Investment Securities (Details Textual) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
Feb. 01, 2018	Mar. 31, 2019	Dec. 31, 2018
Investment Securities (Textuals) [Abstract]
Available-for-sale Securities, Equity Securities		$ 2,000	$ 2,000
Visa Restricted Stock Owned		119
Federal Home Loan Bank Stock		$ 139,000	173,000
Federal Reserve Bank Stock		77,000	77,000
Bank Mutual
Business Acquisition [Line Items]
Debt Securities, Available-for-sale, Sold at Par Value	$ 453,000
Investment Securities Class
Investment Securities (Textuals) [Abstract]
Pledged Financial Instruments, Not Separately Reported, Securities		$ 3,600,000	$ 3,000,000

Investment securities.

No definition available.

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- Definition

Visa Restricted Stock Owned

+ References

No definition available.

+ Details

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- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

No definition available.

+ Details

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with interest rate reset through auction process, sold at par value.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 325
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809

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- Definition

Federal Reserve Bank stock represents an equity interest in the Federal Reserve Bank. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

+ Details

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- Definition

Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

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