Retirement benefits (Tables)

6 Months Ended

Dec. 31, 2022

Retirement Benefits [Abstract]

Net pension benefit expense

Net pension benefit expense recognized included the following components:

	Three Months Ended				Six Months Ended
	December 31,				December 31,
	2022		2021		2022		2021
Service cost	$	13,682	$	18,699	$	27,935	$	39,361
Interest cost	61,084		27,559		107,435		54,988
Expected return on plan assets	(82,213)		(67,135)		(148,558)		(134,463)
Amortization of prior service cost	242		1,122		452		2,056
Amortization of net actuarial loss	6,839		41,085		13,282		78,616
Amortization of initial net obligation	—		2		—		4
Net pension benefit expense	$	(366)	$	21,332	$	546	$	40,562