Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Interest income:
Loans, including fees	$ 401,364	$ 397,855	$ 409,651
Securities:
Taxable	132,432	127,072	121,402
Tax-exempt	93,412	91,672	81,311
Interest-bearing deposits	4,300	6,357	4,901
Federal funds sold and resell agreements	104	61	74
Total interest income	631,612	623,017	617,339
Interest expense:
Deposits	18,099	22,179	29,973
Federal funds purchased and repurchase agreements	140	312	437
Junior subordinated deferrable interest debentures	6,806	6,783	6,982
Other long-term borrowings	1,706	11,967	16,488
Total interest expense	26,751	41,241	53,880
Net interest income	604,861	581,776	563,459
Provision for loan losses	10,080	27,445	43,611
Net interest income after provision for loan losses	594,781	554,331	519,848
Non-interest income:
Trust and investment management fees	83,317	78,297	72,321
Service charges on deposit accounts	83,392	86,125	91,025
Insurance commissions and fees	39,948	35,421	34,015
Interchange and debit card transaction fees	16,933	29,625	30,542
Other charges, commissions and fees	30,180	27,750	25,380
Net gain (loss) on securities transactions	4,314	6,414	6
Other	30,703	26,370	28,744
Total non-interest income	288,787	290,002	282,033
Non-interest expense:
Salaries and wages	258,752	252,028	239,589
Employee benefits	57,635	52,939	52,352
Net occupancy	48,975	46,968	46,166
Furniture and equipment	55,279	51,469	47,651
Deposit insurance	11,087	12,714	20,451
Intangible amortization	3,896	4,387	5,125
Other	139,469	137,593	124,207
Total non-interest expense	575,093	558,098	535,541
Income before income taxes	308,475	286,235	266,340
Income taxes	70,523	68,700	57,576
Net income (loss)	$ 237,952	$ 217,535	$ 208,764
Earnings per common share:
Basic	$ 3.87	$ 3.55	$ 3.44
Diluted	$ 3.86	$ 3.54	$ 3.44