Shareholders' Equity And Earnings Per Share (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended					3 Months Ended		12 Months Ended
	Feb. 25, 2016	Feb. 11, 2016	Dec. 19, 2008	Jan. 31, 2016	Jul. 31, 2015	Jun. 30, 2015	Jan. 31, 2015	Mar. 31, 2012	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Temporary Equity [Line Items]
Cash dividends declared per common share				$ 0.12					$ 0.12	$ 0.11
Common stock dividends per share declared annualized				$ 0.48
Dividends payable, date to be paid	Feb. 25, 2016
Dividends payable, date of record		Feb. 11, 2016
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						367,432
Investment warrants, exercise price			$ 22.82
Warrant termination period			10 years
Warrants exercised									0
Series D Preferred Stock
Temporary Equity [Line Items]
Preferred stock, shares issued						5,000,000,000,000
Preferred stock, liquidation value per share						$ 25			$ 25	$ 0	$ 25
Preferred stock, value						$ 125,000			$ 125,000	$ 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
Preferred stock, value								$ 126,500	$ 126,257	$ 126,427	$ 126,287
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									30		180
Common stock, shares, conversion of preferred stock									729		4,374
London Interbank Offered Rate (LIBOR) | Series D Preferred Stock
Temporary Equity [Line Items]
Preferred stock, dividend rate, percentage, variable spread						4.06%