Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Condensed Income Statements, Captions [Line Items]
Operating revenues, net	$ 168,787	$ 150,167	$ 498,400	$ 431,209
Expenses:
Direct expenses	160,200	136,786	471,509	400,250
Selling, general and administrative expenses	16,255	11,401	46,199	38,691
Total operating expenses	176,455	148,187	517,708	438,941
(Gain) loss on disposal of assets	0	(4)	708	3
Equity in loss of unconsolidated affiliate, net	(118)	(438)	(162)	1,556
Operating (loss) income	(7,550)	2,422	(19,854)	(9,291)
Interest expense	8,357	8,027	24,894	24,305
Other income, net	(1,845)	(706)	(436)	(2,474)
Total expenses	6,512	7,321	24,458	21,831
(Loss) earnings before income taxes	(14,062)	(4,899)	(44,312)	(31,122)
Income tax benefit	(2,531)	(1,622)	(8,705)	(9,324)
Net loss	(11,531)	(3,277)	(35,607)	(21,798)
Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Operating revenues, net	(1,290)	(7,953)	(3,096)	(10,773)
Expenses:
Direct expenses	(1,290)	(7,953)	(3,097)	(10,773)
Selling, general and administrative expenses	(4)	(4)	(13)	(14)
Total operating expenses	(1,294)	(7,957)	(3,110)	(10,787)
Operating (loss) income	4	4	14	14
Equity in net income of consolidated subsidiaries	10,381	14,850	18,542	32,093
Interest expense	0		0	0
Other income, net	4	4	14	14
Total expenses	10,385	14,854	18,556	32,107
(Loss) earnings before income taxes	(10,381)	(14,850)	(18,542)	(32,093)
Net loss	(10,381)	(14,850)	(18,542)	(32,093)
Parent Company Only (issuer) [Member]
Condensed Income Statements, Captions [Line Items]
Operating revenues, net	75,654	79,644	233,608	228,973
Expenses:
Direct expenses	83,935	83,727	246,888	238,669
Selling, general and administrative expenses	9,987	8,240	27,129	29,265
Total operating expenses	93,922	91,967	274,017	267,934
(Gain) loss on disposal of assets	0	(4)	729	4
Equity in loss of unconsolidated affiliate, net	(118)	112	(162)	1,040
Operating (loss) income	(18,150)	(12,431)	(40,976)	(40,005)
Equity in net income of consolidated subsidiaries	(10,381)	(14,850)	(18,542)	(32,093)
Interest expense	8,356	8,027	24,888	24,283
Other income, net	(301)	(709)	(359)	(2,486)
Total expenses	(2,326)	(7,532)	5,987	(10,296)
(Loss) earnings before income taxes	(15,824)	(4,899)	(46,963)	(29,709)
Income tax benefit	(4,293)	(1,622)	(11,356)	(7,911)
Net loss	(11,531)	(3,277)	(35,607)	(21,798)
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Operating revenues, net	72,396	70,692	199,823	197,022
Expenses:
Direct expenses	62,045	51,247	175,673	155,434
Selling, general and administrative expenses	3,666	3,141	10,089	9,296
Total operating expenses	65,711	54,388	185,762	164,730
(Gain) loss on disposal of assets		0		(1)
Operating (loss) income	6,685	16,304	14,061	32,293
Interest expense	1	0	2	22
Other income, net		(1)		(2)
Total expenses	1	(1)	2	20
(Loss) earnings before income taxes	6,684	16,305	14,059	32,273
Income tax benefit		0		(1,413)
Net loss	6,684	16,305	14,059	33,686
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Operating revenues, net	22,027	7,784	68,065	15,987
Expenses:
Direct expenses	15,510	9,765	52,045	16,920
Selling, general and administrative expenses	2,606	24	8,994	144
Total operating expenses	18,116	9,789	61,039	17,064
(Gain) loss on disposal of assets	0		(21)	0
Equity in loss of unconsolidated affiliate, net		(550)		516
Operating (loss) income	3,911	(1,455)	7,047	(1,593)
Interest expense	0		4	0
Other income, net	(1,548)		(91)	0
Total expenses	(1,548)		(87)	0
(Loss) earnings before income taxes	5,459	(1,455)	7,134	(1,593)
Income tax benefit	1,762		2,651	0
Net loss	$ 3,697	$ (1,455)	$ 4,483	$ (1,593)