Retirement Benefits - Employee stock ownership plan (ESOP) (Details) - USD ($) $ in Thousands	12 Months Ended
Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2021
Retirement Benefits [Abstract]
Shares held by ESOP (in shares)	3,779,985	4,125,214	4,497,902
Company matching contributions	$ 104,237	$ 87,554	$ 66,249

This item represents the amount of cash contributions during the period made by the entity to the Employee Stock Ownership Plan (ESOP).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480489/718-40-50-1

Name:	us-gaap_EmployeeStockOwnershipPlanESOPCashContributionsToESOP
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration