Summary of Significant Accounting Policies - Schedule of Provisions for Contractual Discounts and Estimated Uncompensated Care Applied to Air Medical Revenues Expressed as Percentage of Total Independent Provider Model Billings (Detail) - Air Medical [Member] |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Provisions For Contractual Discounts And Estimated Uncompensated Care [Line Items] | |||
| Provision for contractual discounts | 67.00% | 65.00% | 72.00% |
| Provision for uncompensated care | 6.00% | 8.00% | 2.00% |