Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Segment	Sep. 30, 2013
Segment Reporting Information [Line Items]
Number of segments in which the business operates			3
Net interest income	$ 106,229	$ 98,429	$ 306,421	$ 286,632
Provision for loan losses, net	4,203	(332)	7,596	(9,568)
Noninterest income	42,893	47,133	131,111	135,186
Noninterest expense	100,194	101,524	304,573	310,864
Income before income taxes	44,725	44,370	125,363	120,522
Income taxes	11,136	11,336	29,874	31,501
Net Income	33,589	33,034	95,489	89,021
Selected Financial Information [Abstract]
Average assets	12,091,213	11,759,108	11,994,315	11,450,755
Depreciation and amortization	9,132	9,483	27,088	27,800
General Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	105,672	98,135	305,422	285,915
Provision for loan losses, net	4,203	(332)	7,596	(9,568)
Noninterest income	25,663	31,443	81,685	90,352
Noninterest expense	86,935	89,198	265,067	274,545
Income before income taxes	40,197	40,712	114,444	111,290
Income taxes	9,535	10,040	26,012	28,216
Net Income	30,662	30,672	88,432	83,074
Selected Financial Information [Abstract]
Average assets	12,013,572	11,688,102	11,928,029	11,383,231
Depreciation and amortization	8,896	9,186	26,289	26,905
Wealth Management [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	467	192	749	480
Noninterest income	7,989	7,459	23,784	21,338
Noninterest expense	6,303	6,294	19,357	18,230
Income before income taxes	2,153	1,357	5,176	3,588
Income taxes	712	446	1,714	1,178
Net Income	1,441	911	3,462	2,410
Selected Financial Information [Abstract]
Average assets	263	461	1,478	256
Depreciation and amortization	48	39	143	118
Insurance [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	90	102	250	237
Noninterest income	9,241	8,231	25,642	23,496
Noninterest expense	6,956	6,032	20,149	18,089
Income before income taxes	2,375	2,301	5,743	5,644
Income taxes	889	850	2,148	2,107
Net Income	1,486	1,451	3,595	3,537
Selected Financial Information [Abstract]
Average assets	77,378	70,545	64,808	67,268
Depreciation and amortization	$ 188	$ 258	$ 656	$ 777