Retirement Benefits - Fair values of pension plan assets by asset class (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 5,366,107	$ 5,455,294
Fair Value, Inputs, Level 1, 2 and 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	454,659	341,812
Fair Value, Inputs, Level 1, 2 and 3 | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	679,972	538,118
Fair Value, Inputs, Level 1, 2 and 3 | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	144,760	152,354
Fair Value, Inputs, Level 1, 2 and 3 | Fixed income securities, Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	933,191	464,056
Fair Value, Inputs, Level 1, 2 and 3 | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	809,892	610,326
Fair Value, Inputs, Level 1, 2 and 3 | Mutual funds, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	12,494	11,406
Fair Value, Inputs, Level 1, 2 and 3 | Mutual funds, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		357
Fair Value, Inputs, Level 1, 2 and 3 | Other financial instruments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	312,477	308,610
Quoted Prices In Active Markets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,824,774	1,634,467
Quoted Prices In Active Markets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	448,510	333,978
Quoted Prices In Active Markets (Level 1) | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	679,972	523,649
Quoted Prices In Active Markets (Level 1) | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	85,692	76,173
Quoted Prices In Active Markets (Level 1) | Fixed income securities, Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	28,790	118,536
Quoted Prices In Active Markets (Level 1) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	556,599	570,368
Quoted Prices In Active Markets (Level 1) | Mutual funds, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	12,494	11,406
Quoted Prices In Active Markets (Level 1) | Mutual funds, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		357
Quoted Prices In Active Markets (Level 1) | Other financial instruments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	12,717	0
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,522,671	792,572
Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	6,149	7,834
Significant Other Observable Inputs (Level 2) | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	14,469
Significant Other Observable Inputs (Level 2) | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	59,068	76,181
Significant Other Observable Inputs (Level 2) | Fixed income securities, Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	904,401	345,520
Significant Other Observable Inputs (Level 2) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	253,293	39,958
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
Significant Other Observable Inputs (Level 2) | Other financial instruments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	299,760	308,610
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
Significant Unobservable Inputs (Level 3) | Other financial instruments
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	331,215	264,346
Measured at Net Asset Value | Common/Collective trusts measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,561,752	2,626,832
Measured at Net Asset Value | Limited Partnerships measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 125,695	$ 137,077