Goodwill and Other Intangible Assets, Net - Additional Information (Detail)		12 Months Ended
	Nov. 01, 2017 USD ($) Reporting_Unit	Dec. 31, 2017 USD ($) Reporting_Unit	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Finite-Lived Intangible Assets [Line Items]
Number of reporting units | Reporting_Unit	5	5
Goodwill, Impairment Loss	$ 0
Intangible assets amortization period		7 years 1 month 6 days
2018		$ 17,100,000
2019		12,900,000
2020		11,600,000
2021		10,300,000
2022		$ 8,500,000
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets amortization period		2 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets amortization period		15 years
Client Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 17,800,000	$ 16,700,000	$ 14,700,000
Intangible assets amortization period		7 years
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets amortization period		8 years 3 months 18 days
Other Intangible Assets [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets amortization period		2 years
Other Intangible Assets [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets amortization period		12 years