Retirement Benefits - Fair values of pension plan assets by asset class (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 4,244,969	$ 3,915,889
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	111,520	57,307
Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	226,027	447,553
Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	16,385	243,253
Fixed income securities, Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	701,842	225,929
Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	528,394	272,604
Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	266,240	176,846
Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	183,732	179,562
Common/Collective trusts, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 84,790	89,578
Common/Collective trusts, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		46,620
Common/Collective trusts
Defined Benefit Plan Disclosure [Line Items]
Investments valued using a net asset value per share, redemption notice period (in days)	60 days
Limited Partnerships measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Investments valued using a net asset value per share, redemption notice period (in days)	95 days
Miscellaneous
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ (291,741)	(36,492)
Quoted Prices In Active Markets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,399,742	1,537,904
Quoted Prices In Active Markets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	117,823	54,322
Quoted Prices In Active Markets (Level 1) | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	226,027	447,553
Quoted Prices In Active Markets (Level 1) | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	16,385	243,253
Quoted Prices In Active Markets (Level 1) | Fixed income securities, Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	137,227	115,534
Quoted Prices In Active Markets (Level 1) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	367,518	184,636
Quoted Prices In Active Markets (Level 1) | Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	266,240	176,846
Quoted Prices In Active Markets (Level 1) | Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	183,732	179,562
Quoted Prices In Active Markets (Level 1) | Common/Collective trusts, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	84,790	89,578
Quoted Prices In Active Markets (Level 1) | Common/Collective trusts, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		46,620
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	427,447	164,856
Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	(6,303)	2,985
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 bonds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	564,615	110,395
Significant Other Observable Inputs (Level 2) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	160,876	87,968
Significant Other Observable Inputs (Level 2) | Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Other Observable Inputs (Level 2) | Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Other Observable Inputs (Level 2) | Common/Collective trusts, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Other Observable Inputs (Level 2) | Common/Collective trusts, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0
Significant Other Observable Inputs (Level 2) | Miscellaneous
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	(291,741)	(36,492)
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 bonds
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) | Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Common/Collective trusts, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Significant Unobservable Inputs (Level 3) | Common/Collective trusts, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		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
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	304,504	232,050
Measured at Net Asset Value | Common/Collective trusts
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,872,473	1,737,543
Measured at Net Asset Value | Limited Partnerships measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	240,803	243,536
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	4,244,969	3,915,889	$ 3,896,001
Company stock included in U.S. based company equity securities	$ 226,027	$ 207,202