Net Income Per Common Share - Additional Information (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Feb. 17, 2015	Dec. 31, 2014	[1]
Earnings Per Share [Abstract]
Stock dividend declared	10.00%		10.00%		10.00%
Treasury shares, shares	9,095,585	8,233,645	9,095,585	8,233,645		8,606,489
Antidilutive securities excluded from computation of diluted net income per share, shares	484	2,611	484	2,611

[1] Derived from audited consolidated financial statements.