Basis of Presentation and Significant Accounting Policies (Details) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2017 Bank	Dec. 31, 2016 USD ($)
Accounting Policies [Abstract]
Number of banks through which company operates (in bank) | Bank		1
Number of regional banking units Chemical Bank operates through (in bank) | Bank		7
Business Acquisition
Cumulative effect adjustment of change in accounting policy, net of tax impact	[1]		$ 3,659
Retained earnings
Business Acquisition
Cumulative effect adjustment of change in accounting policy, net of tax impact	[1]		3,659
New Accounting Pronouncement, Early Adoption, Effect
Business Acquisition
Tax benefits in excess of compensation costs on share-based payments			$ 2,200

[1] Refer to Note 1, Basis of Presentation and Significant Accounting Policies and Note 8, Loan Servicing Rights, for further details on the changes in accounting policy.