Acquisitions Purchase Accounting Fair Value Adjustments (Details) - USD ($) $ in Thousands		May. 31, 2015	Apr. 01, 2015	Oct. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Purchase Accounting Fair Value Adjustments [Line Items]
Goodwill					$ 287,393	$ 180,128
Lake Michigan Financial Corp [Member]
Purchase Accounting Fair Value Adjustments [Line Items]
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, Deferred Tax Asset, Net	[1]	3,572
Purchase Accounting Fair Value Adjustment, Deposits and Other Borrowings	[1]	(3,182)
Purchase Accounting Fair Value Adjustment, Other Assets and Liabilities, Net		(157)
Purchase Accounting Fair Value Adjustment, Premises and Equipment	[1]	(5,031)
Purchase Accounting Fair Value Adjustment, Core Deposit Intangible Asset		8,003
Net Assets Acquired After Purchase Accounting Fair Value Adjustments		85,773
Goodwill		$ 101,621
Monarch Community Bancorp [Member]
Purchase Accounting Fair Value Adjustments [Line Items]
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, Deferred Tax Asset, Net	[2]		1,826
Purchase Accounting Fair Value Adjustment, Premises and Equipment	[2]		(395)
Purchase Accounting Fair Value Adjustment, Core Deposit Intangible Asset			1,930
Purchase Accounting Fair Value Adjustment, Mortgage Servicing Rights Asset			315
Purchase Accounting, Other assets and other liabilities			37
Net Assets Acquired After Purchase Accounting Fair Value Adjustments			21,861
Goodwill			$ 5,330
Northwestern Bancorp [Member]
Purchase Accounting Fair Value Adjustments [Line Items]
Business Combination, Consideration Transferred				$ 121,000
Goodwill				$ 60,000	$ 60,300

[1] (2) Includes adjustments to the fair value as a result of additional valuation information obtained during the fourth 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.

[2] (2) Includes immaterial adjustments to the fair value as a result of additional valuation information obtained during the fourth quarter of 2015, including the corresponding tax effects.