Segment Information - Schedule of Financial Information Concerning Reportable Operating Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total operating revenues, net	$ 168,787	$ 150,167	$ 498,400	$ 431,209
Total direct expenses	160,200	136,786	471,509	400,250
Total segment selling, general and administrative expenses	16,255	11,401	46,199	38,691
Total net segment profit	(7,550)	2,422	(19,854)	(9,291)
Interest expense	(8,357)	(8,027)	(24,894)	(24,305)
Loss before income taxes	(14,062)	(4,899)	(44,312)	(31,122)
Reportable Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net	168,787	150,167	498,400	431,209
Total direct expenses	160,082	136,348	471,347	401,806
Total segment selling, general and administrative expenses	8,343	4,622	24,795	14,813
Total segment direct and selling, general and administrative expenses	168,425	140,970	496,142	416,619
Total net segment profit	362	9,197	2,258	14,590
Reportable Operating Segments [Member] | Oil and Gas [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net	93,338	75,700	286,046	222,098
Total direct expenses	94,832	81,467	285,818	236,878
Total segment selling, general and administrative expenses	4,321	1,148	13,642	4,501
Total net segment profit	(5,815)	(6,915)	(13,414)	(19,281)
Reportable Operating Segments [Member] | Air Medical [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net	70,192	70,280	194,331	192,840
Total direct expenses	60,358	51,120	170,966	152,363
Total segment selling, general and administrative expenses	3,666	3,136	10,087	9,280
Total net segment profit	6,168	16,024	13,278	31,197
Reportable Operating Segments [Member] | Technical Services [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net	5,257	4,187	18,023	16,271
Total direct expenses	4,892	3,761	14,563	12,565
Total segment selling, general and administrative expenses	356	338	1,066	1,032
Total net segment profit	9	88	2,394	2,674
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Other, net	1,845	710	(272)	2,471
Interest expense	(8,357)	(8,027)	(24,894)	(24,305)
Corporate [Member]
Segment Reporting Information [Line Items]
Unallocated selling, general and administrative costs	$ (7,912)	$ (6,779)	$ (21,404)	$ (23,878)