Income Taxes - Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Foreign tax credits	$ 5,980	$ 0
Deferred revenue	1,631	3,057
Nondeductible accruals	10,107	20,547
Deferred manufacturing credits	258	910
Accrued maintenance	1,991	1,854
Equity compensation	2,392	3,882
Other	5,555	4,026
Valuation allowance	(454)	0
Deferred tax assets	27,460	34,276
Deferred tax liabilities:
Deferred gain (loss) on leases, net	1,605	2,435
Accrued rent	12,055	14,025
Prepaid expenses	754	1,217
Property, plant and equipment	298,703	278,872
Deferred financing costs	225	5,358
Accrued aircraft and engine maintenance	27,258	40,512
Deferred tax liabilities	340,600	342,419
Net deferred tax assets (liabilities)	$ (313,140)	$ (308,143)