Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expense	$ 900,000	$ 900,000	$ 800,000
Subsequent impairment of the underlying assets	0
Expected annual amortization expense for 2017	900,000
Expected annual amortization expense for 2018	900,000
Expected annual amortization expense for 2019	900,000
Expected annual amortization expense for 2020	$ 200,000