XML 106 R70.htm IDEA: XBRL DOCUMENT v3.10.0.1
Stockholders' Equity (Details Textual)
 1 Months Ended 3 Months Ended 12 Months Ended
Nov. 06, 2016
USD ($)
Oct. 25, 2016
shares
Oct. 29, 2014
$ / shares
shares
Feb. 28, 2017
USD ($)
$ / shares
shares
May 31, 2017
USD ($)
$ / shares
shares
Nov. 30, 2016
USD ($)
shares
May 31, 2018
USD ($)
working_hour
Employees
$ / shares
shares
May 31, 2017
USD ($)
$ / shares
shares
May 31, 2016
USD ($)
$ / shares
shares
May 31, 2015
shares
Other Ownership Interests [Line Items]                    
Authorized capital stock (shares) | shares     80,000,000              
Shares of common stock (shares) | shares     75,000,000   75,000,000   75,000,000 75,000,000    
Common stock, par value (usd per share) | $ / shares     $ 0.01 $ 0.01 $ 0.01   $ 0.01 $ 0.01    
Preferred stock, shares authorized (shares) | shares     5,000,000   5,000,000   5,000,000 5,000,000    
Preferred stock, par value (usd per share) | $ / shares     $ 0.01   $ 0.01   $ 0.01 $ 0.01    
Common stock, votes per share     1              
Subsequent grants for directors vesting             33.33%      
Subsequent grants for directors vesting period             3 years      
Option grants in the period, weighted average grant date fair value (usd per share) | $ / shares             $ 4.95 $ 4.70 $ 4.16  
Risk free interest rate             2.08% 1.30% 1.48%  
Expected volatility rate             30.00% 31.00% 31.00%  
Expected term             4 years 8 months 20 days 4 years 9 months 20 days 4 years 9 months 21 days  
Dividends | $             $ 0 $ 0 $ 0  
The total intrinsic value of options exercised | $             700,000 2,800,000 100,000  
Compensation not yet recognized | $             3,900,000      
Proceeds from stock options exercised | $             2,000,000 9,900,000 1,300,000  
Tax benefit | $             $ 1,800,000 $ 2,200,000 $ 1,000,000  
Grants in the period, weighted average grant date fair value (usd per share) | $ / shares               $ 16.54 $ 15.21  
Average price of share issued | $ / shares         $ 11.00   $ 14.03 $ 11.00 $ 10.67  
Common stock repurchased | $               $ 13,557,000    
Repurchase of common stock | $         $ 5,700,000   $ 0 13,557,000 $ 0  
Treasury stock retirement | $               $ 0    
Common Stock                    
Other Ownership Interests [Line Items]                    
Maximum number of shares to be offered under the Stock Purchase Plan | shares             89,943 129,185 137,957  
Common stock repurchased (shares) | shares               370,000    
Common stock repurchased | $               $ (3,000)    
Treasury stock retirement (shares) | shares       642,305       (642,305)    
Treasury stock retirement | $       $ 9,900,000       $ (2,000)    
Additional paid in capital                    
Other Ownership Interests [Line Items]                    
Treasury stock retirement | $       $ 9,900,000       (9,942,000)    
Common Stock                    
Other Ownership Interests [Line Items]                    
Share repurchases, authorized amount | $ $ 25,000,000                  
Share repurchase program period 24 months                  
Common stock repurchased (shares) | shares           500,000        
Common stock repurchased | $           $ 7,800,000        
Share repurchases | shares         370,000          
Share repurchases, remaining shares | $             $ 11,400,000      
Employee Stock Option                    
Other Ownership Interests [Line Items]                    
Percentage of grants to employees vesting             25.00%      
Option grants to employees vesting period             4 years      
Period of recognition for costs not yet recognized             4 years      
Tax benefit | $             $ 0 $ 0 $ 100,000  
Restricted Stock Units                    
Other Ownership Interests [Line Items]                    
Period of recognition for costs not yet recognized             3 years      
Vesting percentage (as percent)             25.00%      
Vesting period             1 year      
Grants in the period, weighted average grant date fair value (usd per share) | $ / shares             $ 16.60      
Employee service, compensation cost not yet recognized | $             $ 5,100,000      
Nonvested compensation, weighted average grant date fair value (usd per share) | $ / shares         $ 15.55   $ 16.23 $ 15.55    
Nonvested compensation (shares) | shares         439,297   474,502 439,297    
Performance Share and Restricted Stock Unit Awards                    
Other Ownership Interests [Line Items]                    
Total fair value of restricted stock awards vesting | $             $ 2,700,000 $ 2,900,000 $ 2,500,000  
Performance Shares                    
Other Ownership Interests [Line Items]                    
Employee service, compensation cost not yet recognized | $             $ 3,900,000      
Nonvested compensation, weighted average grant date fair value (usd per share) | $ / shares         $ 22.61   $ 23.83 $ 22.61 $ 18.07  
Performance period             3 years      
Nonvested compensation (shares) | shares             500,000      
Weighted average remaining contractual term             2 years      
Employee Stock Option                    
Other Ownership Interests [Line Items]                    
Period of recognition for costs not yet recognized             3 years      
2004 Stock and Incentive Award Plan                    
Other Ownership Interests [Line Items]                    
Total number of common stock reserved for issuance (shares) | shares             7,000,000      
Total number of common stock available to be issued (shares) | shares             1,800,000      
Options exercisable period             10 years      
Incentive award plan to increase the minimum number of shares (shares) | shares   250,000                
2004 Stock and Incentive Award Plan | Maximum                    
Other Ownership Interests [Line Items]                    
Total number of common stock available to be issued (shares) | shares             800,000      
Stock Purchase Plan                    
Other Ownership Interests [Line Items]                    
Total number of common stock available to be issued (shares) | shares             1,200,000.0      
Maximum number of shares to be offered | shares             2,500,000      
Share purchase periods | Employees             2      
Duration of purchase of shares             6 months      
Employee eligible in participating in offering period             6 months      
Working schedule of employee to participate in offering period             20 or more hours per week and more than five months in a calendar year      
Number of working hours to be eligible (working hour) | working_hour             20      
Number of working months to be eligible             5 months      
Employees ownership threshold             5.00%      
Percentage of fair market value of a share of common stock on the first day of the offering period             85.00%      
Percentage of fair market value of a share of common stock on the last day of the offering period             85.00%      
Number of additional shares reserved for issuance (shares) | shares               500,000   800,000
Maximum number of shares to be offered under the Stock Purchase Plan | shares             89,943 129,185 137,957