Consolidated Statements of Earnings (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
INTEREST INCOME:
Interest and fees on loans	$ 102,172	$ 98,767	$ 92,715
Interest on investment securities:
Taxable	31,318	37,721	36,227
Exempt from federal income tax	25,552	22,312	19,216
Interest on federal funds sold and interest-bearing deposits in banks	754	1,221	1,541
Income, total	159,796	160,021	149,699
INTEREST EXPENSE:
Interest on deposits	4,877	7,822	13,071
Other	235	202	457
Total interest expense	5,112	8,024	13,528
Net interest income	154,684	151,997	136,171
Provision for loan losses	3,484	6,626	8,962
Net interest income after provision for loan losses	151,200	145,371	127,209
NONINTEREST INCOME:
Trust fees	14,464	12,671	10,809
Service charges on deposit accounts	16,693	17,689	20,104
ATM, interchange and credit card fees	15,187	13,587	11,276
Real estate mortgage operations	5,094	3,943	3,812
Net gain on sale of available-for-sale securities	2,772	492	363
Net gain (loss) on sale of foreclosed assets	(350)	(1,315)	457
Other	3,349	4,371	2,657
Total noninterest income	57,209	51,438	49,478
NONINTEREST EXPENSE:
Salaries and employee benefits	58,269	56,256	52,641
Net occupancy expense	7,076	6,862	6,442
Equipment expense	8,790	7,800	7,476
FDIC insurance premiums	2,220	2,646	4,000
ATM, interchange and credit card expenses	5,448	4,918	3,779
Professional and service fees	3,044	3,232	2,839
Printing, stationery and supplies	1,970	1,831	1,717
Amortization of intangible assets	149	402	609
Other expenses	22,083	20,677	18,753
Total noninterest expense	109,049	104,624	98,256
EARNINGS BEFORE INCOME TAXES AND EXTRAORDINARY ITEM	99,360	92,185	78,431
INCOME TAX EXPENSE	25,135	23,816	20,068
NET EARNINGS BEFORE EXTRAORDINARY ITEM	74,225	68,369	58,363
EXTRAORDINARY ITEM - EXPROPRIATION OF LAND, NET OF INCOME TAXES OF $697			1,296
Net earnings	$ 74,225	$ 68,369	$ 59,659
NET EARNINGS PER SHARE, BASIC BEFORE EXTRAORDINARY ITEM	$ 2.36	$ 2.17	$ 1.87
NET EARNINGS PER SHARE, ASSUMING DILUTION BEFORE EXTRAORDINARY ITEM	$ 2.36	$ 2.17	$ 1.87
NET EARNINGS PER SHARE, BASIC	$ 2.36	$ 2.17	$ 1.91
NET EARNINGS PER SHARE, ASSUMING DILUTION	$ 2.36	$ 2.17	$ 1.91