Segment Information - Depreciation and Amortization Expense Included in Direct Expenses and Unallocated Selling, General, and Administrative Costs (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reportable operating segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Depreciation and Amortization Expenses	$ 9,326	$ 8,485	$ 28,164	$ 24,721
Reportable operating segments [Member] | Oil And Gas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Depreciation and Amortization Expenses	6,403	6,018	19,707	17,545
Reportable operating segments [Member] | Air Medical [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Depreciation and Amortization Expenses	2,873	2,453	8,376	7,118
Reportable operating segments [Member] | Technical Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Depreciation and Amortization Expenses	50	14	81	58
Unallocated S,G & A [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Depreciation and Amortization Expenses	$ 1,235	$ 270	$ 3,260	$ 815