Retirement Benefit Obligations - Schedule of Weighted-Average Asset Allocations, by Asset Category (Detail)	Jun. 30, 2021	Jun. 30, 2020
Asset Category:
Benefit plan weighted-average asset allocations	100.00%	100.00%
Equity securities
Asset Category:
Benefit plan weighted-average asset allocations	19.00%	20.00%
Debt securities
Asset Category:
Benefit plan weighted-average asset allocations	73.00%	68.00%
Cash and other
Asset Category:
Benefit plan weighted-average asset allocations	8.00%	12.00%