Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.2
Stock-based Expense - Schedule of Stock-based Expense (Details) - $ / shares
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2019
Restricted Stock | Vesting Condition 8    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares)   11,300
Restricted Stock | Vesting Condition 9    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares)   105,733
Restricted Stock | Vesting Condition 10    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares)   3,184
Restricted Stock | Vesting Condition 11    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares)   3,184
Restricted Stock | Vesting Condition 12    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares)   3,198
Performance-Based Restricted Stock    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 12,750 480,882
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 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)   $ 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) 0 105,733
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)   $ 69.50
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 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)   $ 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) 0 105,733
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)   $ 77.84
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) 0 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)   $ 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) 0 105,733
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)   $ 88.96
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) 3,184 3,184
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)   $ 78.44
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) 0  
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)   $ 85.17
Performance-Based Restricted Stock | Vesting Condition 9    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 0  
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)   $ 100.08
Performance-Based Restricted Stock | Vesting Condition 10    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 3,184  
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)   $ 87.85
Performance-Based Restricted Stock | Vesting Condition 11    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 3,184  
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)   $ 100.40
Performance-Based Restricted Stock | Vesting Condition 12    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted shares of restricted stock (in shares) 3,198  
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)   $ 112.95
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) 99,383 737,270
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 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) 25,515 26,895
Vesting period (in years)   1 year