Other Intangible Assets (Textual) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 31, 2015	Apr. 01, 2015	Oct. 31, 2014	Dec. 07, 2012
Finite-Lived Intangible Assets [Line Items]
Loans serviced for others that have servicing rights capitalized		$ 2,082,899	$ 2,093,140
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Impairment valuation allowance	[1]	0	200	$ 0
Core deposit intangible assets [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
2016		4,400
2017		3,800
2018		3,600
2019		3,400
2020		2,900
Thereafter		8,600
Mortgage servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite Lived Intangible Asset Additions		1,476	1,075	$ 1,528
Lake Michigan Financial Corp [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Finite-Lived Noncompete Agreements, Gross					$ 600
Monarch Community Bancorp [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Intangibles acquired						$ 1,930
Monarch Community Bancorp [Member] | Mortgage servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite Lived Intangible Asset Additions		1,300
Northwestern Bancorp [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Intangibles acquired							$ 12,891
Northwestern Bancorp [Member] | Mortgage servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite Lived Intangible Asset Additions			9,200
Independent Bank [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Intangibles acquired								$ 5,600
Independent Bank [Member] | Core deposit intangible assets [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Intangibles acquired								$ 5,600
Originated Portfolio Segment [Member]
Finite-Lived Intangible Assets [Line Items]
Loans serviced for others that have servicing rights capitalized		$ 888,000	$ 881,000
Originated Portfolio Segment [Member] | Weighted Average [Member] | Mortgage servicing rights [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Coupon rate (percent)		4.20%	4.28%
Discount rate (percent)		8.50%	8.50%
Prepayment speed rate (percent)		11.70%	13.60%
Acquired Portfolio Segment [Member]
Finite-Lived Intangible Assets [Line Items]
Loans serviced for others that have servicing rights capitalized		$ 1,200,000	$ 1,210,000
Acquired Portfolio Segment [Member] | Weighted Average [Member] | Mortgage servicing rights [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Coupon rate (percent)		4.07%	4.08%
Discount rate (percent)		10.10%	10.10%
Prepayment speed rate (percent)		10.41%	11.70%

[1] MSRs are stratified into servicing assets originated by the Corporation and those acquired in acquisitions of other institutions and further stratified into relatively homogeneous pools based on products with similar characteristics. The MSR impairment valuation allowance recorded at December 31, 2014 related to impairment within certain pools attributable to the Corporation's servicing portfolio that was acquired in the Northwestern transaction.