Quarterly report pursuant to Section 13 or 15(d)

Stock-based Expense - Schedule of Stock-based Expense (Details)

v3.19.1
Stock-based Expense - Schedule of Stock-based Expense (Details)
3 Months Ended
Mar. 31, 2019
$ / shares
shares
Performance-Based Restricted Stock  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted shares of restricted stock (in shares) 468,132
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) 11,300
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) | $ / shares $ 60.84
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) 105,733
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) | $ / shares $ 60.89
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) 11,300
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) | $ / shares $ 66.92
Performance-Based Restricted Stock | Vesting condition 4  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted shares of restricted stock (in shares) 105,733
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) | $ / shares $ 66.98
Performance-Based Restricted Stock | Vesting condition 5  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted shares of restricted stock (in shares) 11,300
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) | $ / shares $ 73.01
Performance-Based Restricted Stock | Vesting condition 6  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted shares of restricted stock (in shares) 105,733
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) | $ / shares $ 73.07
Performance-Based Restricted Stock | Vesting Condition 7  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted shares of restricted stock (in shares) 11,300
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) | $ / shares $ 85.17
Performance-Based Restricted Stock | Vesting Condition 8  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted shares of restricted stock (in shares) 105,733
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) | $ / shares $ 85.24
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) 637,887
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) 22,675
2010 Equity Incentive Plan | Restricted Stock | Vesting condition 3  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Granted shares of restricted stock (in shares) 1,380
Vesting period (in years) 1 year