Loans Narrative (Details) - USD ($) $ in Thousands		6 Months Ended		12 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Recorded Investment, loans modified in troubled debt restructuring	[1]	$ 6,370	$ 4,035
Restructured Loans Subsequently Accruing		1,000
Ytd Restructured Loans Still On Nonaccrual		5,000
Net unaccreted purchase discount		17,000		$ 20,000
Unaccreted purchase discount, performing loans		16,000		18,000
Unaccreted purchase discount, nonperforming loans		1,000		2,000
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses		233,659		238,023	$ 265,880
Bank Mutual
Financing Receivable, Allowance for Credit Loss [Line Items]
Purchased credit-impaired loans		2,000		5,000
Huntington National Bank
Financing Receivable, Allowance for Credit Loss [Line Items]
Purchased credit-impaired loans		0
Oil and Gas
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for loan losses		$ 25,000		$ 12,000	$ 27,000
Percent of Loans		3.80%		1.60%

[1] (a) Represents post-modification outstanding recorded investment.