Retirement Benefits - Fair values of pension plan assets by asset class (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Jun. 30, 2021
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 4,362,153	$ 5,305,577
Fair Value, Inputs, Level 1, 2 and 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	201,053	248,525
Fair Value, Inputs, Level 1, 2 and 3 | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	327,122	408,301
Fair Value, Inputs, Level 1, 2 and 3 | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	8,700	12,834
Fair Value, Inputs, Level 1, 2 and 3 | Fixed income securities, Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	380,694	531,497
Fair Value, Inputs, Level 1, 2 and 3 | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	87,650	151,458
Fair Value, Inputs, Level 1, 2 and 3 | Mutual funds, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	9,085	6,768
Fair Value, Inputs, Level 1, 2 and 3 | Mutual funds, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	9,679	6,506
Fair Value, Inputs, Level 1, 2 and 3 | Miscellaneous
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	206,850	283,059
Quoted Prices In Active Markets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	601,712	782,437
Quoted Prices In Active Markets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	190,616	241,421
Quoted Prices In Active Markets (Level 1) | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	327,122	408,301
Quoted Prices In Active Markets (Level 1) | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	8,700	12,834
Quoted Prices In Active Markets (Level 1) | Fixed income securities, Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,309	1,440
Quoted Prices In Active Markets (Level 1) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	55,201	105,167
Quoted Prices In Active Markets (Level 1) | Mutual funds, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	9,085	6,768
Quoted Prices In Active Markets (Level 1) | Mutual funds, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	9,679	6,506
Quoted Prices In Active Markets (Level 1) | Miscellaneous
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	629,121	866,511
Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	10,437	7,104
Significant Other Observable Inputs (Level 2) | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Other Observable Inputs (Level 2) | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Other Observable Inputs (Level 2) | Fixed income securities, Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	379,385	530,057
Significant Other Observable Inputs (Level 2) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	32,449	46,291
Significant Other Observable Inputs (Level 2) | Mutual funds, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Other Observable Inputs (Level 2) | Mutual funds, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Other Observable Inputs (Level 2) | Miscellaneous
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	206,850	283,059
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Fixed income securities, Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Mutual funds, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Mutual funds, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Miscellaneous
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Measured at Net Asset Value | Mutual funds measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	279,849	368,340
Measured at Net Asset Value | Common/Collective trusts measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	2,718,445	3,161,683
Measured at Net Asset Value | Limited Partnerships measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 133,026	$ 126,606