Business Segments and Geographic Areas - Schedule of Financial Information Concerning Reportable Operating Segments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total operating revenues	$ 148,336	$ 150,167	$ 146,424	$ 134,618	$ 144,853	$ 158,093	$ 167,136	$ 164,016	$ 579,545	$ 634,098	$ 804,228
Total segment direct expenses									546,699	592,550	687,050
Total segment selling, general and administrative expenses									53,817	44,418	46,422
Total net segment profit									(22,022)	224	70,111
Interest expense									(32,183)	(30,644)	(29,066)
(Loss) earnings before income taxes	$ (20,319)	$ (4,899)	$ (3,150)	$ (23,073)	$ (12,012)	$ (7,766)	$ 117	$ (7,488)	(51,441)	(27,149)	43,256
Reportable Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating revenues									579,545	634,098	804,228
Total segment direct expenses									547,084	592,399	687,356
Total segment selling, general and administrative expenses									19,746	18,808	17,771
Total segment expenses									566,830	611,207	705,127
Total net segment profit									12,715	22,891	99,101
Reportable Operating Segments [Member] | Oil and Gas [Member]
Segment Reporting Information [Line Items]
Total operating revenues									298,398	324,129	459,611
Total segment direct expenses									321,272	344,640	411,757
Total segment selling, general and administrative expenses									5,899	6,739	6,511
Total net segment profit									(28,773)	(27,250)	41,343
Reportable Operating Segments [Member] | Air Medical [Member]
Segment Reporting Information [Line Items]
Total operating revenues									257,273	281,868	312,775
Total segment direct expenses									208,987	227,877	246,487
Total segment selling, general and administrative expenses									12,442	10,968	10,455
Total net segment profit									35,844	43,023	55,833
Reportable Operating Segments [Member] | Technical Services [Member]
Segment Reporting Information [Line Items]
Total operating revenues									23,874	28,101	31,842
Total segment direct expenses									16,825	19,882	29,112
Total segment selling, general and administrative expenses									1,405	1,101	805
Total net segment profit									5,644	7,118	1,925
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Other, net									2,098	6,214	1,872
Interest expense									(32,183)	(30,644)	(29,066)
Corporate [Member]
Segment Reporting Information [Line Items]
Unallocated selling, general and administrative costs									$ (34,071)	$ (25,610)	$ (28,651)