Income Taxes (Reconcilements Between Statutory Federal Income Tax Rate And Effective Tax Rate) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax expense at federal statutory rate									$ 23,584	$ 19,523	$ 23,445
Increase (decrease) resulting from:
Tax exempt income, net									(3,457)	(3,468)	(3,185)
Bank-owned life insurance									(900)	(855)	(875)
State income taxes, net of federal income tax benefits									2,687	2,182	2,879
Other, net									113	200	299
Total income tax expense (benefit)	$ 6,372	$ 5,175	$ 5,014	$ 5,466	$ 4,086	$ 5,428	$ 2,722	$ 5,346	$ 22,027	$ 17,582	$ 22,563
Income tax expense at federal statutory rate									35.00%	35.00%	35.00%
Increase (decrease) resulting from:
Tax exempt income, net									(5.10%)	(6.20%)	(4.70%)
Bank-owned life insurance									(1.30%)	(1.50%)	(1.30%)
State income taxes, net of federal income tax benefits									4.00%	3.90%	4.30%
Other, net									0.10%	0.40%	0.40%
Total income tax expense (benefit) and rate									32.70%	31.60%	33.70%