Property and Equipment (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Operating Leases, Future Minimum Payments Receivable [Abstract]
Asset Impairment Charges	$ 0	$ 0	$ 39,075	$ 0
Flight Equipment [Member]
Operating Leases, Future Minimum Payments Receivable [Abstract]
Minimum future lease payments, Due within next 12 months	54,900		54,900		$ 186,800
Minimum future lease payments, Due within next 2 years	213,000		213,000		178,200
Minimum future lease payments, Due within next 3 years	185,000		185,000		152,000
Minimum future lease payments, Due within next 4 years	142,700		142,700		110,100
Minimum future lease payments, Due within next 5 years	108,200		108,200		75,500
CAM [Member] | Flight Equipment [Member]
Property, Plant and Equipment [Line Items]
Leased aircraft, carrying value	$ 1,036,800		$ 1,036,800		$ 889,300