Summary of Significant Accounting Policies (Details) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2018 USD ($) financial_institution	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 USD ($) financial_institution Entity segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Accounting Policies [Abstract]
Number of Operating Segments | segment										1
Property, Plant and Equipment [Line Items]
Revenues, As Previously Reported											$ 796,620	$ 772,958	$ 819,202	$ 818,602
Number of Major Financial Institutions | financial_institution	3									3
Gain (Loss) on Disposition of Property Plant Equipment									$ 39,126	$ 36,766	55,167	39,126	58,017	23,146
Revenues	$ 292,566	$ 190,829	$ 204,276	$ 202,680	$ 196,643	$ 213,053	$ 237,059	$ 205,032		$ 890,351	$ 851,787	$ 812,084	$ 877,219	$ 841,748
Passenger Aircraft
Property, Plant and Equipment [Line Items]
Estimated useful life										25 years
Estimated residual value	15.00%									15.00%
Freighter Aircraft | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life										30 years
Estimated residual value	5.00%									5.00%
Freighter Aircraft | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life										35 years
Estimated residual value	10.00%									10.00%
Flight Equipment | Minimum | Property Subject to Operating Lease
Property, Plant and Equipment [Line Items]
Operating Leases, Term of Contract										3 years
Flight Equipment | Maximum | Property Subject to Operating Lease
Property, Plant and Equipment [Line Items]
Operating Leases, Term of Contract										7 years
Variable Interest Entity, Primary Beneficiary
Property, Plant and Equipment [Line Items]
Number of VIE's consolidated | Entity										4