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 | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
|
| Provisions For Contractual Discounts And Estimated Uncompensated Care [Line Items] | ||||
| Provision for contractual discounts | 65.00% | 65.00% | 66.00% | 67.00% |
| Provision for uncompensated care | 6.00% | 9.00% | 7.00% | 6.00% |