Goodwill and Other Intangible Assets, Net of Accumulated Amortization - Additional Information (Detail) - USD ($)	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Additional goodwill recognized	$ 0			$ 64,291,000
Measurement period adjustments	(2,542,000)			$ 395,000
Impairment of goodwill		$ 0
Intangible amortization expense	$ 1,500,000		$ 1,300,000