Stock-based Compensation - Summary of Stock Option Activity (Detail)	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Shares, Beginning Balance | shares	162,824
Number of Shares, Granted | shares	0
Number of Shares, Exercised | shares	(4,675)
Number of Shares, Forfeited | shares	0
Number of Shares, Ending Balance | shares	158,149
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Beginning Balance (in $ per share)	$ 18.79
Weighted Average Exercise Price, Granted (in $ per share)	0.00
Weighted Average Exercise Price, Exercised (in $ per share)	15.27
Weighted Average Exercise Price, Forfeited (in $ per share)	0.00
Weighted Average Exercise Price, Ending Balance (in $ per share)	$ 18.89