Earnings Per Share - Summary of Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share Basic [Abstract]
Net income, as reported	$ 17,443	$ 9,699	$ 7,644	$ 8,851	$ 9,226	$ 7,121	$ 3,445	$ 9,561	$ 43,637	$ 29,353	$ 24,181
Less allocated income to participating securities									142	22	14
Net income available to common shareholders - basic									43,495	29,331	24,167
Basic weighted average common shares									18,373,033	18,166,261	18,249,583
Basic earnings per share	$ 0.94	$ 0.53	$ 0.42	$ 0.48	$ 0.51	$ 0.39	$ 0.19	$ 0.53	$ 2.37	$ 1.62	$ 1.32
Net income available to common shareholders - diluted	$ 17,364	$ 9,673	$ 7,618	$ 8,836	$ 9,216	$ 7,116	$ 3,443	$ 9,556	$ 43,495	$ 29,331	$ 24,167
Weighted average common shares									18,373,033	18,166,261	18,249,583
Stock options and performance shares									375,776	408,930	443,128
Diluted weighted average common shares									18,748,809	18,575,191	18,692,711
Diluted earnings per common share	$ 0.92	$ 0.52	$ 0.41	$ 0.47	$ 0.50	$ 0.38	$ 0.19	$ 0.52	$ 2.32	$ 1.58	$ 1.29