Segment Information (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Segment Reporting Information [Line Items]
Net interest income	$ 87,830	$ 88,486	$ 174,205	$ 175,904
Provision for loan losses	8,116	10,398	15,653	25,493
Noninterest income	46,432	44,947	82,803	83,316
Noninterest expense	81,348	84,428	161,366	160,789
Income before income taxes	44,798	38,607	79,989	72,938
Income taxes	13,196	12,446	24,374	23,322
Net income	31,602	26,161	55,615	49,616
Average assets	9,614,125	9,250,501	9,562,005	9,292,437
Depreciation and amortization	6,059	6,028	11,912	11,826
General Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	86,699	87,363	171,940	173,675
Provision for loan losses	8,100	10,403	15,640	25,491
Noninterest income	33,704	32,377	57,519	58,426
Noninterest expense	70,527	73,906	139,347	139,483
Income before income taxes	41,776	35,431	74,472	67,127
Income taxes	12,134	11,334	22,438	21,281
Net income	29,642	24,097	52,034	45,846
Average assets	9,465,636	9,093,036	9,414,149	9,134,009
Depreciation and amortization	5,651	5,563	11,069	10,895
Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest income	1,067	1,054	2,140	2,105
Provision for loan losses	16	(5)	13	2
Noninterest income	5,851	5,681	11,922	11,115
Noninterest expense	5,340	5,037	11,127	10,038
Income before income taxes	1,562	1,703	2,922	3,180
Income taxes	520	564	976	1,059
Net income	1,042	1,139	1,946	2,121
Average assets	82,986	91,454	82,727	92,042
Depreciation and amortization	51	67	113	135
Insurance [Member]
Segment Reporting Information [Line Items]
Net interest income	64	69	125	124
Provision for loan losses	0	0	0	0
Noninterest income	6,877	6,889	13,362	13,775
Noninterest expense	5,481	5,485	10,892	11,268
Income before income taxes	1,460	1,473	2,595	2,631
Income taxes	542	548	960	982
Net income	918	925	1,635	1,649
Average assets	65,503	66,011	65,129	66,386
Depreciation and amortization	$ 357	$ 398	$ 730	$ 796