Acquisitions Purchase Accounting Fair Value Adjustments (Details) - USD ($) $ / shares in Units, $ in Thousands		May. 31, 2015	Apr. 01, 2015	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Purchase Accounting Fair Value Adjustments [Line Items]
Goodwill				$ 286,454	$ 180,128	$ 120,164
Monarch Community Bancorp [Member]
Purchase Accounting Fair Value Adjustments [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares			860,575
Business Combination, Consideration Transferred, Value of Stock Issued			$ 26,988
Business Combination, Consideration Transferred, Cash Paid for Outstanding Stock			203
Business Combination, Consideration Transferred			27,191
Net Assets Acquired, Acquiree Shareholders Equity			15,270
Purchase Accounting Fair Value Adjustment, Loans			(7,150)
Purchase Accounting Fair Value Adjustment, Allowance for Loan Losses			2,128
Business Combination, Fair Value Adjustment, Deferred Tax Asset NOL			7,900
Purchase Accounting Fair Value Adjustment, Premises and Equipment			(370)
Purchase Accounting Fair Value Adjustment, Core Deposit Intangible Asset			1,930
Purchase Accounting Fair Value Adjustment, Mortgage Servicing Rights Asset			315
Purchase Accounting Fair Value Adjustment, Deferred Tax Asset, Net	[1]		1,817
Purchase Accounting Fair Value Adjustment, Other Assets and Liabilities, Net			37
Net Assets Acquired After Purchase Accounting Fair Value Adjustments			21,877
Goodwill			$ 5,314
Business Acquisition, Price Per Share of Common Stock Issued			$ 31.36
Lake Michigan Financial Corp [Member]
Purchase Accounting Fair Value Adjustments [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares		4,322,101
Business Combination, Consideration Transferred, Value of Stock Issued		$ 130,916
Business Combination, Consideration Transferred, Value of Stock Options		2,000
Business Combination, Consideration Transferred, Cash Paid for Outstanding Stock		54,478
Business Combination, Consideration Transferred		187,394
Net Assets Acquired, Acquiree Shareholders Equity		89,280
Purchase Accounting Fair Value Adjustment, Loans		(22,600)
Purchase Accounting Fair Value Adjustment, Allowance for Loan Losses		15,888
Purchase Accounting Fair Value Adjustment, Premises and Equipment	[2]	(4,022)
Purchase Accounting Fair Value Adjustment, Core Deposit Intangible Asset	[2]	8,003
Purchase Accounting Fair Value Adjustment, Deferred Tax Asset, Net	[2]	3,172
Purchase Accounting Fair Value Adjustment, Deposits and Other Borrowings		(3,048)
Purchase Accounting Fair Value Adjustment, Other Assets and Liabilities, Net	[2]	157
Net Assets Acquired After Purchase Accounting Fair Value Adjustments		86,516
Goodwill		$ 100,878
Business Acquisition, Price Per Share of Common Stock Issued		$ 30.29

[1] Includes adjustments to the fair value as a result of additional valuation information obtained during the third quarter of 2015. A summary of these adjustments is included in the section "Allocation of Purchase Price" within this footnote.

[2] Includes adjustments to the fair value as a result of additional valuation information obtained during the third quarter of 2015, including the corresponding tax effects. A summary of these adjustments is included in the section "Allocation of Purchase Price" within this footnote.