Other Assets - Schedule of Company's Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deposits on future purchases of aircraft	$ 501	$ 501
Investment in Variable Interest Entity	519	330
Investments (Officers' Deferred Compensation Plan)	772	2,685
Deferred Cost	2,721	0
Receivables / Deposits Long Term	12,187	4,875
Other	1,678	350
Total	$ 18,378	$ 8,741