Share-Based Compensation - Stock Options (Details) $ in Millions |
3 Months Ended | 9 Months Ended | ||
---|---|---|---|---|
Feb. 29, 2016
USD ($)
shares
|
Feb. 28, 2015
USD ($)
|
Feb. 29, 2016
USD ($)
plan
shares
|
Feb. 28, 2015
USD ($)
shares
|
|
Share-based compensation | ||||
Number of employee stock ownership plans (plan) | plan | 2 | |||
Stock Options | ||||
Share-based compensation | ||||
Recognized share-based compensation expense (less than) | $ | $ 0.1 | $ 0.1 | $ 0.1 | $ 0.1 |
Unrecognized compensation costs, net of estimated forfeitures (less than) | $ | $ 0.1 | $ 0.1 | ||
Weighted-average period over which unrecognized compensation cost is expected to be recognized (years) | 1 month | |||
Stock options granted (in shares) | shares | 0 | 0 | ||
2007 Plan | ||||
Share-based compensation | ||||
Number of awards that may be granted (in shares) | shares | 0 | 0 |