Shareholders' Equity And Earnings Per Share (Narrative) (Details) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended			1 Months Ended						0 Months Ended	1 Months Ended		3 Months Ended			3 Months Ended
	Mar. 15, 2011	Mar. 31, 2012	Mar. 31, 2012 Y	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2011	Jul. 31, 2011 Great Lakes Advisors, Inc [Member]	Sep. 30, 2011 Elgin State Bancorp, Inc [Member]	Aug. 31, 2008 Series A Preferred Stock [Member]	Mar. 31, 2012 Series A Preferred Stock [Member]	Dec. 31, 2011 Series A Preferred Stock [Member]	Mar. 31, 2011 Series A Preferred Stock [Member]	Dec. 19, 2008 Series B Preferred Stock [Member] Y	Dec. 31, 2010 Series B Preferred Stock [Member]	Mar. 31, 2012 Series C Preferred Stock [Member]	Mar. 31, 2012 Series C Preferred Stock [Member]	Dec. 31, 2011 Series C Preferred Stock [Member]	Mar. 31, 2011 Series C Preferred Stock [Member]	Mar. 31, 2012 Equity Component [Member] Y	Mar. 31, 2012 Maximum [Member]	Mar. 31, 2012 Minimum [Member]
Shareholders' Equity [Line Items]
Common stock, shares issued																122,690,000
Common Stock, shares issued in acquisition							529,087	353,650
Tangible equity unit, proceeds					$ 4,600,000
Rate on tangible equity units					7.50%
Tangible equity unit public offering price per unit					50.00
Net proceeds on sale of tangible equity units					222,700,000
Percentage of fair value of debt component quarterly cash payments			7.50%
Risk-free rate			0.70%																0.95%
Debt component maturity date			Dec. 15, 2013
Discount rate on debt component		9.50%	9.50%
Expected stock price volatility minimum																			35.00%
Expected stock price volatility maximum																			45.00%
Percent of dividend yield plus stock borrow cost																			0.85%
Equity term, years			4.5																3.02
Settlement rate, shares																				1.6666	1.3333
Junior subordinated amortizing note, initial principal amount		9.728182	9.728182
Junior subordinated amortizing note, bearing interest		9.50%	9.50%
Junior subordinated amortizing note, scheduled final installment payment date				Dec. 15, 2013
Quarterly installments on amortizing note	0.989583		0.9375
Extended installment period on amortizing note				Dec. 15, 2015
Number of consecutive trading days				20 days
Non-cumulative perpetual convertible preferred stock, issued									50,000						126,500	126,500
Preferred stock, liquidation value per share									$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 1,000		$ 1,000	$ 1,000	$ 1,000	$ 1,000
Liquidation of preference shares, private transactions									50,000,000
Liquidation of preference shares, equity offering															126,500,000
Preferred stock, dividend rate, percentage									8.00%						5.00%
Convertible preferred stock conversion rate of common stock to Series A preferred stock									38.88						24.3132
Treasury issued under capital purchase program													$ 250,000,000
Stock repurchased														250,000
Cumulative perpetual convertible preferred stocks, issued													250,000
Warrant for purchase of shares													1,643,295
Exercise price of common stock, per share													$ 22.82
Warrant termination period, years													10
Warrants holders common stock purchase price per share			$ 30.50
Warrants exercised		18,000
Warrants outstanding		1,000	1,000			19,000
Warrants expiration date			Feb. 01, 2013	Feb. 01, 2013