Valuation Accounts - Schedule of Allowance for Contractual Discounts and Estimated Uncompensated Care as a Percentage of Gross Segment Accounts Receivable (Detail) - Air Medical [Member] - Trade Accounts Receivable [Member]	Mar. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for Contractual Discounts	50.00%	51.00%
Allowance for Uncompensated Care	22.00%	22.00%