Shareholders' Equity (Narrative) (Details) (USD $)	0 Months Ended		1 Months Ended	3 Months Ended								12 Months Ended				1 Months Ended							1 Months Ended			12 Months Ended			0 Months Ended	1 Months Ended
	Mar. 15, 2011	Dec. 19, 2008	Mar. 31, 2012	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 07, 2010	Dec. 31, 2012 HPK Financial Corporation [Member]	Aug. 31, 2012 Great Lakes Advisors, Inc [Member]	Jul. 31, 2011 Great Lakes Advisors, Inc [Member]	Sep. 30, 2011 Elgin State Bancorp, Inc [Member]	Aug. 31, 2008 Series A Preferred Stock [Member]	Dec. 31, 2012 Series A Preferred Stock [Member]	Dec. 31, 2011 Series A Preferred Stock [Member]	Mar. 31, 2012 Series C Preferred Stock [Member]	Dec. 31, 2012 Series C Preferred Stock [Member]	Dec. 31, 2011 Series C Preferred Stock [Member]	Dec. 31, 2010 Equity Component [Member]	Dec. 31, 2012 Maximum [Member]	Dec. 31, 2012 Minimum [Member]	Feb. 21, 2013 Subsequent Event [Member]	Jan. 31, 2013 Subsequent Event [Member]
Shareholders' Equity [Line Items]
Tangible equity units sold (in shares)															4,600,000
Percentage of tangible equity units sold															7.50%
Tangible equity unit public offering price per unit (in usd per share)															$ 50.00
Tangible equity unit, quarterly cash payments														$ 222,700,000
Percentage of fair value of debt component quarterly cash payments														7.50%
Discount rate on debt component															9.50%
Risk-free rate												0.70%	1.00%	2.50%												0.95%
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												4 years 6 months	4 years 4 months 24 days	6 years 2 months 12 days												3 years 0 months 7 days
Junior subordinated amortizing note, initial principal amount															9.728182
Quarterly installments on amortizing note	0.989583													0.9375
Settlement rate																											1.6666	1.3333
Number of consecutive trading days												20 days
Amount to be reclassified from additional paid-in capital to common stock (in usd per share)												$ 1
Non-cumulative perpetual convertible preferred stock issued (in shares)																				50,000			126,500
Preferred stock, liquidation value (in usd per share)																				$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 0
Liquidation of preference shares, private transactions																				$ 50,000,000			$ 126,500,000
Preferred stock, dividend rate, percentage																				8.00%			5.00%
Preferred stock convertible into common stock, option of holder at a conversion rate																				38.88			24.3132
Warrant for purchase of shares (in shares)		1,643,295		1,643,295								1,643,295
Exercise price of common stock (in usd per share)		$ 22.82
Warrant termination period		10 years
Warrants holders common stock purchase price (in usd per share)												$ 30.50
Warrants exercised (in shares)			18,000
Warrants outstanding (in shares)				1,000				19,000				1,000	19,000
Shares issued in acquisitions																372,530	25,493	529,087	353,650
Cash dividends declared per common share (in usd per share)				$ 0	$ 0.09	$ 0	$ 0.09	$ 0	$ 0.09	$ 0	$ 0.09	$ 0.18	$ 0.18	$ 0.18																$ 0.09
Common Stock Dividends Per Share Declared Annualized																														$ 0.18
Dividends paid (in usd per share)																													$ 0.09
Debt Instrument, Maturity Date														Dec. 15, 2013
Extended Installment Period On Amortizing Note												Dec. 15, 2015
Dividends Payable, Date to be Paid																													Feb. 21, 2013
Dividends Payable, Date of Record																													Feb. 07, 2013