Calculation of Net Income per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income	$ 44,422	$ 36,554	$ 34,102
Less: Dividends - preferred stock	0	0	0
Net income available to common stockholders	$ 44,422	$ 36,554	$ 34,102
Basic:
Basic weighted average EPS shares	24,961	24,573	24,083
Basic net income per share	$ 1.78	$ 1.49	$ 1.42
Basic net income per common share	$ 1.78	$ 1.49	$ 1.42
Diluted:
Basic weighted average EPS shares	24,961	24,573	24,083
Dilutive common stock equivalents	114	84	66
Dilutive EPS shares	25,075	24,657	24,149
Diluted net income per share	$ 1.77	$ 1.48	$ 1.41
Diluted net income per common share	$ 1.77	$ 1.48	$ 1.41
Anti-dilutive shares	164	421	621