XML 66 R54.htm IDEA: XBRL DOCUMENT
v3.21.1

Income Taxes: Winter Storm Uri (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Regulatory assets | $ 802,257 | $ 278,258
Deferred income tax liabilities, net | 428,127 | $ 408,624
Winter Storm Uri |  |
Regulatory assets | 558,825 |
Deferred income tax liabilities, net | $ 132,000 |

X
- Definition Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences with jurisdictional netting. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=120406818&loc=d3e31931-109318 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=120406818&loc=d3e31917-109318 + Details
Name: | us-gaap_DeferredIncomeTaxLiabilitiesNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
Name: | us-gaap_RegulatoryAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_UnusualOrInfrequentItemAxis=bkh_WinterStormUriMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |