Retirement Benefits - Net periodic pension cost recognized (Details) - Pension Plans, Defined Benefit - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 82,743	$ 76,647	$ 82,993
Interest cost	142,479	160,542	144,339
Expected return on plan assets	(266,674)	(251,072)	(258,490)
Amortization of prior service cost	5,633	6,655	6,570
Amortization of unrecognized actuarial loss	165,815	121,823	147,387
Amortization of transition obligation	18	18	18
Net periodic benefit cost	$ 130,014	$ 114,613	$ 122,817