Property and Equipment (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Operating Leases, Future Minimum Payments Receivable [Abstract]
Asset Impairment Charges	$ 0	$ 39,075	$ 0	$ 39,075
Flight Equipment [Member]
Operating Leases, Future Minimum Payments Receivable [Abstract]
Minimum future lease payments, Due within next 12 months	125,900		125,900		$ 222,400
Minimum future lease payments, Due within next 2 years	227,000		227,000		195,500
Minimum future lease payments, Due within next 3 years	182,500		182,500		150,500
Minimum future lease payments, Due within next 4 years	131,900		131,900		99,800
Minimum future lease payments, Due within next 5 years	118,800		118,800		90,700
CAM [Member] | Flight Equipment [Member]
Property, Plant and Equipment [Line Items]
Leased aircraft, carrying value	$ 1,274,300		$ 1,274,300		$ 1,097,600