Subsequent Events (unaudited) Citizens Republic Acquisition (Details) (Citizens Republic Bancorp [Member], Subsequent Event [Member], USD $)	Feb. 04, 2013
Issuance of Debt [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount	$ 250,000,000	[1],[2]
Debt Instrument, Interest Rate, Stated Percentage	4.35%	[1],[2]
Issuance of Equity [Member]
Subsequent Event [Line Items]
Shares, Issued	4,000,000	[3]
Total gross proceeds from issuance of depositary shares	100,000,000	[3]
Non-Cumulative Perpetual Preferred Stock Dividend Rate	5.875%	[3]
Preferred Stock, Liquidation Preference Per Share	$ 1,000	[3]
Preferred Stock, Liquidation Preference, Value	$ 25	[3]

[1] The Corporation must redeem all of the Subordinated Notes if the Merger does not occur on or prior to June 12, 2013 or such later date as determined by the Corporation’s board of directors, but not later than September 12, 2013, or if the Merger Agreement is terminated at any time prior to that date, for the redemption price equal to 101% of the aggregate principal amount plus accrued interest up to, but excluding, the date of redemption.

[2] 4.35% subordinated notes due February 4, 2023

[3] Each depositary share represents a 1/40th ownership interest in a share of the Corporation's 5.875% Non-Cumulative Perpetual Preferred Stock, Series A, without par value, $1,000 liquidation preference per share (equivalent to $25 per depositary share) ("Preferred Stock").