Segment Information (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment Reporting Information [Line Items]
Net interest income	$ 85,680	$ 87,567	$ 259,885	$ 263,471
Provision for loan losses	7,978	12,259	23,631	37,752
Noninterest income	44,272	43,979	127,075	127,295
Noninterest expense	85,481	84,423	246,847	245,212
Income before income taxes	36,493	34,864	116,482	107,802
Income taxes	9,525	9,004	33,899	32,326
Net income	26,968	25,860	82,583	75,476
Average assets	9,572,456	9,217,923	9,565,527	9,267,326
Depreciation and amortization	6,611	6,800	18,523	18,626
General Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	84,509	86,453	256,449	260,128
Provision for loan losses	7,984	12,264	23,624	37,755
Noninterest income	30,686	30,964	88,205	89,390
Noninterest expense	72,916	73,923	212,263	213,406
Income before income taxes	34,295	31,230	108,767	98,357
Income taxes	8,760	7,710	31,198	28,991
Net income	25,535	23,520	77,569	69,366
Average assets	9,423,743	9,061,255	9,417,382	9,109,516
Depreciation and amortization	6,207	6,335	17,276	17,230
Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest income	1,094	1,041	3,234	3,146
Provision for loan losses	(6)	(5)	7	(3)
Noninterest income	6,078	5,289	18,000	16,404
Noninterest expense	6,819	4,752	17,946	14,790
Income before income taxes	359	1,583	3,281	4,763
Income taxes	71	528	1,047	1,587
Net income	288	1,055	2,234	3,176
Average assets	81,527	87,863	82,323	90,634
Depreciation and amortization	49	69	162	204
Insurance [Member]
Segment Reporting Information [Line Items]
Net interest income	77	73	202	197
Provision for loan losses	0	0	0	0
Noninterest income	7,508	7,726	20,870	21,501
Noninterest expense	5,746	5,748	16,638	17,016
Income before income taxes	1,839	2,051	4,434	4,682
Income taxes	694	766	1,654	1,748
Net income	1,145	1,285	2,780	2,934
Average assets	67,186	68,805	65,822	67,176
Depreciation and amortization	$ 355	$ 396	$ 1,085	$ 1,192