Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Statements of Cash Flows (Detail) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities		$ 799	$ 69,308
Investing activities:
Purchase of property and equipment		(39,908)	(29,502)
Proceeds from asset dispositions		10,998	567
Purchase of short-term investments		(151,436)	(290,469)
Proceeds from sale of short-term investments		148,838	257,454
Payments of deposits on aircraft		(131)	(131)
Net cash used in investing activities		(31,639)	(62,081)
Financing activities:
Proceeds from line of credit		150,800	119,740
Payments on line of credit		(113,300)	(127,240)
Repurchase of common stock for payroll tax withholding requirements		(500)	(2,338)
Net cash provided by (used in) financing activities		37,000	(9,838)
Increase (decrease) in cash		6,160	(2,611)
Cash, beginning of period		2,407	6,270
Cash, end of period		8,567	3,659
Parent Company Only (issuer) [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities		(12,954)	46,696
Investing activities:
Purchase of property and equipment		(39,535)	(29,502)
Proceeds from asset dispositions		10,998	567
Purchase of short-term investments		(151,436)	(290,469)
Proceeds from sale of short-term investments		148,838	257,454
Payments of deposits on aircraft		(131)	(131)
Net cash used in investing activities		(31,266)	(62,081)
Financing activities:
Proceeds from line of credit		150,800	119,740
Payments on line of credit		(113,300)	(127,240)
Repurchase of common stock for payroll tax withholding requirements		(500)	(2,338)
Due to/from affiliate, net		7,214	25,220
Net cash provided by (used in) financing activities		44,214	15,382
Increase (decrease) in cash		(6)	(3)
Cash, beginning of period		46	51
Cash, end of period		40	48
Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	[1]	13,753	22,612
Investing activities:
Purchase of property and equipment	[1]	(373)
Net cash used in investing activities	[1]	(373)
Financing activities:
Due to/from affiliate, net	[1]	(7,214)	(25,220)
Net cash provided by (used in) financing activities	[1]	(7,214)	(25,220)
Increase (decrease) in cash	[1]	6,166	(2,608)
Cash, beginning of period	[1]	2,361	6,219
Cash, end of period	[1]	$ 8,527	$ 3,611

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