Summary of Significant Accounting Policies - Earnings per Share (Details) - shares |
3 Months Ended | |
|---|---|---|
Apr. 30, 2018 |
Apr. 30, 2017 |
|
| Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] | ||
| Weighted average common shares outstanding - Basic (in shares) | 31,540,684 | 30,972,312 |
| Weighted average common shares outstanding - Diluted (in shares) | 32,452,864 | 30,972,312 |
| Weighted average number of stock options and restricted stock units not included in the calculation of the dilutive effect of stock options and restricted stock units (in shares) | 305,313 | 944,423 |
| Stock Option [Member] | ||
| Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] | ||
| Dilutive effect of stock options, RSUs and PSUs (in shares) | 912,180 | 0 |