Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 02, 2015 Aircraft
Long-term Purchase Commitment [Line Items]
Aircraft and real estate rental expense	$ 52,698,000	$ 49,460,000	$ 44,321,000
Aggregate amount of guarantees and bonds	1,100,000
Total aircraft deposits	8,305,000	12,863,000
Aggregate estimated probable liability environmental matters	200,000
Affiliated Entity [Member]
Long-term Purchase Commitment [Line Items]
Aircraft and real estate rental expense	500,000	600,000	300,000
Minimum [Member]
Long-term Purchase Commitment [Line Items]
Guarantee expiration period	2015-03
Maximum [Member]
Long-term Purchase Commitment [Line Items]
Guarantee expiration period	2015-11
Heavy Aircraft [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	89,300,000
Number of aircraft purchased	5
Number of aircrafts acquire under contract		6
Option to purchase additional number of aircrafts	6
Heavy Aircraft [Member] | Subsequent Event [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft				17,700,000
Number of aircraft purchased				1
Medium Aircraft [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	14,900,000
Number of aircraft purchased	2
Fixed Wing Aircraft [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	3,500,000
Number of aircraft purchased	1
2015 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	17,700,000
2016 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	67,800,000
2017 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	55,700,000
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	$ 150,400,000