Earnings Per Share - Additional Information (Detail) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||||
|---|---|---|---|---|---|---|
Sep. 30, 2015 |
Sep. 30, 2014 |
Sep. 30, 2015 |
Sep. 30, 2014 |
Feb. 28, 2015 |
Dec. 31, 2014 |
|
| Earnings Per Share [Abstract] | ||||||
| Antidilutive securities excluded from computation of earnings per share amount | 400,000 | 500,000 | 0 | 500,000 | ||
| Additional authorized repurchase amount | $ 100.0 | $ 42.4 | ||||
| Number of shares repurchased | 744,081 | 283,283 | 1,525,222 | 1,074,574 | ||
| Repurchase of common stock, value | $ 25.9 | $ 11.4 | $ 57.4 | $ 43.0 | ||
| Treasury stock reissued, shares | 369,591 | 225,783 | ||||