Business Combination - Narrative (Details) (USD $)	0 Months Ended	12 Months Ended
	Nov. 12, 2013 bank	Dec. 31, 2013
Business Acquisition [Line Items]
Value of stock issued as a part of acquisition		$ 135,642,000
Merger with CFS Bancorp, Inc. (Citizens)
Business Acquisition [Line Items]
Percentage of Interest Acquired	100.00%
Number of full service banking centers owned	20
Stock issued as a part of acquisition (in shares)	7,100,000
Value of stock issued as a part of acquisition	135,642,000
Core deposit intangible	7,313,000
Acquired intangible asset, expected useful life	10 years
Pro forma revenue		4,900,000
Pro forma nonrecurring expense		$ 9,500,000
CFS Bancorp | Merger with CFS Bancorp, Inc. (Citizens)
Business Acquisition [Line Items]
Percentage of common stock received per shares owned through acquisition	0.65%