Goodwill and Other Intangible Assets (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Goodwill [Roll Forward]
Balance at December 31,	$ 460,044	$ 139,598
Balance at December 31,	460,044	460,044	139,598
Goodwill and Intangible Assets (Textual) [Abstract]
Amortization of Intangible Assets	2,172	2,914	347
Commercial [Member]
Goodwill [Roll Forward]
Balance at December 31,	384,721	384,721	73,827
Retail [Member]
Goodwill [Roll Forward]
Balance at December 31,	66,141	66,141	59,038
Wealth [Member]
Goodwill [Roll Forward]
Balance at December 31,	9,182	9,182	6,733
First Bank Branches [Member]
Goodwill [Roll Forward]
Goodwill acquired		48,347
Goodwill and Intangible Assets (Textual) [Abstract]
Goodwill acquired to be deductible for tax purposes	43,500
First Bank Branches [Member] | Commercial [Member]
Goodwill [Roll Forward]
Goodwill acquired		46,414
First Bank Branches [Member] | Retail [Member]
Goodwill [Roll Forward]
Goodwill acquired		1,933
First Bank Branches [Member] | Wealth [Member]
Goodwill [Roll Forward]
Goodwill acquired		0
Midwest [Member]
Goodwill [Roll Forward]
Goodwill acquired		272,099
Goodwill and Intangible Assets (Textual) [Abstract]
Goodwill acquired to be deductible for tax purposes	272,099
Midwest [Member] | Commercial [Member]
Goodwill [Roll Forward]
Goodwill acquired		264,480
Midwest [Member] | Retail [Member]
Goodwill [Roll Forward]
Goodwill acquired		5,170
Midwest [Member] | Wealth [Member]
Goodwill [Roll Forward]
Goodwill acquired		$ 2,449