Retirement benefits (Tables)

6 Months Ended

Dec. 31, 2020

Retirement Benefits [Abstract]

Schedule of net pension benefit expense

Net pension benefit expense recognized included the following components:

	Three Months Ended				Six Months Ended
	December 31,				December 31,
	2020		2019		2020		2019
Service cost	$	19,389	$	21,449	$	42,199	$	40,998
Interest cost	25,755		35,851		51,172		69,844
Expected return on plan assets	(66,807)		(66,883)		(133,209)		(130,778)
Amortization of prior service cost	1,446		1,309		2,289		2,818
Amortization of net actuarial loss	52,829		42,779		105,160		82,340
Amortization of initial net obligation	4		5		9		9
Net pension benefit expense	$	32,616	$	34,510	$	67,620	$	65,231