Segment Information - Schedule of Net Revenue Attributable to Insurance, Medicare, Medicaid, and Self-Pay as Percentage of Net Air Medical Revenues (Detail) - Air Medical [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Insurance [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	72.00%	72.00%	72.00%	71.00%
Medicare [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	19.00%	18.00%	20.00%	18.00%
Medicaid [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	8.00%	8.00%	8.00%	9.00%
Self Pay [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	1.00%	2.00%	0.00%	2.00%