Derivatives (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013		Jun. 30, 2014	Jun. 30, 2013
Amortization:
Total Amortization	$ (8,854)	$ (9,711)		$ (18,181)	$ (17,985)
Interest Expense | Interest Rate Contract
Interest expense:
Hedge ineffectiveness losses	6	(24)		59	104
Amortization of Deferred Hedge Losses, Accelerated	3	2,027	[1]	3	2,027	[1]
Amortization:
Amortization of loss of designated interest rate derivative	0	404		548	745
Amortization of deferred losses	8,851	7,280		17,630	15,213
Total Amortization	8,854	9,711		18,181	17,985
Total charged to interest expense	8,860	9,687		18,240	18,089
Other income:
Total charged to interest expense	8,860	9,687		18,240	18,089
Other Income | Interest Rate Contract
Amortization:
Total charged to interest expense	0	1,657		681	2,872
Other income:
Mark to market gains on undesignated interest rate derivatives	0	1,657		681	2,872
Total charged to interest expense	$ 0	$ 1,657		$ 681	$ 2,872

[1] For the three and six months ended June 30, 2013, represents accelerated amortization of deferred hedge losses related to two aircraft sold in June 2013.