Goodwill and Other Intangible Assets Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 637,486,000		$ 637,486,000		$ 433,374,000
Total other intangible assets, net	877,945,000		877,945,000		$ 347,212,000
Amortization expense of intangible assets	10,403,000	$ 6,344,000	22,586,000	$ 18,792,000
Estimated Future Amortization Expense by Fiscal Year [Abstract]
Remainder of 2016	10,500,000		10,500,000
2017	40,500,000		40,500,000
2018	35,500,000		35,500,000
2019	32,700,000		32,700,000
2020	27,700,000		27,700,000
2021	25,300,000		25,300,000
After 2021	$ 264,800,000		$ 264,800,000