Summary of Significant Accounting Policies - Schedule of Types of Contract Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Operating revenues	$ 263,605	$ 240,610
Contract Revenue [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	263,495	240,552
Contract Revenue [Member] | Flight Operations Member
Disaggregation of Revenue [Line Items]
Operating revenues	$ 263,495	123,375
Contract Revenue [Member] | Aircraft Lease [Member]
Disaggregation of Revenue [Line Items]
Operating revenues		$ 117,177