Business Combinations (All Other Acquisitions) (Details) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2012	Jul. 31, 2011 Great Lakes Advisors [Member]	Sep. 30, 2011 Elgin State Bancorp, Inc [Member]	Apr. 13, 2011 River City Mortgage LLC [Member]	Feb. 03, 2011 Woodfield Planning Corporation [Member]	Mar. 31, 2012 Chicago Trust Company [Member]
Business Acquisition [Line Items]
Fair value of assets acquired, at the acquisition date			$ 263,200,000
Fair value of loans acquired, at the acquisition date			146,700,000
Fair value of liabilities assumed, at the acquisition date			248,400,000
Additional goodwill recorded on acquisition	1,827,000		5,000,000
Business acquisition, assets acquired		26,000,000
Approximate fair value of assumed liabilities, deposits			241,100,000
Business acquisition, liabilities assumed		8,800,000
Assets under administration acquired		2,400,000,000				160,000,000
Business acquisition, goodwill amount		15,700,000				1,800,000
Mortgage loans				$ 500,000,000	$ 180,000,000