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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax expense at federal statutory rate									$ 30,776	$ 25,194	$ 23,584
Income tax expense at federal statutory rate									35.00%	35.00%	35.00%
Increase (decrease) resulting from:
Tax exempt income, net									$ (3,929)	$ (3,606)	$ (3,457)
Bank-owned life insurance									(841)	(862)	(900)
State income taxes, net of federal income tax benefits									3,508	2,965	2,687
Federal tax rate change									5,544	0	0
Other, net									(332)	49	113
Total income tax expense (benefit)	$ 11,933	$ 8,229	$ 6,966	$ 7,598	$ 6,879	$ 6,734	$ 5,008	$ 5,119	$ 34,726	$ 23,740	$ 22,027
Increase (decrease) resulting from:
Tax exempt income, net									(4.50%)	(5.00%)	(5.10%)
Bank-owned life insurance									(0.90%)	(1.10%)	(1.30%)
State income taxes, net of federal income tax benefits									4.00%	4.10%	4.00%
Federal tax rate change									6.30%	0.00%	0.00%
Other, net									(0.40%)	0.00%	0.10%
Total income tax expense (benefit) and rate									39.50%	33.00%	32.70%
Tax cut and jobs act
New US federal coproate tax rate, after Tax Cuts and Jobs Act									21.00%