Reconcilements Between Statutory Federal Income Tax Rate And Effective Tax Rate (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Reconcilements Between Statutory Federal Income Tax Rate and Effective Tax Rate [Line Items]
Income tax expense at federal statutory rate	$ 23,445	$ 19,110	$ 17,481
Increase (decrease) resulting from:
Tax exempt income, net	(3,185)	(2,927)	(2,945)
Bank-owned life insurance	(875)	(916)	(923)
State income taxes, net of federal income tax benefits	2,879	2,424	2,187
Other, net	299	354	45
Total income tax expense (benefit) and rate	$ 22,563	$ 18,045	$ 15,845
Income tax expense at federal statutory rate	35.00%	35.00%	35.00%
Increase (decrease) resulting from:
Tax exempt income, net	(4.70%)	(5.40%)	(5.90%)
Bank-owned life insurance	(1.30%)	(1.70%)	(1.90%)
State income taxes, net of federal income tax benefits	4.30%	4.40%	4.40%
Other, net	0.40%	0.70%	0.10%
Total income tax expense (benefit) and rate	33.70%	33.00%	31.70%