Retirement Benefits - Net periodic pension cost recognized (Details) - Pension Plans, Defined Benefit - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 82,993	$ 94,356	$ 94,650
Interest cost	144,339	126,131	181,469
Special termination cost	0	0	7,088
Settlement cost	0	0	5,102
Expected return on plan assets	(258,490)	(239,537)	(221,629)
Amortization of prior service cost	6,570	8,116	7,470
Amortization of unrecognized actuarial loss	147,387	212,433	170,407
Amortization of initial net obligation	18	18	17
Net periodic benefit cost	$ 122,817	$ 201,517	$ 244,574