Goodwill and Intangible Assets (Details Textuals) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Goodwill and Intangible Assets (Textuals) [Abstract]
Goodwill	$ 460,044,000	$ 460,045,000	$ 460,044,000	$ 460,045,000	$ 460,044,000
Amortization of intangibles	543,000	669,000	1,086,000	903,000
Estimated Amortization Expense- 2011			1,100,000
Estimated Amortization Expense- 2012			1,900,000
Estimated Amortization Expense- 2013			1,200,000
Estimated Amortization Expense- 2014			1,100,000
Estimated Amortization Expense- 2015			1,000,000
First Bank Branches [Member]
Goodwill [Line Items]
Goodwill acquired to be deductible for tax purposes	43,500,000		43,500,000
Midwest [Member]
Goodwill [Line Items]
Acquired goodwill fair value adjustments			272,100,000
Goodwill acquired to be deductible for tax purposes	48,300,000		48,300,000
Midwest [Member] | Core deposit intangibles [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Fair value of intangible assets		$ 7,400,000		$ 7,400,000
Estimated useful life of intangible assets		10