Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
OPERATING ACTIVITIES
Net income	$ 85,628	$ 82,607	$ 75,610
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	19,267	17,862	17,141
Depreciation, amortization and accretion	11,679	9,723	7,340
Loss on sales of bank premises, OREO and equipment	592	262	1,072
Loss on securities	5,809	6,930	18,838
Loans originated for sale	(135,260)	(146,966)	(66,990)
Proceeds from sales of loans	151,357	135,577	72,971
Gain on sales of loans	(2,571)	(2,471)	(952)
Stock-based compensation	1,786	1,908	1,133
Deferred income tax expense	2,990	337	10,907
Increase in cash surrender value of bank-owned life insurance policies	(6,043)	(5,039)	(5,195)
Amortization of net periodic pension costs	4,094	3,567	912
Changes in:
Interest receivable	(364)	159	(2,897)
Other assets	9,721	17,264	3,329
Accrued expenses and other liabilities	(6,486)	7,719	(14,652)
NET CASH PROVIDED BY OPERATING ACTIVITIES	142,199	129,439	118,567
INVESTING ACTIVITIES
Proceeds from maturities and calls of held to maturity securities	2,479	15,973	7,635
Proceeds from sales of securities available for sale	14,352	5,381	24,763
Proceeds from maturities and calls of securities available for sale	683,913	1,991,166	1,462,173
Purchases of securities available for sale	(845,908)	(1,926,898)	(1,417,978)
Redemption of bank-owned life insurance policies	2,573	0	822
Purchases of bank premises and equipment	(5,995)	(5,207)	(8,018)
Proceeds from sales of bank premises and equipment	203	2,238	24
Acquisition of Centra Financial Holdings, Inc., net of cash acquired	0	0	49,085
Proceeds from sales and redemptions of other investment securities	27,648	13,345	10,819
Purchases of other investment securities	(40,237)	(5,665)	(338)
Net change in loans	(212,137)	(298,474)	29,350
NET CASH (USED IN) PROVIDED BY INVESTING ACTIVITIES	(373,109)	(208,141)	158,337
FINANCING ACTIVITIES
Cash dividends paid	(62,434)	(62,333)	(54,344)
Excess tax benefits from stock-based compensation arrangements	331	35	3,114
Acquisition of treasury stock	(93)	(12)	(18)
Proceeds from exercise of stock options	2,364	115	542
Distribution of treasury stock for deferred compensation plan	77	130	74
Repayment of long-term Federal Home Loan Bank borrowings	(54,342)	(55,398)	(60,372)
Proceeds of long-term Federal Home Loan Bank borrowings	345,000	0	0
Redemption of issued trust preferred securities	0	(5,155)	0
Changes in:
Time deposits	(220,640)	(299,803)	(274,652)
Other deposits	89,395	237,001	250,380
Federal funds purchased, securities sold under agreements to repurchase and other short-term borrowings	115,792	60,196	32,986
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	215,450	(125,224)	(102,290)
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(15,460)	(203,926)	174,614
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	432,077	636,003	461,389
CASH AND CASH EQUIVALENTS AT END OF YEAR	$ 416,617	$ 432,077	$ 636,003