XML 48 R37.htm IDEA: XBRL DOCUMENT
v3.20.2

Note 3 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Impaired Loans, Average Investment and Interest Income (Details) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Dec. 31, 2019
Average recorded investment in impaired loans(1) | [1] | $ 5,227 | $ 6,729 |  | $ 5,359 | [2]
Interest income recognized on impaired loans, after designation as impaired |  | 49 | 144 |  | 171 |
Investor Owned Residential Real Estate [Member] | Consumer Real Estate Portfolio Segment [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) | [1] | 245 | 432 |  | 439 | [2]
Interest income recognized on impaired loans, after designation as impaired | [1] | 11 | 14 |  | 17 |
Equity Lines [Member] | Consumer Real Estate Portfolio Segment [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) |  |  | 97 | [1] | 98 |
Interest income recognized on impaired loans, after designation as impaired |  |  | 5 | [1] | 6 |
Closed End First Liens [Member] | Consumer Real Estate Portfolio Segment [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) | [1] |  | 990 |  |  |
Interest income recognized on impaired loans, after designation as impaired | [1] |  | 10 |  |  |
Closed End Junior Liens [Member] | Consumer Real Estate Portfolio Segment [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) | [1] |  | 137 |  |  |
Interest income recognized on impaired loans, after designation as impaired | [1] |  | 6 |  |  |
Closed End Junior Liens [Member] | Consumer Real Estate Portfolio Segment [Member] | Financing Receivables 30 to 89 Days Past Due [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) | [3] |  |  |  | 225 |
Closed End Junior Liens [Member] | Consumer Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) | [3] |  |  |  | 11 |
Commercial Real Estate, Owner Occupied [Member] | Commercial Real Estate Portfolio Segment [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) | [1] | 858 | 1,174 |  | 913 | [2]
Interest income recognized on impaired loans, after designation as impaired | [1] | 16 | 39 |  | 41 |
Commercial Real Estate Other [Member] | Commercial Real Estate Portfolio Segment [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) | [1] | 3,223 | 2,451 |  | 2,435 | [2]
Interest income recognized on impaired loans, after designation as impaired | [1] |  |  |  | 59 |
Multifamily Real Estate [Member] | Commercial Real Estate Portfolio Segment [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) | [1] |  | 463 |  | 284 | [2]
Interest income recognized on impaired loans, after designation as impaired | [1] |  | 9 |  | 12 |
Commercial and Industrial [Member] | Commercial Non Real Estate Segment [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) | [1] | 897 | 976 |  | 962 | [2]
Interest income recognized on impaired loans, after designation as impaired | [1] | 17 | 18 |  | 25 |
Automobile Loan [Member] | Consumer Non Real Estate Portfolio Segment [Member] |  |  |  |  |  |
Average recorded investment in impaired loans(1) | [1] | $ 4 | $ 9 |  | $ 3 | [2]
[1] | Only classes with impaired loans are shown.
[2] | Recorded investment is net of charge-offs and interest paid while a loan is in nonaccrual status.
[3] | Only classes with past-due or nonaccrual loans are shown.

X
- Definition Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5212-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5258-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nksh_InvestorOwnedResidentialRealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=nksh_ConsumerRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nksh_EquityLinesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nksh_ClosedEndFirstLiensMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nksh_ClosedEndJuniorLiensMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=nksh_FinancingReceivables30To89DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nksh_CommercialRealEstateOwnerOccupiedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nksh_CommercialRealEstateOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nksh_MultifamilyRealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nksh_CommercialAndIndustrialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=nksh_CommercialNonRealEstateSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_AutomobileLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=nksh_ConsumerNonRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |