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Employee Benefit Plans - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]      
Defined contribution pension plans $ 3.1 $ 2.5 $ 2.7
CMRT      
Compensation And Retirement Disclosure [Abstract]      
Percentage of assets valued using observable inputs from level one or level two (or assets not subject to classification in the fair value hierarchy)   93.00%  
CMRT | United States      
Compensation And Retirement Disclosure [Abstract]      
Defined benefit plan assets 6.00%    
Equity Securities | United States      
Compensation And Retirement Disclosure [Abstract]      
Long-term return on plan assets 9.00%    
Plan asset target allocation 40.00%    
Fixed Income | United States      
Compensation And Retirement Disclosure [Abstract]      
Long-term return on plan assets 5.00%    
Plan asset target allocation 45.00%    
Funds | United States      
Compensation And Retirement Disclosure [Abstract]      
Defined benefit plan assets 29.00%    
Multi-asset Strategies and CMRT | United States      
Compensation And Retirement Disclosure [Abstract]      
Long-term return on plan assets 3.00%    
Defined Benefit Pension Plans      
Compensation And Retirement Disclosure [Abstract]      
Expected contributions to Defined Benefit Plans in Next Fiscal Year $ 1.5    
Actuarial losses expected to be recognized as a component of net period cost in next fiscal year $ 1.6    
Weighted-average rate determining the actuarial present value of benefit obligation 3.90% 3.40%  
Long-term return on plan assets 7.20% 6.90% 7.00%
Defined Benefit Pension Plans | CMRT      
Compensation And Retirement Disclosure [Abstract]      
Long-term return on plan assets 7.50% 7.50% 7.50%