Annual report pursuant to Section 13 and 15(d)

Stock-based Expense and Employee Benefits - Additional Information (Detail)

v3.19.3
Stock-based Expense and Employee Benefits - Additional Information (Detail) - USD ($)
$ in Millions
1 Months Ended 12 Months Ended 23 Months Ended 36 Months Ended 58 Months Ended
Jan. 31, 2014
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2018
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Unrecognized compensation cost   $ 73.8       $ 73.8 $ 73.8
Unrecognized non-vested stock awards recognition period   1 year 10 months 24 days          
Aggregate intrinsic value of stock options   $ 23.0 $ 25.1 $ 11.3      
Contributions to employee benefit plans   $ 4.2 $ 2.9 $ 2.4      
Options granted in period (in shares)   0 0 0      
Stock Option              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Award vesting period (in years) 4 years           3 years
Vesting percentage 75.00%            
Percentage of stock options to be vested during remaining period 25.00%            
Expiration period from grant date (in years)   10 years          
Time Based Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Award vesting period (in years) 4 years       3 years 3 years  
Market Based Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Award vesting period (in years)           1 year  
Market Based Restricted Stock | Minimum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Requisite service period (in months)   1 year 6 months 1 year 3 months        
Market Based Restricted Stock | Maximum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Requisite service period (in months)   2 years 6 months 1 year 9 months        
Common Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock options granted (in shares)   27,634,259 27,634,259     27,634,259 27,634,259
Board Plan | Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Award vesting period (in years)   1 year          
Options granted prior to February 2014 | Stock Option              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Award vesting period (in years) 3 years 9 months