Quarterly report pursuant to Section 13 or 15(d)

Stock-based Expense (Details)

v3.7.0.1
Stock-based Expense (Details) - $ / shares
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2017
Restricted Stock | Vesting condition 3    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 3,136 178,481
Performance-Based Restricted Stock    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 9,404 535,441
Performance-Based Restricted Stock | Vesting condition 1    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 3,134 178,480
Number of consecutive trading days required to calculate average price per share (in days)   20 days
Minimum price per common stock for vesting eligibility (in dollars per share)   $ 38.05
Performance-Based Restricted Stock | Vesting condition 2    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 3,134 178,480
Number of consecutive trading days required to calculate average price per share (in days)   20 days
Minimum price per common stock for vesting eligibility (in dollars per share)   $ 41.09
Performance-Based Restricted Stock | Vesting condition 3    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of consecutive trading days required to calculate average price per share (in days)   20 days
Minimum price per common stock for vesting eligibility (in dollars per share)   $ 45.66
2010 Equity Incentive Plan | Restricted Stock | Vesting condition 1    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 67,437 1,120,339
Vesting period (in years)   3 years
2010 Equity Incentive Plan | Restricted Stock | Vesting condition 2    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 40,103 49,563
Vesting period (in years)   1 year