Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Domestic Plan
Defined Contribution Plan Disclosure [Line Items]
Employer contributions to plan	$ 11.6	$ 11.4	$ 10.9
Foreign Plan
Defined Contribution Plan Disclosure [Line Items]
Employer contributions to plan	$ 6.4	$ 6.3	$ 6.1