Acquisition Narrative (Details) $ in Thousands				3 Months Ended			12 Months Ended
	Jul. 25, 2019 USD ($)	Jun. 14, 2019 USD ($) branch	Feb. 01, 2018 USD ($) shares	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Common stock issued in acquisition							$ 488,408	$ 7,151
Huntington National Bank
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition		Jun. 14, 2019
Business Acquisition, Name of Acquired Entity		Huntington
Business Combination, Control Obtained Description		The Corporation paid a 4% premium on acquired deposits.
New Communities | branch		13
Acquired Net Branches | branch		14
Goodwill		$ 7,000		$ 210
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			10 years
Bank Mutual [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			Feb. 01, 2018
Business Acquisition, Name of Acquired Entity			Bank Mutual
Business Combination, Control Obtained Description			the Corporation completed its acquisition of Bank Mutual in a stock transaction
Common stock issued in acquisition			$ 482,000
Consideration shares transferred | shares			0.422
Common Stock Issued During Period, Shares, Acquisitions | shares			19,500,000
Goodwill					$ 2,000	$ 6,000	$ 175,000
First Staunton Bancshares
Business Acquisition [Line Items]
Business Acquisition, Name of Acquired Entity	First Staunton
Business Acquisition, Date of Acquisition Agreement	Jul. 25, 2019
Estimated Consideration Transferred	$ 76,000