Derivatives (Details 2) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended
	Jun. 30, 2013 Aircraft	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Number of Aircraft Sold	2
Amortization:
Total Amortization		$ (34,979)		$ (33,265)	$ (30,777)
Interest Expense | Interest Rate Contract
Interest Expense:
Hedge ineffectiveness losses		738		(371)	(2,893)
Amortization:
Accelerated amortization of deferred losses		(78)	[1]	(2,931)	0
Amortization of loss of designated interest rate derivative		548		1,590	101
Amortization of deferred losses		34,419		28,744	30,676
Total Amortization		34,979		33,265	30,777
Total charged to interest expense		35,717		33,636	33,670
Other Income (Expense) - Other:
Total charged to other income (expense) - other		35,717		33,636	33,670
Other Income | Interest Rate Contract
Amortization:
Total charged to interest expense		1,130		4,754	597
Other Income (Expense) - Other:
Mark to market gains on undesignated interest rate derivatives		1,130		4,754	597
Total charged to other income (expense) - other		$ 1,130		$ 4,754	$ 597

[1] For the year ended December 31, 2013, includes accelerated amortization of deferred hedge losses related to two aircraft sold in June 2013.