Retirement Benefit Obligations - Summary of Changes in Fair Value of Investments Reflected as Level 3 Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Beginning balance	$ 1,367	$ 1,506
Actual return on plan assets:
Ending balance	1,389	1,367
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning balance	11	12
Actual return on plan assets:
Actual return on plan assets, Relating to assets still held at end of period	0	0
Actual return on plan assets, Relating to assets sold during the period	0	0
Purchases, sales, settlements and issuances	0	(1)
Transfers in and out of Level 3	0	0
Ending balance	$ 11	$ 11