Acquisition - Narrative (Details) $ in Thousands			12 Months Ended
	Dec. 02, 2016 USD ($) branch	Oct. 01, 2015 USD ($) branch	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Oct. 03, 2016 USD ($) branch
Business Acquisition [Line Items]
Costs related to the acquisition			$ 3,173	$ 922	$ 0
Goodwill			$ 186,483	$ 164,500
FirstMerit Bank, NA, Branch Acquisition [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	$ 121,197
Business Combination, Acquired Receivables, Gross Contractual Amount	105,627
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits	619,729
Total consideration paid	$ (476,555)
Number of Stores | branch	13
Goodwill	$ 22,047
Business Combination, Acquired Receivables, Fair Value Adjustment	$ 3,530
DCB Financial Corp [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets						$ 550,000
Business Combination, Acquired Receivables, Gross Contractual Amount						388,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits						$ 477,000
Number of Stores | branch						9
First Community Bank
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		$ 103,106
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits		90,311
Total consideration paid		14,750
Gross loans receivable acquired		62,500
Credit market adjustment of gross loans acquired		1,300
Costs related to the acquisition		$ 900
Number of Stores | branch		4
Goodwill		$ 3,070