Earnings per Share - Schedule of Basic and Diluted Earnings per Common Share and the Average Number of Common Shares Outstanding (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Earnings Per Share Basic And Diluted [Line Items] | |||
| Basic | $ 1.81 | $ 3.22 | $ 1.77 |
| Diluted | $ 1.80 | $ 3.22 | $ 1.77 |
| Net earnings | $ 59.1 | $ 104.3 | $ 57.4 |
| Weighted average number of common shares outstanding | 32.6 | 32.4 | 32.4 |
| Dilutive awards | 0.2 | 0.0 | 0.0 |
| Diluted weighted average number of common shares outstanding | 32.8 | 32.4 | 32.4 |
| Total weighted average number of anti-dilutive share-based awards | 0.4 | 0.0 | 0.0 |
| Restricted stock units | |||
| Earnings Per Share Basic And Diluted [Line Items] | |||
| Total weighted average number of anti-dilutive share-based awards | 0.2 | 0.0 | 0.0 |
| Stock options | |||
| Earnings Per Share Basic And Diluted [Line Items] | |||
| Total weighted average number of anti-dilutive share-based awards | 0.2 | 0.0 | 0.0 |