Condensed Consolidating Financial Information - Condensed Consolidating Statements of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 68,105	$ 26,036
Investing activities:
Purchase of property and equipment	(86,092)	(83,187)
Proceeds from asset dispositions	39,822	9,702
Purchase of short-term investments	(314,519)	(167,952)
Proceeds from sale of short-term investments	287,043	194,957
Deposits returned on aircraft	6,908	5,369
Deposits paid on aircraft	(2,693)	(11,176)
Net cash used in investing activities	(69,531)	(52,287)
Financing activities:
Proceeds from line of credit	101,273	91,863
Payments on line of credit	(99,763)	(68,915)
Repurchase of common stock for payroll tax withholding requirements	(1,037)
Net cash provided by financing activities	473	22,948
(Decrease) increase in cash	(953)	(3,303)
Cash, beginning of period	2,849	5,091
Cash, end of period	1,896	1,788
Parent Company Only (issuer) [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	69,104	25,632
Investing activities:
Purchase of property and equipment	(86,092)	(83,187)
Proceeds from asset dispositions	39,822	9,702
Purchase of short-term investments	(314,519)	(167,952)
Proceeds from sale of short-term investments	287,043	194,957
Deposits returned on aircraft	6,908	5,369
Deposits paid on aircraft	(2,693)	(11,176)
Net cash used in investing activities	(69,531)	(52,287)
Financing activities:
Proceeds from line of credit	101,273	91,863
Payments on line of credit	(99,763)	(68,915)
Repurchase of common stock for payroll tax withholding requirements	(1,037)
Net cash provided by financing activities	473	22,948
(Decrease) increase in cash	46	(3,707)
Cash, beginning of period	552	4,313
Cash, end of period	598	606
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(999)	404
Investing activities:
Purchase of property and equipment
Proceeds from asset dispositions
Purchase of short-term investments
Proceeds from sale of short-term investments
Deposits returned on aircraft
Deposits paid on aircraft
Net cash used in investing activities
Financing activities:
Proceeds from line of credit
Payments on line of credit
Repurchase of common stock for payroll tax withholding requirements
Net cash provided by financing activities
(Decrease) increase in cash	(999)	404
Cash, beginning of period	2,297	778
Cash, end of period	1,298	1,182
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) 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
Deposits returned on aircraft
Deposits paid on aircraft
Net cash used in investing activities
Financing activities:
Proceeds from line of credit
Payments on line of credit
Repurchase of common stock for payroll tax withholding requirements
Net cash provided by financing activities
(Decrease) increase in cash
Cash, beginning of period
Cash, end of period