Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Statements of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ 45,296		$ 57,706
Investing activities:
Purchase of property and equipment	(66,887)		(50,004)
Proceeds from asset dispositions	7,170		37,255
Purchase of short-term investments	(233,606)		(246,375)
Proceeds from sale of short-term investments	182,336		220,249
Refund of deposits on aircraft	6,473		3,150
Payments of deposits on aircraft	(6,837)		(571)
Loan to unconsolidated affiliate	(200)
Net cash used in investing activities	(111,551)		(36,296)
Financing activities:
Proceeds from issuance of Senior Notes due 2019	500,000
Premium and costs to retire debt early	(26,749)
Repayment of Senior Notes due 2018	(300,000)
Debt issuance costs	(6,137)
Proceeds from line of credit	95,500		41,965
Payments on line of credit	(174,500)		(52,997)
Repurchase of common stock	(176)		(1,037)
Net cash provided by financing activities	87,938		(12,069)
Increase in cash	21,683		9,341
Cash, beginning of period	934		2,849
Cash, end of period	22,617		12,190
Parent Company Only (issuer) [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	25,935		48,970
Investing activities:
Purchase of property and equipment	(66,887)		(50,004)
Proceeds from asset dispositions	7,170		37,255
Purchase of short-term investments	(233,606)		(246,375)
Proceeds from sale of short-term investments	182,336		220,249
Refund of deposits on aircraft	6,473		2,579
Payments of deposits on aircraft	(6,837)
Loan to unconsolidated affiliate	(200)
Net cash used in investing activities	(111,551)		(36,296)
Financing activities:
Proceeds from issuance of Senior Notes due 2019	500,000
Premium and costs to retire debt early	(26,749)
Repayment of Senior Notes due 2018	(300,000)
Debt issuance costs	(6,137)
Proceeds from line of credit	95,500		41,965
Payments on line of credit	(174,500)		(52,997)
Repurchase of common stock	(176)		(1,037)
Net cash provided by financing activities	87,938		(12,069)
Increase in cash	2,322		605
Cash, beginning of period	52		552
Cash, end of period	2,374		1,157
Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	19,361	[1]	8,736	[1]
Investing activities:
Purchase of property and equipment		[1]		[1]
Proceeds from asset dispositions		[1]		[1]
Purchase of short-term investments		[1]		[1]
Proceeds from sale of short-term investments		[1]		[1]
Refund of deposits on aircraft		[1]		[1]
Payments of deposits on aircraft		[1]
Loan to unconsolidated affiliate		[1]
Net cash used in investing activities		[1]		[1]
Financing activities:
Proceeds from issuance of Senior Notes due 2019		[1]
Premium and costs to retire debt early		[1]
Repayment of Senior Notes due 2018		[1]
Debt issuance costs		[1]
Proceeds from line of credit		[1]		[1]
Payments on line of credit		[1]		[1]
Repurchase of common stock		[1]		[1]
Net cash provided by financing activities		[1]		[1]
Increase in cash	19,361	[1]	8,736	[1]
Cash, beginning of period	882	[1]	2,297	[1]
Cash, end of period	20,243	[1]	11,033	[1]
Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities
Investing activities:
Purchase of property and equipment
Proceeds from asset dispositions
Purchase of short-term investments
Proceeds from sale of short-term investments
Refund of deposits on aircraft
Payments of deposits on aircraft
Loan to unconsolidated affiliate
Net cash used in investing activities
Financing activities:
Proceeds from issuance of Senior Notes due 2019
Premium and costs to retire debt early
Repayment of Senior Notes due 2018
Debt issuance costs
Proceeds from line of credit
Payments on line of credit
Repurchase of common stock
Net cash provided by financing activities
Increase in cash
Cash, beginning of period
Cash, end of period

[1] Foreign subsidiaries represent minor subsidiaries and are included in the guarantors' subsidiaries amounts.