Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value Disclosures [Abstract]
Hedge derivative expiration period	1 month
Proceeds from the sales and maturities of securities available-for-sale	$ 56,800,000	$ 13,300,000
Net unrealized gains on corporate debt trading securities	100,000	100,000
Net realized gains or losses	$ 0	$ 0