Retirement Benefits - Fair values of pension plan assets by asset class (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Jun. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 5,455,294	$ 4,362,153
Fair Value, Inputs, Level 1, 2 and 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	341,812	201,053
Fair Value, Inputs, Level 1, 2 and 3 | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	538,118	327,122
Fair Value, Inputs, Level 1, 2 and 3 | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	152,354	8,700
Fair Value, Inputs, Level 1, 2 and 3 | Fixed income securities, Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	464,056	380,694
Fair Value, Inputs, Level 1, 2 and 3 | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	610,326	87,650
Fair Value, Inputs, Level 1, 2 and 3 | Mutual funds, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	11,406	9,085
Fair Value, Inputs, Level 1, 2 and 3 | Mutual funds, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	357	9,679
Fair Value, Inputs, Level 1, 2 and 3 | Miscellaneous
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	308,610	206,850
Quoted Prices In Active Markets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,634,467	601,712
Quoted Prices In Active Markets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	333,978	190,616
Quoted Prices In Active Markets (Level 1) | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	523,649	327,122
Quoted Prices In Active Markets (Level 1) | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	76,173	8,700
Quoted Prices In Active Markets (Level 1) | Fixed income securities, Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	118,536	1,309
Quoted Prices In Active Markets (Level 1) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	570,368	55,201
Quoted Prices In Active Markets (Level 1) | Mutual funds, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	11,406	9,085
Quoted Prices In Active Markets (Level 1) | Mutual funds, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	357	9,679
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	792,572	629,121
Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	7,834	10,437
Significant Other Observable Inputs (Level 2) | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	14,469	0
Significant Other Observable Inputs (Level 2) | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	76,181	0
Significant Other Observable Inputs (Level 2) | Fixed income securities, Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	345,520	379,385
Significant Other Observable Inputs (Level 2) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	39,958	32,449
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	308,610	206,850
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	264,346	279,849
Measured at Net Asset Value | Common/Collective trusts measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	2,626,832	2,718,445
Measured at Net Asset Value | Limited Partnerships measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 137,077	$ 133,026