Share Repurchase Program - Additional Information (Detail) - Share Repurchase Program [Member] - USD ($)	1 Months Ended		9 Months Ended
	Sep. 30, 2017	Jan. 31, 2016	Sep. 30, 2017	Oct. 31, 2016
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program authorized	$ 100,000,000	$ 25,000,000	$ 100,000,000
Shares repurchase program period		2 years
Commencement date	2017-10
Shares repurchase program additional authorized amount				$ 50,000,000
Total shares repurchased			191,394
Cost of common stock shares repurchased			$ 36,400,000