Goodwill and Other Identifiable Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amortization and Impairment
Accumulated goodwill impairment losses		$ 200,500,000		$ 200,500,000
Amortization		$ 97,700,000	$ 96,400,000	$ 68,100,000
Impairment charges, related to trade names	$ 13,300,000				$ 0