Business Combinations Business Combinations (Narrative) (Details) (USD $)	12 Months Ended				0 Months Ended	3 Months Ended		12 Months Ended							9 Months Ended				9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended						12 Months Ended
	Dec. 31, 2013 Branch	Dec. 31, 2012	Dec. 31, 2011	Apr. 12, 2013	Apr. 15, 2013 Citizens Republic Bancorp	Dec. 31, 2013 Citizens Republic Bancorp	Jun. 30, 2013 Citizens Republic Bancorp	Dec. 31, 2013 Citizens Republic Bancorp	Sep. 30, 2013 Citizens Republic Bancorp	Apr. 12, 2013 Citizens Republic Bancorp Branch	Feb. 04, 2013 Citizens Republic Bancorp	Dec. 31, 2012 Citizens Republic Bancorp	Apr. 12, 2013 Citizens Republic Bancorp	Dec. 31, 2013 Citizens Republic Bancorp	Dec. 31, 2013 Michigan and Wisconsin Citizens Republic Bancorp	Dec. 31, 2013 Acquired Impaired Loans	Dec. 31, 2012 Acquired Impaired Loans	Apr. 12, 2013 Acquired Impaired Loans Citizens Republic Bancorp	Sep. 30, 2013 Junior Subordinated Debt Citizens Republic Bancorp	Dec. 31, 2013 Junior Subordinated Debt Citizens Republic Bancorp	Sep. 30, 2013 Minimum Junior Subordinated Debt Citizens Republic Bancorp	Dec. 31, 2013 Minimum Junior Subordinated Debt Citizens Republic Bancorp	Sep. 30, 2013 Maximum Junior Subordinated Debt Citizens Republic Bancorp	Dec. 31, 2013 Maximum Junior Subordinated Debt Citizens Republic Bancorp	Dec. 31, 2013 Loans and Finance Receivables [Member] Citizens Republic Bancorp	Dec. 31, 2013 Property, Plant and Equipment [Member] Citizens Republic Bancorp	Dec. 31, 2013 Other Assets [Member] Citizens Republic Bancorp	Dec. 31, 2013 Other Liabilities [Member] Citizens Republic Bancorp	Apr. 12, 2013 Acquired Impaired Loans Citizens Republic Bancorp	Dec. 31, 2013 Employee Severance [Member] Citizens Republic Bancorp	Dec. 31, 2013 professional services [Member] Citizens Republic Bancorp	Dec. 31, 2013 Contract Termination [Member] Citizens Republic Bancorp	Apr. 12, 2013 Core Deposits Citizens Republic Bancorp	Dec. 31, 2013 Acquired Loans Impaired loans [Member]
Business Combinations [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles										$ 84,774,000																							$ 70,800,000
Business Combination, Acquired Receivables, Fair Value										4,617,004,000								819,715,000											1,100,000,000
Goodwill, Purchase Accounting Adjustments								5,400,000																	(7,300,000)	(200,000)	1,100,000	(1,000,000)
Goodwill, Subsequent Recognition of Deferred Tax Asset								3,400,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net																601,000,000	0	819,715,000
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Deferred Tax Asset, Net						(348,239,000)		(348,239,000)		348,200,000		0
Assets	23,909,027,000	14,913,012,000								9,600,000,000
Number of Branches	404									219
Business Acquisition, Equity Interest Issued or Issuable, Share Conversion Ratio										1.37
Stock issued for Citizens acquisition										55,468,283
Amount of Citizens TARP Preferred Stock										300,000,000
Accumulated but unpaid interest and dividends related to Citizens TARP Preferred Stock										55,400,000
Debt Instrument, Face Amount											250,000,000
Debt Instrument, Interest Rate, Stated Percentage											4.35%
Total gross proceeds from issuance of depositary shares											100,000,000
Interest rate of Non-Cumulative Perpetual Preferred Stock, Series A											5.875%
Class of Warrant or Right, Number of Securities Called by Warrants or Rights				2,408,203						2,408,203			1,757,812.5	2,471,681
Goodwill, Acquired During Period						279,775,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment										138,536,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent										313,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent										(51,300,000)
Deferred Tax Assets, Net	329,909,000	7,111,000								261,700,000
Net Operating Loss and Tax Credit Carryforwards included in Acquired Deferred Tax Asset										224,800,000
Business combination, deferred tax asset fair market value adjustment										86,500,000
Interest Income, Operating															222,700,000
Net income	183,684,000	134,106,000	119,558,000												106,400,000
Business Combination, Acquisition Related Costs								75,100,000																						21,600,000	20,200,000	23,600,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance																		1,231,172,000																800,000,000
Certain Loans Acquired in Transfer, Nonaccretable Difference																		(279,899,000)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities										3,202,575,000
Amount of securities sold subsequent to acquisition							2,200,000,000
Repurchase of securities subsequent to acquisition							1,500,000,000
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Federal Home Loan Bank Advances										719,300,000
Repayments of Federal Home Loan Bank Borrowings					652,500,000
Federal home loan bank advances retained									66,800,000
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Subordinated Debt										74,500,000
Debt Instrument, Description of Variable Rate Basis																			LIBOR	LIBOR
Debt Instrument, Basis Spread on Variable Rate																					3.10%	3.10%	11.75%	11.75%
Debt Instrument, Interest Rate, Stated Percentage																			7.50%	7.50%
Business Combination Recognized Identifiable Assets Acquired And Liabilities Long Term Repurchase Agreements										$ 115,000,000