Goodwill and Intangible Assets - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill	$ 31,343,000		$ 31,343,000		$ 9,676,000
Impairment of goodwill			0		$ 0
Amortization expense for intangible assets	$ 900,000	$ 300,000	$ 2,400,000	$ 900,000