Financial Derivatives - Schedule of Derivative Instruments, Impact on Results of Operations (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings		$ (16,400)	$ (22,800)	$ (19,700)
Gains/(losses) on financial derivatives and hedging activities		2,311	2,531	(21,646)
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		(20,322)	3,100	14,520
Gain (Loss) on Fair Value Hedges Recognized in Earnings		5,043	9,065	11,791
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives and hedging activities		(2,379)	(5,983)	(33,427)
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		5,200	9,200	11,600
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net		200	100	(200)
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	[1]	25,365	5,965	(2,729)
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Cash Flow Hedge Ineffectiveness		(353)	(551)	(10)
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net		(353)	(551)	(10)
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives and hedging activities		(1,991)	(3,204)	(31,101)
Forward Contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives and hedging activities		(226)	(2,440)	(1,842)
Future [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives and hedging activities		$ (162)	$ (339)	$ (484)

[1] Included in the assessment of hedge effectiveness as of December 31, 2016, but excluded from the amounts in the table, were losses of $5.2 million for the year ended December 31, 2016, attributable to the fair value of the swaps at the inception of the hedging relationship. Accordingly, the amounts recognized as hedge ineffectiveness for the year ended December 31, 2016 were gains of $0.2 million. The comparable amounts as of December 31, 2015 were losses of $9.2 million for the year ended December 31, 2015, attributable to the fair value of the swaps at the inception of the hedging relationship and, accordingly, gains of $0.1 million for the year ended December 31, 2015, attributable to hedge ineffectiveness. The comparable amounts as of December 31, 2014 were losses of $11.6 million for the year ended December 31, 2014, attributable to the fair value of the swaps at the inception of the hedging relationships and, accordingly, losses of $0.2 million for the year ended December 31, 2014, attributable to hedge ineffectiveness.