1]		(6,922)
Derivative liabilities, aggregate notional amount	850,000			1,210,000
Derivative, Notional Amount	$ 4,545,000			$ 3,880,000
Derivative, Average Forward Interest Rate	2.16%			2.18%
Forward Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 2,675,000			$ 2,725,000
Receive-fixed interest rate swap | Interest Rate Swap
Derivative [Line Items]
Derivative, Notional Amount	125,000			425,000
Pay-fixed interest rate swap | Interest Rate Swap
Derivative [Line Items]
Derivative, Notional Amount	4,420,000			$ 3,455,000
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
(Loss) gain on derivative instruments, net	175		$ (48,264)
Not Designated as Hedging Instrument [Member] | Eurodollar Future
Derivative [Line Items]
(Loss) gain on derivative instruments, net	0		(12,186)
Not Designated as Hedging Instrument [Member] | Receive-fixed interest rate swap | Interest Rate Swap
Derivative [Line Items]
(Loss) gain on derivative instruments, net	(134)		10,534
Not Designated as Hedging Instrument [Member] | Pay-fixed interest rate swap | Interest Rate Swap
Derivative [Line Items]
(Loss) gain on derivative instruments, net	$ 309		$ (46,612)

[1] Refer to Note 1 regarding information on a change in the CME rulebook. Amounts reported on the consolidated balance sheet as of March 31, 2017 reflect the netting of the derivative asset or liability with the related collateral received or posted, respectively. The gross amounts comparable to December 31, 2016 for the derivative asset and derivative liabilities as of March 31, 2017 were $24,828 and $(6,133), respectively.