Summary of Significant Accounting Policies - Provisions for Contractual Discounts and Uncompensated Care Applied to Air Medical Trade Receivables Expressed as Percentage of Total Segment Accounts Receivable (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] | |||
| Allowance for contractual discounts | 67.00% | 65.00% | 72.00% |
| Trade Accounts Receivable [Member] | |||
| Provisions For Contractual Discounts And Estimated Uncompensated Care [Line Items] | |||
| Allowance for contractual discounts | 56.00% | 56.00% | |
| Allowance for uncompensated care | 23.00% | 23.00% | |