Segment Information - Schedule of Net Revenue Attributable to Insurance, Medicare, Medicaid, and Self-Pay as Percentage of Net Air Medical Revenues (Detail) - Product Concentration Risk [Member] - Sales Revenue Net [Member] - Air Medical [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	42.00%	40.00%	40.00%	38.00%
Insurance [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	67.00%	72.00%	67.00%	72.00%
Medicare [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	23.00%	19.00%	23.00%	20.00%
Medicaid [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	9.00%	8.00%	8.00%	8.00%
Self-Pay [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	1.00%	1.00%	2.00%