Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Statements of Cash Flows (Detail) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	$ (8,048)	$ (1,868)
Investing activities:
Purchase of property and equipment	(22,761)	(49,227)
Proceeds from asset dispositions	1,453	21
Purchase of short-term investments	(284,277)	(268,525)
Purchase of restricted investments	(7,705)	0
Proceeds from sale of short-term investments	318,007	354,250
Payments of deposits on aircraft		0
Loan to unconsolidated affiliate	(274)	0
Net cash (used in) investing activities	4,443	36,519
Financing activities:
Debt issuance cost	(874)	0
Proceeds from line of credit	34,295	99,150
Payments on line of credit	(151,795)	(133,150)
Proceeds from Term Loan	130,000	0
Repurchase of common stock	(99)	(256)
Net cash provided by (used in) financing activities	11,527	(34,256)
Effect of exchange rate changes on cash	(239)	0
Increase (decrease) in cash	7,683	395
Cash, beginning of period	8,770	2,596
Cash, end of period	16,453	2,991
Parent Company Only (issuer) [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	(25,451)	(43,328)
Investing activities:
Purchase of property and equipment	(20,580)	(49,227)
Proceeds from asset dispositions	1,453	21
Purchase of short-term investments	(284,277)	(268,525)
Purchase of restricted investments	(7,705)
Proceeds from sale of short-term investments	318,007	354,250
Payments of deposits on aircraft		0
Loan to unconsolidated affiliate	(274)
Net cash (used in) investing activities	6,624	36,519
Financing activities:
Debt issuance cost	(874)
Proceeds from line of credit	34,295	99,150
Payments on line of credit	(151,795)	(133,150)
Proceeds from Term Loan	130,000
Repurchase of common stock	(99)	(256)
Due to/from affiliate, net	17,158	41,079
Net cash provided by (used in) financing activities	28,685	6,823
Effect of exchange rate changes on cash	0
Increase (decrease) in cash	9,858	14
Cash, beginning of period	47	36
Cash, end of period	9,905	50
Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	6,439	33,670
Investing activities:
Purchase of property and equipment		0
Net cash (used in) investing activities	0	0
Financing activities:
Due to/from affiliate, net	(5,631)	(34,699)
Net cash provided by (used in) financing activities	(5,631)	(34,699)
Effect of exchange rate changes on cash	0
Increase (decrease) in cash	808	(1,029)
Cash, beginning of period	1,072	2,100
Cash, end of period	1,880	1,071
Non-Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	10,964	7,790
Investing activities:
Purchase of property and equipment	(2,181)	0
Net cash (used in) investing activities	(2,181)	0
Financing activities:
Due to/from affiliate, net	(11,527)	(6,380)
Net cash provided by (used in) financing activities	(11,527)	(6,380)
Effect of exchange rate changes on cash	(239)
Increase (decrease) in cash	(2,983)	1,410
Cash, beginning of period	7,651	460
Cash, end of period	$ 4,668	$ 1,870

Payments for deposits for purchase of productive assets.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

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Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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The cash outflow from advancing money to an affiliate (an entity that is related but not strictly controlled by the entity).

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The net cash outflow or inflow associated with the acquisition or sale of a business segment during the period.

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The cash outflow to reacquire common stock during the period.

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