Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
OPERATING ACTIVITIES
Net income	$ 82,607	$ 75,610	$ 71,947
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	17,862	17,141	13,773
Depreciation, amortization and accretion	9,723	7,340	6,788
Loss on sales of bank premises, OREO and equipment	262	1,072	1,835
Loss on securities	6,930	18,838	7,809
Loans originated for sale	(146,966)	(66,990)	(49,181)
Proceeds from sales of loans	135,577	72,971	48,258
Gain on sales of loans	(2,471)	(952)	(662)
Stock-based compensation	1,908	1,133	1,050
Deferred income tax expense	337	10,907	6,582
Increase in cash surrender value of bank-owned life insurance policies	(5,039)	(5,286)	(4,673)
Contribution to pension plan	0	0	(9,100)
Amortization of net periodic pension costs	3,567	912	1,467
Changes in:
Interest receivable	159	(2,897)	3,594
Other assets	17,264	3,329	4,634
Accrued expenses and other liabilities	7,719	(14,652)	(3,297)
NET CASH PROVIDED BY OPERATING ACTIVITIES	129,439	118,567	100,824
INVESTING ACTIVITIES
Proceeds from maturities and calls of held to maturity securities	15,973	7,635	6,480
Proceeds from sales of securities held to maturity	0	0	2,979
Proceeds from sales of securities available for sale	5,381	24,763	57,294
Proceeds from maturities and calls of securities available for sale	1,991,166	1,462,173	1,331,904
Purchases of securities available for sale	(1,926,898)	(1,417,978)	(1,236,221)
Redemption of bank-owned life insurance policies	0	822	0
Purchases of bank premises and equipment	(5,207)	(8,018)	(3,273)
Proceeds from sales of bank premises and equipment	2,238	24	11
Acquisition of Centra Financial Holdings, Inc., net of cash acquired	0	49,085	0
Proceeds from sales and redemptions of other investment securities	13,345	10,819	4,816
Purchases of other investment securities	(5,665)	(338)	(173)
Net change in loans	(298,474)	29,350	468,106
NET CASH (USED IN) PROVIDED BY INVESTING ACTIVITIES	(208,141)	158,337	631,923
FINANCING ACTIVITIES
Cash dividends paid	(62,333)	(54,344)	(52,257)
Excess tax benefits from stock-based compensation arrangements	35	3,114	459
Acquisition of treasury stock	(12)	(18)	(11)
Proceeds from exercise of stock options	115	542	2,492
Distribution of treasury stock for deferred compensation plan	130	74	520
Repayment of long-term Federal Home Loan Bank borrowings	(55,398)	(60,372)	(385,032)
Redemption of issued trust preferred securities	(5,155)	0	0
Changes in:
Time deposits	(299,803)	(274,652)	(591,732)
Other deposits	237,001	250,380	334,166
Federal funds purchased, securities sold under agreements to repurchase and other short-term borrowings	60,196	32,986	(29,730)
NET CASH USED IN FINANCING ACTIVITIES	(125,224)	(102,290)	(721,125)
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(203,926)	174,614	11,622
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	636,003	461,389	449,767
CASH AND CASH EQUIVALENTS AT END OF YEAR	$ 432,077	$ 636,003	$ 461,389