Commitments and Contingencies - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2017 USD ($) Land_Parcel
Long-term Purchase Commitment [Line Items]
Purchase commitment for aircraft	$ 0
Total aircraft deposits	500,000
Aggregate estimated probable liability environmental matters	$ 150,000
Number of parcels of land exists | Land_Parcel	2
Aggregate commitments under operating leases	$ 194,900,000
Operational lease payable	10,700,000
Lease commitment for aircraft	182,000,000
Facility lease commitments	12,900,000
2018 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	127,000,000
2019 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	129,000,000
2020 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	$ 22,700,000