Shares Repurchased - Additional Information (Detail) - Three-Year Share Repurchase Program [Member] - USD ($)		3 Months Ended		9 Months Ended
	Apr. 27, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Oct. 29, 2014
Class of Stock [Line Items]
Common stock purchase authorized amount						$ 100,000,000
Share repurchase program, increase in authorized amount	$ 60,000,000
Share repurchase program, extended term date	Apr. 27, 2019
Repurchased common stock, shares		47,317	337,824	401,813	3,753,147
Repurchased common stock, value		$ 484,000	$ 3,462,000	$ 4,178,000	$ 39,116,000
Dollar amount remaining available for future share repurchases		$ 92,327,000		$ 92,327,000