Fair value measurement recurring basis (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Jun. 30, 2023
Fair Value Disclosures [Abstract]
Trading Securities at Fair Value	$ 2	$ 1
Interest Rate Cash Flow Hedge Asset at Fair Value	67	62
Interest Rate Cash Flow Hedge Liability at Fair Value		62
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities at Fair Value	2	1
Interest Rate Cash Flow Hedge Asset at Fair Value	67	62
Interest Rate Cash Flow Hedge Liability at Fair Value		62
Fair Value, Inputs, Level 1 [Member]
Fair Value Disclosures [Abstract]
Trading Securities at Fair Value	2	1
Interest Rate Cash Flow Hedge Asset at Fair Value	0	0
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities at Fair Value	2	1
Interest Rate Cash Flow Hedge Asset at Fair Value	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value Disclosures [Abstract]
Trading Securities at Fair Value	0	0
Interest Rate Cash Flow Hedge Asset at Fair Value	67	62
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities at Fair Value	0	0
Interest Rate Cash Flow Hedge Asset at Fair Value	67	62
Fair Value, Inputs, Level 3 [Member]
Fair Value Disclosures [Abstract]
Trading Securities at Fair Value	0	0
Interest Rate Cash Flow Hedge Asset at Fair Value	0	0
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading Securities at Fair Value	0	0
Interest Rate Cash Flow Hedge Asset at Fair Value	$ 0	$ 0

participant-directed stock and bond mutual funds

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Fair value as of the balance sheet date of all interest rate derivative assets designated as cash flow hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4B

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Fair value as of the balance sheet date of all interest rate derivative liabilities designated as cash flow hedging instruments.

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