Segment Information - Schedule of Financial Information Concerning Reportable Operating Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Total operating revenues, net	$ 146,424	$ 167,136	$ 281,042	$ 331,152
Total segment direct expenses	126,951	152,417	263,464	304,971
Total segment selling, general and administrative expenses	14,247	11,778	27,290	23,451
Total net segment profit	4,228	7,163	(11,713)	6,593
Interest expense	(8,083)	(7,540)	(16,278)	(15,073)
(Loss) earnings before income taxes	(3,150)	117	(26,223)	(7,371)
Reportable Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net	146,424	167,136	281,042	331,152
Total segment direct expenses	127,941	152,493	265,457	305,047
Total segment selling, general and administrative expenses	5,254	4,520	10,192	8,866
Total segment expenses	133,195	157,013	275,649	313,913
Total net segment profit	13,229	10,123	5,393	17,239
Reportable Operating Segments [Member] | Oil and Gas [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net	74,668	83,185	146,399	171,622
Total segment direct expenses	73,681	87,400	155,410	179,316
Total segment selling, general and administrative expenses	1,635	1,605	3,354	3,132
Total net segment profit	(648)	(5,820)	(12,365)	(10,826)
Reportable Operating Segments [Member] | Air Medical [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net	67,222	75,547	122,559	145,607
Total segment direct expenses	50,402	58,997	101,243	116,041
Total segment selling, general and administrative expenses	3,263	2,642	6,144	5,237
Total net segment profit	13,557	13,908	15,172	24,329
Reportable Operating Segments [Member] | Technical Services [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net	4,534	8,404	12,084	13,923
Total segment direct expenses	3,858	6,096	8,804	9,690
Total segment selling, general and administrative expenses	356	273	694	497
Total net segment profit	320	2,035	2,586	3,736
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Other, net	697	4,792	1,761	5,048
Interest expense	(8,083)	(7,540)	(16,278)	(15,073)
Corporate [Member]
Segment Reporting Information [Line Items]
Unallocated selling, general and administrative costs	$ (8,993)	$ (7,258)	$ (17,099)	$ (14,585)