Goodwill and Other Intangible Assets - Components of Goodwill and Other Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill	$ 381,902	$ 373,117	$ 322,939	$ 320,761
Other intangible assets (net of accumulated amortization)	7,314	8,907
Goodwill and other intangible assets, Total	$ 389,216	$ 382,024