Condensed Consolidating Financial Information (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Condensed Consolidating Statements of Cash Flows
Net cash provided by operating activities	$ 30,103	$ 18,046
Investing activities:
Purchase of property and equipment	(24,936)	(12,520)
Proceeds from asset dispositions	200	6,878
Deposits on aircraft	(419)	281
Proceeds from short-term investments, net	4,417
Purchase of short-term investments, net		(608)
Net cash used in investing activities	(20,738)	(5,969)
Financing activities:
Repurchase of common stock	(1,037)
Proceeds from line of credit	2,400	5,669
Payments on line of credit	(10,000)	(21,790)
Net cash used in financing activities	(8,637)	(16,121)
Increase (decrease) in cash	728	(4,044)
Cash, beginning of period	2,849	5,091
Cash, end of period	3,577	1,047
Parent Company Only (issuer) [Member]
Condensed Consolidating Statements of Cash Flows
Net cash provided by operating activities	31,082	17,830
Investing activities:
Purchase of property and equipment	(24,936)	(12,520)
Proceeds from asset dispositions	200	6,878
Deposits on aircraft	(419)	281
Proceeds from short-term investments, net	4,417
Purchase of short-term investments, net		(608)
Net cash used in investing activities	(20,738)	(5,969)
Financing activities:
Proceeds from line of credit	2,400	5,669
Payments on line of credit	(10,000)	(21,790)
Net cash used in financing activities	(8,637)	(16,121)
Increase (decrease) in cash	1,707	(4,260)
Cash, beginning of period	552	4,313
Cash, end of period	2,259	53
Guarantor Subsidiaries [Member]
Condensed Consolidating Statements of Cash Flows
Net cash provided by operating activities	(979)	216
Financing activities:
Increase (decrease) in cash	(979)	216
Cash, beginning of period	2,297	778
Cash, end of period	1,318	994
Eliminations [Member]
Condensed Consolidating Statements of Cash Flows
Net cash provided by operating activities
Investing activities:
Purchase of property and equipment
Proceeds from asset dispositions
Deposits on aircraft
Proceeds from short-term investments, net
Purchase of short-term investments, net
Net cash used in investing activities
Financing activities:
Repurchase of common stock
Proceeds from line of credit
Payments on line of credit
Net cash used in financing activities
Increase (decrease) in cash
Cash, beginning of period
Cash, end of period