Stock Options and Restricted Stock - Stock Options Outstanding (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares outstanding, Beginning balance	576,248	832,548	919,348
Shares, Granted	0	0	0
Shares, Exercised	(294,165)	(256,300)	(86,800)
Shares Canceled, forfeited, or expired	0	0	0
Shares outstanding, Ending balance	282,083	576,248	832,548	919,348
Shares exercisable, Ending balance	282,083	557,448	779,948
Weighted- Average Exercise Price, Beginning balance	$ 11.12	$ 10.51	$ 10.37
Weighted- Average Exercise Price, Granted	$ 0	$ 0	$ 0
Weighted- Average Exercise Price, Exercised	$ 9.09	$ 9.00	$ 9.00
Weighted- Average Exercise Price, Canceled, forfeited, or expired	$ 0	$ 0	$ 0
Weighted- Average Exercise Price, Ending balance	$ 11.30	$ 11.12	$ 10.51	$ 10.37
Weighted- Average Exercise Price, Exercisable Ending balance	$ 11.30	$ 10.91	$ 10.08
Weighted- Average Remaining Contractual Life (in years)	3 years 7 months 6 days	3 years 9 months 18 days	4 years 7 months 6 days	5 years 6 months 5 days
Weighted- Average Remaining Contractual Life (in years), Exercisable	3 years 7 months 6 days	3 years 8 months 12 days	4 years 4 months 24 days
Weighted- Average Remaining Contractual Life (in years)	3 years 7 months 6 days	3 years 9 months 18 days	4 years 7 months 6 days	5 years 6 months 5 days