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, 2017	Mar. 31, 2016
Provisions For Contractual Discounts And Estimated Uncompensated Care [Line Items]
Gross Air Medical segment billings	100.00%	100.00%
Provision for contractual discounts	70.00%	71.00%
Provision for uncompensated care	4.00%	3.00%