Acquisitions Allocation of Purchase Price (Details) - USD ($) $ in Thousands	May. 31, 2015	Apr. 01, 2015	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Schedule of Purchase Price Allocation [Line Items]
Goodwill			$ 285,512	$ 180,128	$ 120,164
Short-term borrowings			532,291	389,467	305,422
Other Borrowings			$ 148,490	$ 0	$ 0
Monarch Community Bancorp [Member]
Schedule of Purchase Price Allocation [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		$ 32,171
Business Combination, Acquired Receivables, Fair Value		121,783
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		3,064
Business Combination, Deferred Tax Asset, Net Operating Loss		7,900
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent		2,314
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables		6,972
Goodwill		5,383
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Mortgage Servicing Rights Asset		1,284
Core deposit intangible assets acquired, business combination		1,930
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		182,801
Business Combination Deposits Assumed		144,311
Other Borrowings		8,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other		3,299
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		155,610
Business Combination, Consideration Transferred		$ 27,191
Lake Michigan Financial Corp [Member]
Schedule of Purchase Price Allocation [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	$ 39,301
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities	66,699
Business Combination, Acquired Receivables, Fair Value	985,542
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	13,673
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent	14,888
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	38,449
Goodwill	100,002
Core deposit intangible assets acquired, business combination	7,303
Bank Owned Life Insurance	23,844
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	1,289,701
Business Combination Deposits Assumed	924,697
Short-term borrowings	30,000
Other Borrowings	124,723
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other	22,887
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	1,102,307
Business Combination, Consideration Transferred	$ 187,394