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Financing: At-the-Market Equity Offering Program (Details) - USD ($) $ in Millions | Jun. 16, 2023 | Aug. 04, 2020
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At The Market Equity Offering Program Authorized Aggregate Value | $ 400 | $ 400

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- Definition At The Market Equity Offering Program authorized an aggregate value that the Company may, through its sales agents, offer and sell from time to time shares of its common stock. + References No definition available. + Details
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Namespace Prefix: | bkh_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant