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Financing: Revolving Credit Facility and CP Program (Details) $ in Thousands		9 Months Ended
	Jul. 19, 2021 USD ($) credit_extension	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Line of Credit Facility, Maximum Borrowing Capacity	$ 750,000
Net borrowings (payments) of Revolving Credit Facility and CP Program		$ 98,485	$ (265,180)
Commercial Paper
Short-term interest rate		0.19%
Revolving Credit Facility
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,000,000
Number Of One Year Extension Options | credit_extension	2
Debt Instrument, Term	1 year
Line of Credit Facility, Commitment Fee Percentage	0.175%
Revolving Credit Facility | Base Rate
Line of Credit Facility, Interest Rate at Period End	0.125%
Revolving Credit Facility | Eurodollar
Line of Credit Facility, Interest Rate at Period End	1.125%
Revolving Credit Facility | Letter of Credit
Line of Credit Facility, Interest Rate at Period End	1.125%

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- Definition

Net (payments) borrowings of Revolving Credit Facility and Commercial Paper Program

+ References

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+ Details

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- Definition

Number Of One Year Extension Options

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

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- Definition

The effective interest rate at the end of the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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- Definition

Weighted average interest rate of short-term debt outstanding calculated at point in time.

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