Fair Value Measurements Fair Value Measurements - Reconciliation of Contingent Consideration Measured at Fair Value (Detail) - Fair Value, Measurements, Recurring [Member] - Contingent Consideration Liability [Member] - USD ($) |
3 Months Ended | 9 Months Ended |
|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2017 |
|
| Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | ||
| Balances, beginning of period | $ 21,502,000 | $ 0 |
| Purchase | 0 | 21,284,000 |
| Total loss included in other income, net | 3,000 | 221,000 |
| Settlement | 0 | 0 |
| Balances, end of period | $ 21,505,000 | $ 21,505,000 |