Treasury Stock - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Oct. 25, 2016
Equity [Abstract]
Share repurchase program, new limit amount			$ 25,000,000
Shares repurchased under the program	0
Shares repurchased	1,258,250	1,258,250
Shares repurchased, value	$ 22,400,000
Shares repurchased, average price	$ 17.78