Business Segments and Geographic Areas - Summary of Gains on Disposition of Property and Equipment and Other Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting, Asset Reconciling Item [Line Items]
Expenditures for long-lived assets	$ 56,575	$ 157,705	$ 102,590
Depreciation and amortization	71,618	50,848	42,848
Total assets	1,430,332	1,376,080
Reportable Operating Segments [Member] \| Oil and Gas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Expenditures for long-lived assets	32,501	119,235	62,934
Depreciation and amortization	42,709	29,635	26,653
Total assets	704,472	726,008
Reportable Operating Segments [Member] \| Air Medical [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Expenditures for long-lived assets	22,685	37,317	37,728
Depreciation and amortization	18,177	13,067	11,395
Total assets	329,484	336,510
Reportable Operating Segments [Member] \| Technical Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Depreciation and amortization	518	493	172
Total assets	7,345	7,842
Corporate [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Expenditures for long-lived assets	1,389	1,153	1,928
Depreciation and amortization	10,214	7,653	$ 4,628
Total assets	$ 389,031	$ 305,720