Goodwill and Other Intangible Assets - Estimated Other Intangible Assets Amortization Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense for other intangible assets total	$ 51,993	$ 40,870	$ 34,878
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2018	83,564
2019	83,137
2020	82,199
2021	82,044
2022	82,137
Estimated other intangible assets amortization expense	$ 413,081