Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	1 Months Ended	0 Months Ended
	Mar. 31, 2015 Land_Parcel	Mar. 31, 2014 Aircraft	Jan. 02, 2015 Aircraft
Long-term Purchase Commitment [Line Items]
Total aircraft deposits	$ 7.4
Aggregate estimated probable liability environmental matters	0.2
Number of parcels of land exists	2
Aggregate commitments under operating leases	305.6
Operational lease payable	38.3
Lease commitment for aircraft	290.8
Facility lease commitments	14.8
2016 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	67.8
2017 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	55.7
2018 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	127.0
2019 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	150.4
Heavy Helicopters [Member]
Long-term Purchase Commitment [Line Items]
Number of aircraft purchased		6
Number of aircrafts delivered	1
Heavy Aircraft [Member]
Long-term Purchase Commitment [Line Items]
Number of aircraft purchased			1
Aggregate purchase price for aircraft			$ 17.7