Retirement Benefit Obligations - Schedule of Weighted-Average Asset Allocations, by Asset Category (Detail)	Jun. 30, 2019	Jun. 30, 2018
Asset Category:
Benefit plan weighted-average asset allocations	100.00%	100.00%
Equity Securities [Member]
Asset Category:
Benefit plan weighted-average asset allocations	22.00%	23.00%
Debt Securities [Member]
Asset Category:
Benefit plan weighted-average asset allocations	68.00%	65.00%
Cash And Other [Member]
Asset Category:
Benefit plan weighted-average asset allocations	10.00%	12.00%