Shareholders' Equity (Narrative) (Details) - USD ($)					1 Months Ended							3 Months Ended								12 Months Ended
	Dec. 15, 2013	May. 01, 2013	Mar. 15, 2011	Dec. 19, 2008	Jan. 31, 2016	Jul. 31, 2015	Jun. 30, 2015	Jan. 31, 2015	Jul. 19, 2013	Mar. 31, 2012	Aug. 31, 2008	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010	Jun. 25, 2015	Dec. 07, 2010
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, net proceeds																								$ 222,700,000
Debt instrument, maturity date																				Jun. 15, 2020
Debt instrument, frequency of periodic payment																				quarterly			annual
Common stock, no par value									$ 0			$ 0				$ 0				$ 0	$ 0
Cash dividends declared per common share												$ 0.11	$ 0.11	$ 0.11	$ 0.11	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.44	$ 0.40	$ 0.18
Series A preferred stock
Shareholders' Equity [Line Items]
Preferred stock, shares issued											50,000
Preferred stock, liquidation value (in usd per share)											$ 1,000
Preferred stock, value, issued											$ 50,000,000
Preferred stock, dividend payment terms											quarterly
Preferred stock, dividend rate, percentage											8.00%
Convertible preferred stock, terms of conversion											38.88
Preferred stock, shares converted									50,000
Common stock, shares, conversion of preferred stock									1,944,000
Series C preferred stock
Shareholders' Equity [Line Items]
Preferred stock, shares issued										126,500		126,287				126,467				126,287	126,467
Preferred stock, liquidation value (in usd per share)										$ 1,000		$ 1,000				$ 1,000				$ 1,000	$ 1,000
Preferred stock, value, issued										$ 126,500,000		$ 126,287,000				$ 126,467,000				$ 126,287,000	$ 126,467,000
Preferred stock, dividend payment terms										quarterly
Preferred stock, dividend rate, percentage										5.00%
Convertible preferred stock, terms of conversion										24.3132
Preferred stock, shares converted																				180	10
Common stock, shares, conversion of preferred stock																				4,374	244
Series D preferred stock
Shareholders' Equity [Line Items]
Preferred stock, shares issued												5,000,000				0				5,000,000	0				5,000,000
Preferred stock, liquidation value (in usd per share)												$ 25				$ 0				$ 25	$ 0				$ 25
Preferred stock, value, issued												$ 125,000,000				$ 0				$ 125,000,000	$ 0				$ 125,000,000
Preferred stock, dividend payment terms							quarterly
Preferred stock, dividend rate, percentage							6.50%
Preferred stock, dividend rate, percentage, variable spread							4.06%
Community Financial Shares Inc.
Shareholders' Equity [Line Items]
Shares issued in acquisitions						388,573
Delavan Bancshares
Shareholders' Equity [Line Items]
Shares issued in acquisitions								422,122
First Lansing Bancorp, Inc.
Shareholders' Equity [Line Items]
Shares issued in acquisitions		648,286
Junior Subordinated Amortizing Notes
Shareholders' Equity [Line Items]
Debt instrument, maturity date																						Dec. 15, 2013		Dec. 15, 2013
Debt instrument, frequency of periodic payment																						quarterly
Contractual Rate	9.50%
Debt [Member] | Junior Subordinated Amortizing Notes
Shareholders' Equity [Line Items]
Debt instrument, maturity date																								Dec. 15, 2013
Debt instrument, frequency of periodic payment																								quarterly
Percentage of fair value of debt component quarterly cash payments																								7.50%
Discount rate on debt component																										9.50%
Junior subordinated amortizing note, initial principal amount																										$ 9.728182
Contractual Rate																										9.50%
Quarterly installments on amortizing note			$ 0.989583																					$ 0.9375
Equity [Member]
Shareholders' Equity [Line Items]
Debt instrument, maturity date																								Dec. 15, 2013
Fair Value Assumptions, Risk Free Interest Rate																								0.95%
Percent of dividend yield plus stock borrow cost																								0.85%
Fair Value Assumptions, Expected Term																								3 years 7 days
Settlement rate	1.3333
Number of consecutive trading days	20 days
Amount Per Share Reclassified From Surplus To Common Stock	$ 1.00
Minimum | Equity [Member]
Shareholders' Equity [Line Items]
Fair Value Assumptions, Expected Volatility Rate																								35.00%
Maximum | Equity [Member]
Shareholders' Equity [Line Items]
Fair Value Assumptions, Expected Volatility Rate																								45.00%
US Treasury
Shareholders' Equity [Line Items]
Warrants outstanding (in shares)				1,643,295								367,432								367,432
Exercise price of common stock (in usd per share)				$ 22.82
Warrant termination period				10 years
Warrants exercised (in shares)																				569,985
Common stock, shares, issued from exercise of warrant shares																				313,751
Subsequent Event
Shareholders' Equity [Line Items]
Cash dividends declared per common share					$ 0.12
Common stock dividends per share declared annualized (in usd per share)					$ 0.48
Dividends payable, date to be paid					Feb. 25, 2016
Dividends payable, date of record					Feb. 11, 2016