Derivatives Volume of Activity (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($)
Derivative [Line Items]
Beginning of Period Notional Amount	$ 3,880,000
Notional Amount of Derivative Instruments Added	1,400,000
Notional Amount of Derivative Instruments Terminated	(735,000)
End of Period Notional Amount	4,545,000
Forward Contracts [Member]
Derivative [Line Items]
Beginning of Period Notional Amount	2,725,000
End of Period Notional Amount	2,675,000
Interest Rate Swap | Receive-fixed interest rate swap
Derivative [Line Items]
Beginning of Period Notional Amount	425,000
Notional Amount of Derivative Instruments Added	0
Notional Amount of Derivative Instruments Terminated	(300,000)
End of Period Notional Amount	125,000
Interest Rate Swap | Pay-fixed interest rate swap
Derivative [Line Items]
Beginning of Period Notional Amount	3,455,000
Notional Amount of Derivative Instruments Added	1,400,000
Notional Amount of Derivative Instruments Terminated	(435,000)
End of Period Notional Amount	$ 4,420,000