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:
Interest and fees on loans	$ 192,710	$ 192,981	$ 178,703
Interest and dividends on taxable investments	65,165	55,634	47,241
Interest and dividends on nontaxable investments	23,525	22,354	22,337
Total interest income	281,400	270,969	248,281
Interest expense:
Interest on deposits	18,162	26,156	30,559
Interest on borrowings	30,098	29,599	30,078
Interest on subordinated debt held by unconsolidated subsidiary trusts	2,716	5,801	5,960
Total interest expense	50,976	61,556	66,597
Net interest income	230,424	209,413	181,684
Less: provision for loan losses	9,108	4,736	7,205
Net interest income after provision for loan losses	221,316	204,677	174,479
Noninterest income:
Deposit service fees	46,064	42,334	43,358
Other banking services	4,069	4,651	5,985
Benefit trust administration, consulting and actuarial fees	35,946	31,601	29,616
Wealth management services	12,876	10,697	9,833
Gain (loss) on investment securities and debt extinguishments, net	291	(61)	0
Total noninterest income	99,246	89,222	88,792
Noninterest expenses:
Salaries and employee benefits	112,034	102,278	91,399
Occupancy and equipment	25,799	24,502	22,933
Data processing and communications	23,696	20,525	20,720
Amortization of intangible assets	4,607	4,381	5,957
Legal and professional fees	7,950	5,889	5,532
Office supplies and postage	5,742	5,246	5,469
Business development and marketing	5,919	5,931	5,237
FDIC insurance premiums	3,804	3,920	5,838
Acquisition expenses	5,747	4,831	860
Other	16,459	12,869	12,941
Total noninterest expenses	211,757	190,372	176,886
Income before income taxes and equity in undistributed net income of subsidiaries	108,805	103,527	86,385
Income taxes	31,737	30,385	23,065
Net income	$ 77,068	$ 73,142	$ 63,320
Basic earnings per share (in dollars per share)	$ 1.95	$ 2.03	$ 1.91
Diluted earnings per share (in dollars per share)	$ 1.93	$ 2.01	$ 1.89
Cash dividends declared per share (in dollars per share)	$ 1.06	$ 1.00	$ 0.94