Commitments and Contingencies - Summary of Rental Expense Incurred Under Leases (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Aircraft	$ 44,908us-gaap_AircraftRental	$ 41,803us-gaap_AircraftRental	$ 36,240us-gaap_AircraftRental
Other	7,790us-gaap_LeaseAndRentalExpense	7,657us-gaap_LeaseAndRentalExpense	8,081us-gaap_LeaseAndRentalExpense
Total	$ 52,698us-gaap_OperatingLeasesRentExpenseNet	$ 49,460us-gaap_OperatingLeasesRentExpenseNet	$ 44,321us-gaap_OperatingLeasesRentExpenseNet

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717

Name:	us-gaap_OperatingLeasesRentExpenseNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration