Earnings Per Share - Additional Information (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Earnings Per Share [Line Items]
Stock options, outstanding	1,252,356	1,259,317	1,252,356	1,259,317	1,225,117
Stock options, weighted average exercise price	$ 10.47	$ 7.61	$ 10.47	$ 7.61	$ 8.31
Common stock excluded from calculation of diluted earnings per share	163,459	263,475	170,891	289,475