Retirement Benefits - Fair values of pension plan assets by asset class (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 3,915,889	$ 3,896,001
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	57,307	76,057
Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	447,553	416,830
Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	243,253	236,134
Fixed income securities, Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	225,929	176,135
Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	272,604	199,389
Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	176,846	306,168
Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	179,562	204,628
Common/Collective trusts, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	89,578	70,389
Common/Collective trusts, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 46,620	46,003
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	$ (36,492)	(9,000)
Quoted Prices In Active Markets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,537,904	1,592,120
Quoted Prices In Active Markets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	54,322	75,370
Quoted Prices In Active Markets (Level 1) | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	447,553	416,830
Quoted Prices In Active Markets (Level 1) | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	243,253	236,134
Quoted Prices In Active Markets (Level 1) | Fixed income securities, Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	115,534	91,982
Quoted Prices In Active Markets (Level 1) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	184,636	144,616
Quoted Prices In Active Markets (Level 1) | Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	176,846	306,168
Quoted Prices In Active Markets (Level 1) | Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	179,562	204,628
Quoted Prices In Active Markets (Level 1) | Common/Collective trusts, Equity funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	89,578	70,389
Quoted Prices In Active Markets (Level 1) | Common/Collective trusts, Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	46,620	46,003
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	164,856	130,613
Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	2,985	687
Significant Other Observable Inputs (Level 2) | Equity securities, U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0
Significant Other Observable Inputs (Level 2) | Equity securities, Non-U.S. based companies
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets		0
Significant Other Observable Inputs (Level 2) | Fixed income securities, Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	110,395	84,153
Significant Other Observable Inputs (Level 2) | Fixed income securities, Government issued securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	87,968	54,773
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	0
Significant Other Observable Inputs (Level 2) | Miscellaneous
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	(36,492)	(9,000)
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	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	232,050	233,234
Measured at Net Asset Value | Common/Collective trusts
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,737,543	1,677,942
Measured at Net Asset Value | Limited Partnerships measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	243,536	262,092
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	3,915,889	3,896,001	$ 3,307,047
Company stock included in U.S. based company equity securities	$ 207,202	$ 212,480