Borrowings and Other Financing Instruments - Borrowings and Other Financing Instruments, Long-Term Borrowings and Other Financing Instruments (Details)	6 Months Ended
Jun. 30, 2022 USD ($)
Debt Instrument [Line Items]
Term of letters of credit (in years)	1 year
Bonds [Member] \| Series Due June 1, 2032
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 300,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.10%
Bonds [Member] \| Series Due June 1, 2052
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.50%

Face (par) amount of debt instrument at time of issuance.

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Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant