Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2014 Aircraft	Jun. 30, 2014 Aircraft	Mar. 31, 2014 Aircraft	Sep. 30, 2014 Aircraft	Dec. 31, 2013 Aircraft
Long-term Purchase Commitment [Line Items]
Total aircraft deposits	$ 10.2			$ 10.2
Aggregate estimated probable liability environmental matters	0.2			0.2
Aggregate commitments under operating leases	294.6			294.6
Operational lease payable	12.6			12.6
Lease commitment for aircraft	278.8			278.8
Facility lease commitments	15.8			15.8
Heavy Helicopters [Member]
Long-term Purchase Commitment [Line Items]
Number of aircrafts acquire under contract					6
Number of aircrafts delivered under contract	2	1	1
Option to purchase additional number of aircraft				6
Aircraft purchased				6
2014 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft				35.7
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				$ 129.6