Goodwill and Acquired Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Goodwill acquired		$ 35,000,000
Intangible assets acquired	$ 10,668,000	10,668,000
Gross carrying amount of goodwill	34,972,000	34,972,000
Goodwill impairments	0	0	$ 0
Amortization of acquired intangibles	$ 1,408,000	$ 1,269,000	$ 0
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	7 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	10 years