Goodwill and Other Intangible Assets - Narrative (Detail) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017 USD ($) Reporting_Unit	Dec. 31, 2015 USD ($) Reporting_Unit	Dec. 31, 2017 USD ($) Reporting_Unit	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) Reporting_Unit
Goodwill and Intangible Assets Disclosure [Abstract]
Number of reporting units impacted by impairment charge | Reporting_Unit	2	2	2		2
Amortization of intangible assets			$ 32,205	$ 31,685	$ 34,848
Intangible asset impairment charges	$ 1,100	$ 12,100	$ 1,100		$ 12,100