Financial Derivatives - Schedule of Derivative Instruments, Impact on Results of Operations (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings		$ (4,000)	$ (5,700)	$ (12,900)	$ (16,800)
(Losses)/gains on financial derivatives and hedging activities		(1,601)	(9,568)	(13,079)	939
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		(10,550)	15,834	35,778	13,356
Gain (Loss) on Fair Value Hedges Recognized in Earnings		726	3,188	5,716	9,026
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives and hedging activities		(2,259)	(12,699)	(18,473)	(7,663)
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		1,000	2,900	4,200	8,600
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net		200	(300)	(1,500)	(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]	11,276	(12,646)	(30,062)	(4,330)
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		(68)	(57)	(322)	(424)
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net		(68)	(57)	(322)	(424)
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives and hedging activities		(2,333)	(11,421)	(16,820)	(5,213)
Forward Contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives and hedging activities		79	(966)	(789)	(2,108)
Future [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives and hedging activities		$ (5)	$ (312)	$ (864)	$ (342)

[1] Included in the assessment of hedge effectiveness as of September 30, 2016, but excluded from the amounts in the table, were losses of $1.0 million and $4.2 million for the three and nine months ended September 30, 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 three and nine months ended September 30, 2016 were losses of $0.2 million and gains of $1.5 million, respectively. The comparable amounts as of September 30, 2015 were losses of $2.9 million and $8.6 million for the three and nine months ended September 30, 2015, attributable to the fair value of the swaps at the inception of the hedging relationship and, accordingly, gains of $0.3 million and $0.4 million for the three and nine months ended September 30, 2015, attributable to hedge ineffectiveness.