Pension and Other Postretirement Benefits - Hierarchy of Fair Value of the Benefit Plan Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	$ 876,036	$ 825,869
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	40,897	78,336
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	680,798	631,543
NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	154,341	115,990
Corporate Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	394,521	407,008
Corporate Fixed Income Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	394,521	407,008
Value Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets		66,950
Growth Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets		38,119
Balanced Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets		10,921
Defined Benefit Plan, Common Collective Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	94,667
Defined Benefit Plan, Common Collective Trust [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	94,667
Mutual Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	59,674
Mutual Fund [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	59,674
Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	38,487	74,448
Common Stock [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	38,487	74,448
US Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	178,364	61,770
US Government Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	178,364	61,770
Foreign Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	61,153	48,011
Foreign Government Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	61,153	48,011
Other Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	22,544	32,971
Other Fixed Income Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	22,544	32,971
Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	26,626	85,671
Other [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	2,410	3,888
Other [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans', Fair Value of Plan Assets	$ 24,216	$ 81,783