Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan [Abstract]
Percentage of employees contributions maximum	50.00%
Percentage of company matches of employees contributions maximum	3.00%
Employee vesting period	2 years
Employer contributions for benefit plans	$ 70	$ 60	$ 53