Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
ASSETS
Cash and due from banks	$ 187,416	$ 203,545	$ 225,547
Interest-bearing deposits with banks	1,699,265	1,710,350	1,737,559
Federal funds sold	1,000		3,000
Securities (fair value: $550,194, $524,861, and $587,100, respectively)	550,125	524,783	587,018
Loans:
Total loans (net of unearned interest)	3,857,742	3,860,831	3,542,270
Allowance for loan losses	(41,557)	(40,889)	(39,924)
Loans, net	3,816,185	3,819,942	3,502,346
Premises and equipment, net	122,786	121,341	121,354
Other real estate owned	6,246	7,859	7,328
Intangible assets, net	10,158	10,635	11,549
Goodwill	44,962	44,962	45,118
Accrued interest receivable and other assets	131,977	131,555	134,222
Total assets	6,570,120	6,574,972	6,375,041
Deposits:
Noninterest-bearing	2,319,445	2,411,066	2,133,583
Interest-bearing	3,564,356	3,493,638	3,604,267
Total deposits	5,883,801	5,904,704	5,737,850
Short-term borrowings	2,043	3,982	8,603
Long-term borrowings			2,000
Accrued interest payable and other liabilities	35,793	30,168	31,672
Junior subordinated debentures	26,804	26,804	26,804
Total liabilities	5,948,441	5,965,658	5,806,929
Commitments and contingent liabilities
Stockholders' equity:
Common stock, $1.00 par, 20,000,000 shares authorized; shares issued and outstanding: 15,512,545, 15,504,513 and 15,363,728, respectively	15,512	15,504	15,364
Capital surplus	97,477	96,841	89,951
Retained earnings	503,758	492,776	458,857
Accumulated other comprehensive income, net of income tax of $3,110, $2,644 and $2,486, respectively	4,932	4,193	3,940
Total stockholders' equity	621,679	609,314	568,112
Total liabilities and stockholders' equity	6,570,120	6,574,972	6,375,041
Senior Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value
Cumulative Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value