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Income Taxes - Additional Information (Detail) - USD ($) | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Income Taxes [Line Items] |  |
Bad debt reserves, created for tax purposes | $ 52,800,000 |
Unrecognized deferred income tax liability | 13,000,000.0 |
Valuation allowance recorded | 0 | $ 0
Federal tax credits | 1,332,000 | 0
Federal |  |
Income Taxes [Line Items] |  |
Operating loss carryforwards | 36,700,000 | 52,400,000
State |  |
Income Taxes [Line Items] |  |
Operating loss carryforwards | 129,100,000 | $ 132,200,000
AnchorBank WI |  |
Income Taxes [Line Items] |  |
Bad debt reserves, created for tax purposes | 50,900,000 |
Lafayette Savings Bank |  |
Income Taxes [Line Items] |  |
Bad debt reserves, created for tax purposes | $ 1,900,000 |

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- Definition Amount of bad debt reserves for tax purposes of qualified lenders excluded in calculating deferred taxes. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 740 -Section 25 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109255323&loc=d3e66323-112835 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 740 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6479915&loc=d3e66715-112838 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 25 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=121573983&loc=d3e28200-109314 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 740 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6487024&loc=d3e29054-158556 + Details
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- Definition Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319 + Details
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