Financial Derivatives - Schedule of Derivative Instruments, Impact on Results of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives and hedging activities	$ (9,568)	$ 808	$ 939	$ (12,468)
Designated as Hedging Instrument [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	15,834	(2,549)	13,356	4,019
Gain (Loss) on Fair Value Hedges Recognized in Earnings	3,188	3,061	9,026	9,029
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives and hedging activities	(12,756)	(2,253)	(8,087)	(21,497)
Interest Rate Swap [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Components Included from Assessment of Interest Rate Fair Value Hedge Effectiveness	2,900	2,900	8,600	8,700
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net	(300)	(200)	380	(300)
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	(12,646)	5,610	(4,330)	5,010
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives and hedging activities	(11,478)	(2,074)	(5,637)	(19,748)
Forward Contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives and hedging activities	(966)	(210)	(2,108)	(1,297)
Future [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives and hedging activities	$ (312)	$ 31	$ (342)	$ (452)