Segment Information - Schedule of Provisions for Contractual Discounts and Estimated Uncompensated Care as a Percentage of Gross Segment Billings (Detail) - Air Medical [Member]	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Provisions For Contractual Discounts And Estimated Uncompensated Care [Line Items]
Provision for contractual discounts	67.00%	69.00%
Provision for uncompensated care	11.00%	6.00%