Stock-based Compensation Plans - Additional Information 3 (Detail) - USD ($) $ in Thousands, shares in Millions |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2017 |
Jun. 30, 2016 |
Jun. 30, 2017 |
Jun. 30, 2016 |
Dec. 31, 2016 |
|
| Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] | |||||
| Deferred compensation plan vesting period | 3 years | ||||
| Deferred compensation plan | $ 14,466 | $ (25,746) | $ 27,635 | $ (41,802) | |
| Shares held in rabbi trust total | 2.9 | 2.9 | 2.7 | ||
| Vested shares held in rabbi trust | 2.2 | 2.2 | 2.3 | ||