Additional Information on Non-vested Restricted Stock (Detail) - Restricted Stock Awards $ in Millions |
12 Months Ended |
---|---|
Dec. 31, 2016
USD ($)
| |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Aggregate intrinsic value | $ 34.0 |
Weighted-average remaining vesting period | 1 year 9 months 18 days |
Unrecognized compensation cost | $ 21.3 |