Retirement and Postretirement Employee Benefit Plans - Schedule of Employee Pension Plans Investments at Fair Value (Details) - Employee Pension Plan - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Derivatives, Fair Value [Line Items]
Total investments	$ 479,025	$ 596,806	$ 528,881
Fair Value, Recurring
Derivatives, Fair Value [Line Items]
Total investments	476,642	594,730
Fair Value, Recurring | Fair Value, Inputs, Level 1, 2 and 3
Derivatives, Fair Value [Line Items]
Total investments	318,420	372,861
Fair Value, Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Common stocks
Derivatives, Fair Value [Line Items]
Total investments	210,325	239,166
Fair Value, Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Money market funds
Derivatives, Fair Value [Line Items]
Total investments	14,490	7,060
Fair Value, Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Registered investment companies
Derivatives, Fair Value [Line Items]
Total investments	53,401	74,236
Fair Value, Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Mortgage-backed securities
Derivatives, Fair Value [Line Items]
Total investments	14,175	14,048
Fair Value, Recurring | Fair Value, Inputs, Level 1, 2 and 3 | U.S. treasuries
Derivatives, Fair Value [Line Items]
Total investments	3,709	7,517
Fair Value, Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Corporate bonds
Derivatives, Fair Value [Line Items]
Total investments	22,320	30,834
Fair Value, Recurring | Level 1
Derivatives, Fair Value [Line Items]
Total investments	267,407	320,885
Fair Value, Recurring | Level 1 | Common stocks
Derivatives, Fair Value [Line Items]
Total investments	210,325	239,166
Fair Value, Recurring | Level 1 | Money market funds
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 1 | Registered investment companies
Derivatives, Fair Value [Line Items]
Total investments	53,401	74,236
Fair Value, Recurring | Level 1 | Mortgage-backed securities
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 1 | U.S. treasuries
Derivatives, Fair Value [Line Items]
Total investments	3,681	7,483
Fair Value, Recurring | Level 1 | Corporate bonds
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 2
Derivatives, Fair Value [Line Items]
Total investments	51,013	51,976
Fair Value, Recurring | Level 2 | Common stocks
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 2 | Money market funds
Derivatives, Fair Value [Line Items]
Total investments	14,490	7,060
Fair Value, Recurring | Level 2 | Registered investment companies
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 2 | Mortgage-backed securities
Derivatives, Fair Value [Line Items]
Total investments	14,175	14,048
Fair Value, Recurring | Level 2 | U.S. treasuries
Derivatives, Fair Value [Line Items]
Total investments	28	34
Fair Value, Recurring | Level 2 | Corporate bonds
Derivatives, Fair Value [Line Items]
Total investments	22,320	30,834
Fair Value, Recurring | Level 3
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 3 | Common stocks
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 3 | Money market funds
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 3 | Registered investment companies
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 3 | Mortgage-backed securities
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 3 | U.S. treasuries
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Level 3 | Corporate bonds
Derivatives, Fair Value [Line Items]
Total investments	0	0
Fair Value, Recurring | Fair Value Measured at Net Asset Value Per Share | Common/collective trusts
Derivatives, Fair Value [Line Items]
Total investments	86,891	121,570
Fair Value, Recurring | Fair Value Measured at Net Asset Value Per Share | Limited partnerships
Derivatives, Fair Value [Line Items]
Total investments	$ 71,331	$ 100,299