Pension and Other Postretirement Benefits - Hierarchy of Fair Value of the Benefit Plan Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	$ 890,104	$ 876,036
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	43,777	40,897
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	707,543	680,798
NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	138,784	154,341
Corporate Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	443,948	394,521
Corporate Fixed Income Securities [Member] \| Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	443,948	394,521
Value Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	48,446	59,674
Balanced Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	90,338	94,667
Balanced Funds [Member] \| NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	90,338	94,667
Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	42,670	38,487
Common Stock [Member] \| Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	42,670	38,487
US Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	149,514	178,364
US Government Securities [Member] \| Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	149,514	178,364
Foreign Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	57,253	61,153
Foreign Government Securities [Member] \| Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	57,253	61,153
Other Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	21,107	22,544
Other Fixed Income Securities [Member] \| Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	21,107	22,544
Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	36,828	26,626
Other [Member] \| Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	1,107	2,410
Other [Member] \| Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	$ 35,721	$ 24,216