Stock Repurchase Program - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2008	Dec. 31, 2007
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program					$ 23,100,000	$ 5,000,000
Stock repurchase program expiration date			Sep. 23, 2016
Repurchase of common stock	0	0	0	0
Prior Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program expiration date			Sep. 22, 2017