Shareholders' Equity And Earnings Per Share (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Thousands						1 Months Ended							3 Months Ended		6 Months Ended		12 Months Ended
	May 26, 2016	May 12, 2016	Feb. 25, 2016	Feb. 11, 2016	Dec. 19, 2008	Jun. 30, 2016	Apr. 30, 2016	Jan. 31, 2016	Jul. 31, 2015	Jun. 30, 2015	Jan. 31, 2015	Mar. 31, 2012	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Temporary Equity [Line Items]
Stock issued in public offering, shares						3,000,000
Proceeds from the issuance of common stock, net						$ 152,800									$ 152,823	$ 0
Cash dividends declared per common share (usd per share)							$ 0.12	$ 0.12					$ 0.12	$ 0.11	$ 0.24	$ 0.22
Common stock dividends per share declared annualized (usd per share)							$ 0.48	$ 0.48
Dividends payable, date to be paid	May 26, 2016		Feb. 25, 2016
Dividends payable, date of record		May 12, 2016		Feb. 11, 2016
Community Financial Shares, Inc.
Temporary Equity [Line Items]
Common stock, acquisition, shares issued									388,573
Delavan Bancshares
Temporary Equity [Line Items]
Common stock, acquisition, shares issued											422,122
US Treasury
Temporary Equity [Line Items]
Warrants outstanding, shares					1,643,295	367,432							367,432		367,432
Investment warrants, exercise price (usd per share)					$ 22.82
Warrant termination period					10 years
Warrants exercised, shares															0
Series D Preferred Stock
Temporary Equity [Line Items]
Preferred stock, shares issued										5,000,000				5,000,000		5,000,000
Preferred stock, liquidation value per share (usd per share)						$ 25				$ 25			$ 25	$ 25	$ 25	$ 25	$ 25
Preferred stock, value						$ 125,000				$ 125,000			$ 125,000	$ 125,000	$ 125,000	$ 125,000	$ 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 (usd per share)						$ 1,000				$ 1,000		$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 1,000
Preferred stock, value						$ 126,257				$ 126,312		$ 126,500	$ 126,257	$ 126,312	$ 126,257	$ 126,312	$ 126,287
Preferred stock, Dividend payment terms												quarterly
Preferred stock, dividend rate, percentage												5.00%
Convertible preferred stock, rate of conversion, shares												24.6213
Preferred stock, shares converted															30		180
Common stock, conversion of preferred stock, shares															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%