Stockholders' Equity (Details) (USD $)	12 Months Ended				0 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Nov. 12, 2013 Merger with CFS Bancorp, Inc. (Citizens)	Nov. 22, 2013 Series B Preferred Stock	Jul. 02, 2013 Series B Preferred Stock	Jan. 03, 2013 Series B Preferred Stock	Sep. 22, 2011 Series B Preferred Stock	Dec. 31, 2013 Series B Preferred Stock	Dec. 31, 2013 Subsidiaries	Nov. 12, 2013 CFS Bancorp Merger with CFS Bancorp, Inc. (Citizens)
Class of Stock [Line Items]
Amount Available for Dividend Distribution without Affecting Capital Adequacy Requirements											$ 40,982,000
Total Stockholders' Equity	634,923,000	552,236,000	514,467,000	454,408,000							744,116,000
Stockholders' Equity restricted from dividend distribution	703,134,000
Dividend reinvestment and stock purchase plan, Stockholder's maximum amount of cash payments per quarter in purchase of common stock	2,500
Number of new stock issued during the period (shares)									90,782.94
Preferred Stock, liquidation value (in dollars per share)									$ 1,000
Number of new stock issued during the period value			21,165,000						90,782,940
Preferred stock redeemed (in shares)						34,043	34,044	22,695.94
Price of preferred stock redeemed	491,000	235,000	126,000			34,043,000	34,044,000	22,695,940
Preferred Stock, shares outstanding							34,043	68,087		0
Series B Preferred Stock remaining liquidation amount							34,000,000	68,000,000
Percentage of Interest Acquired					100.00%
Percentage of common stock received per shares owned through acquisition												0.65%
Stock issued as a part of acquisition (in shares)					7,100,000
Value of stock issued as a part of acquisition	$ 135,642,000				$ 135,642,000