Shareholders' Equity And Earnings Per Share (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Thousands								1 Months Ended					3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 20, 2015	Aug. 06, 2015	May. 21, 2015	May. 07, 2015	Feb. 19, 2015	Feb. 05, 2015	Dec. 19, 2008	Jul. 31, 2015	Jun. 30, 2015	Apr. 30, 2015	Jan. 31, 2015	Mar. 31, 2012	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Jun. 25, 2015
Temporary Equity [Line Items]
Cash dividends declared per common share								$ 0.11		$ 0.11	$ 0.11		$ 0.11	$ 0.10	$ 0.33	$ 0.30
Common stock dividends per share declared annualized								$ 0.44		$ 0.44	$ 0.44
Dividends payable, date to be paid	Aug. 20, 2015		May 21, 2015		Feb. 19, 2015
Dividends payable, date of record		Aug. 06, 2015		May 07, 2015		Feb. 05, 2015
Community Financial Shares, Inc.
Temporary Equity [Line Items]
Common stock, shares issued, acquisition								388,573
Delavan Bancshares
Temporary Equity [Line Items]
Common stock, shares issued, acquisition											422,122
US Treasury
Temporary Equity [Line Items]
Warrants outstanding							1,643,295						383,352		383,352
Investment warrants, exercise price							$ 22.82
Warrant termination period							10 years
Warrants exercised															554,065
Common stock, shares, issued from exercise of warrant shares															304,915
Series D Preferred Stock
Temporary Equity [Line Items]
Preferred stock, shares issued																		5,000,000,000,000
Preferred stock, liquidation value per share													$ 25	$ 0	$ 25	$ 0	$ 0	$ 25
Preferred stock, value													$ 125,000	$ 0	$ 125,000	$ 0	$ 0	$ 125,000
Preferred stock, Dividend payment terms									quarterly
Preferred stock, dividend rate, percentage									6.50%
Series C Preferred Stock
Temporary Equity [Line Items]
Preferred stock, shares issued												126,500
Preferred stock, liquidation value per share												$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 1,000
Preferred stock, value												$ 126,500	$ 126,312	$ 126,467	$ 126,312	$ 126,467	$ 126,467
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															155		10
Common stock, shares, conversion of preferred stock															3,767		244
London Interbank Offered Rate (LIBOR) | Series D Preferred Stock
Temporary Equity [Line Items]
Preferred stock, dividend rate, percentage, variable spread									4.06%