Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 332	$ 327
Estimated intangible asset amortization expense next twelve months	1,300
Estimated intangible asset amortization expense 2019	1,300
Estimated intangible asset amortization expense 2020	1,200
Estimated intangible asset amortization expense 2021	1,200
Estimated intangible asset amortization expense 2022	1,200
Estimated intangible asset amortization expense 2023	$ 1,200