Capital - Additional Information (Detail) $ / shares in Units, $ in Thousands	12 Months Ended	48 Months Ended
	Dec. 31, 2016 program $ / shares shares	Jun. 30, 2016 $ / shares shares	Dec. 02, 2016 USD ($) branch	Oct. 03, 2016 USD ($) branch	Feb. 17, 2016 shares	Jan. 27, 2015 shares	Jan. 28, 2014 shares	Jan. 29, 2013 shares	Jun. 19, 2012 USD ($)
Announcement of common stock repurchase program									$ 50,000
Number of shares authorized to be repurchased | shares					25,000,000.0	25,000,000.0	25,000,000.0	25,000,000.0
Number of repurchase programs | program	4
Stock repurchased (in shares) | shares	45,612	16,665,735
Average price per share | $ / shares	$ 8.46	$ 7.55
FirstMerit Bank, NA, Branch Acquisition [Member]
Business Combination, Acquired Receivables, Gross Contractual Amount			$ 105,627
Number of Stores | branch			13
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			$ 121,197
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits			$ 619,729
DCB Financial Corp [Member]
Business Combination, Acquired Receivables, Gross Contractual Amount				$ 388,000
Number of Stores | branch				9
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets				$ 550,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits				$ 477,000