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Investment Securities (Details Textual) - USD ($) $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2017
Business Acquisition [Line Items] |  |  |
Debt Securities, Available-for-sale, Sold at Par Value | $ 40 |  |
Investment Securities (Textuals) [Abstract] |  |  |
Debt Securities, Available-for-sale, Sold at Par Value | 40 |  |
Debt Securities, Held-to-maturity, Sold, Amount |  | $ 16 |
Federal Home Loan Bank Stock | 173 |  | $ 89
Federal Reserve Bank Stock | 76 |  | $ 76
Bank Mutual [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Debt Securities, Available-for-sale, Sold at Par Value | 453 |  |
Investment Securities (Textuals) [Abstract] |  |  |
Debt Securities, Available-for-sale, Sold at Par Value | $ 453 |  |

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- Definition Investment securities. + 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. + Details
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- Definition Amount of investment in debt security, measured at amortized cost, sold. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27405-111563 + Details
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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 + Details
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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 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 + Details
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- Details
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