Financial Instruments and Fair Value Measurements - Foreign Currency Contracts Activity (Parenthetical) (Detail) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
|
Sep. 30, 2017
USD ($)
|
Sep. 30, 2016
USD ($)
|
Sep. 30, 2017
USD ($)
Contracts
|
Sep. 30, 2016
USD ($)
Contracts
|
|
| Derivative Instruments And Hedging Activities Disclosure [Abstract] | ||||
| Number of forward and option contracts exercised | Contracts | 33 | 41 | ||
| Gains (losses) from forward and option contracts exercised | $ | $ 1.6 | $ (3.1) | $ 10.5 | $ (1.2) |