Financial Derivatives - Schedule of Derivative Instruments, Impact on Results of Operations (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings		$ (3,200)	$ (4,500)
Gains/(losses) on financial derivatives and hedging activities		2,486	(6,782)
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		(5,404)	29,787
Gain (Loss) on Fair Value Hedges Recognized in Earnings		(3,878)	2,889
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives and hedging activities		6,393	(9,522)
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		(3,600)	1,500
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net		300	(1,400)
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]	1,526	(26,898)
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		(29)	(149)
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net		(29)	(149)
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives and hedging activities		6,684	(8,142)
Forward Contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives and hedging activities		(399)	(877)
Future [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives and hedging activities		$ 108	$ (503)

[1] Included in the assessment of hedge effectiveness as of March 31, 2017, but excluded from the amounts in the table, were gains of $3.6 million for the three months ended March 31, 2017, attributable to the fair value of the swaps at the inception of the hedging relationship. Accordingly, the amounts recognized as hedge ineffectiveness for three months ended March 31, 2017 were losses of $0.3 million. The comparable amounts as of March 31, 2016 were losses of $1.5 million for the three months ended March 31, 2016, attributable to the fair value of the swaps at the inception of the hedging relationship and, accordingly, gains of $1.4 million for the three months ended March 31, 2016, attributable to hedge ineffectiveness.