Retirement Benefit Obligations - Schedule of Allocation of Plan Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2021
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 933	$ 1,051	$ 1,447
NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	315	391
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78	53
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	534	600
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	7	$ 10
Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	37	37
Domestic equity funds | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	37	37
Domestic equity funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Domestic equity funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Domestic equity funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94	112
International equity funds | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	46	45
International equity funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International equity funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48	67
International equity funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Domestic fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	112	106
Domestic fixed income funds | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	112	106
Domestic fixed income funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Domestic fixed income funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Domestic fixed income funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	546	666
International fixed income funds | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	102	179
International fixed income funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International fixed income funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	444	487
International fixed income funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Balanced funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	42	46
Balanced funds | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Balanced funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Balanced funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	42	46
Balanced funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	102	84
Other | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18	24
Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78	53
Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 6	$ 7