Quarterly report pursuant to Section 13 or 15(d)

Stock-based Expense (Details)

v3.8.0.1
Stock-based Expense (Details) - $ / shares
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2017
Performance-Based Restricted Stock    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares)   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) 0 178,480
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) 0 178,480
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]    
Granted shares of restricted stock (in shares) 0 178,481
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) 95,601 1,215,940
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) 0 49,563
Vesting period (in years)   1 year