Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill and intangible assets with indefinite lives	$ 62,675	$ 63,059
Amortization expense associated with identifiable intangible assets	400	400	$ 700
Estimated total amortization expense 2019	400
Estimated total amortization expense 2020	400
Estimated total amortization expense 2021	400
Estimated total amortization expense 2022	400
Estimated total amortization expense 2023	300
Indefinite-lived Intangible Assets [Member]
Goodwill [Line Items]
Goodwill and intangible assets with indefinite lives	$ 59,700	$ 59,700