Segment Information - Schedule of Financial Information Concerning Reportable Operating Segments (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Total operating revenues, net		$ 167,136	$ 198,547	$ 331,152	$ 402,744
Total direct expenses		152,417	168,828	304,971	338,035
Total segment selling, general and administrative expenses		11,778	12,047	23,451	23,284
Total		7,163	17,632	6,593	41,324
Interest expense		(7,540)	(7,155)	(15,073)	(14,325)
Earnings (loss) before income taxes		117	11,044	(7,371)	28,028
Reportable Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net		167,136	198,547	331,152	402,744
Total direct expenses	[1]	152,493	168,934	305,047	338,209
Total segment selling, general and administrative expenses		4,520	4,010	8,866	7,912
Total segment expenses		157,013	172,944	313,913	346,121
Total		10,123	25,603	17,239	56,623
Reportable Operating Segments [Member] | Air Medical [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net		75,547	81,642	145,607	154,027
Total direct expenses	[1]	58,997	63,576	116,041	123,615
Total segment selling, general and administrative expenses		2,642	2,527	5,237	5,156
Total		13,908	15,539	24,329	25,256
Reportable Operating Segments [Member] | Oil and Gas [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net		83,185	112,839	171,622	233,235
Total direct expenses	[1],[2]	87,400	100,262	179,316	200,593
Total segment selling, general and administrative expenses		1,605	1,275	3,132	2,434
Total		(5,820)	11,302	(10,826)	30,208
Reportable Operating Segments [Member] | Technical Services [Member]
Segment Reporting Information [Line Items]
Total operating revenues, net		8,404	4,066	13,923	15,482
Total direct expenses	[1]	6,096	5,096	9,690	14,001
Total segment selling, general and administrative expenses		273	208	497	322
Total		2,035	(1,238)	3,736	1,159
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Other, net	[3]	4,792	633	5,048	1,102
Interest expense		(7,540)	(7,155)	(15,073)	(14,325)
Unallocated Selling, General and Administrative Expenses [Member]
Segment Reporting Information [Line Items]
Unallocated selling, general and administrative costs	[1]	$ (7,258)	$ (8,037)	$ (14,585)	$ (15,372)

[1] Included in direct expenses and unallocated selling, general and administrative costs are the depreciation and amortization expense amounts below: Depreciation and Amortization Expense Quarter Ended June 30, Six Months Ended June 30, Segment Direct Expense: 2016 2015 2016 2015 Oil and Gas $ 10,024 $ 10,323 $ 19,942 $ 21,603 Air Medical 5,132 4,750 9,387 8,848 Technical Services 157 132 285 260 Total $ 15,313 $ 15,205 $ 29,614 $ 30,711 Unallocated SG&A $ 2,476 $ 3,155 $ 5,147 $ 5,801

[2] Includes Equity in loss of unconsolidated affiliate.

[3] Consists of gains on disposition of property and equipment, and other income.