Significant Accounting Policies (Business Combinations) (Details) - USD ($) $ in Thousands	May. 31, 2015	Apr. 01, 2015	Oct. 31, 2014	Apr. 30, 2010	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill acquired					$ 287,393	$ 180,128
Lake Michigan Financial Corp [Member]
Business Acquisition [Line Items]
Acquisition purchase price	$ 187,394
Goodwill acquired	101,621
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	8,600
Business Combination, Consideration Transferred, Value of Stock and Options Issued	132,900
Business Combination, Consideration Transferred, Cash Paid for Outstanding Stock	$ 54,478
Monarch Community Bancorp [Member]
Business Acquisition [Line Items]
Acquisition purchase price		$ 27,191
Goodwill acquired		5,330
Intangibles acquired		1,930
Business Combination, Consideration Transferred, Cash Paid for Outstanding Stock		$ 203
Northwestern Bancorp [Member]
Business Acquisition [Line Items]
Acquisition purchase price			$ 121,000
Goodwill acquired			60,000		$ 60,300
Intangibles acquired			$ 12,891
OAK [Member]
Business Acquisition [Line Items]
Acquisition purchase price				$ 83,700
Goodwill acquired				43,500
Intangibles acquired				$ 9,800