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Retirement Benefits (Schedule of Allocation of Plan Assets, Fair Value Hierarchy) (Details) - Defined Benefit Pension Plan [Member] - USD ($) $ in Thousands | Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2018
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | $ 266,709 | $ 234,133 | $ 227,722
United States [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 201,555 | 170,556 | 165,342
Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 65,154 | 63,577 | $ 62,380
Level 1 [Member] | United States [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 201,555 | 170,556 |
Level 1 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 270 | 418 |
Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 64,884 | 63,159 |
Cash and Cash Equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1,385 | 2,986 |
Cash and Cash Equivalents | Level 1 [Member] | United States [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1,115 | 2,568 |
Cash and Cash Equivalents | Level 1 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 270 | 418 |
Debt Security, Corporate, US |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 70,492 | 64,514 |
Debt Security, Corporate, US | Level 1 [Member] | United States [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 70,492 | 64,514 |
Domestic Equity Large Cap Fund |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 65,025 | 56,829 |
Domestic Equity Large Cap Fund | Level 1 [Member] | United States [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 65,025 | 56,829 |
International Equity Large Cap Growth Fund |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 64,923 | 46,645 |
International Equity Large Cap Growth Fund | Level 1 [Member] | United States [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 64,923 | 46,645 |
Private Equity Funds Foreign Japan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 2,470 | 2,518 |
Private Equity Funds Foreign Japan | Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 2,470 | 2,518 |
Private Equity Funds Pooled Funds Foreign |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 2,135 | 2,226 |
Private Equity Funds Pooled Funds Foreign | Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 2,135 | 2,226 |
Fixed Income Funds Japan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 5,151 | 4,915 |
Fixed Income Funds Japan | Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 5,151 | 4,915 |
Fixed Income Funds Foreign |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1,734 | 1,710 |
Fixed Income Funds Foreign | Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1,734 | 1,710 |
Global Target Return Equity Bond Fund |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 13,002 | 12,488 |
Global Target Return Equity Bond Fund | Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 13,002 | 12,488 |
United Kingdom Index Linked Equity Fund |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 2,878 | 3,738 |
United Kingdom Index Linked Equity Fund | Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 2,878 | 3,738 |
Index linked international equity fund |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 5,351 | 5,438 |
Index linked international equity fund | Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 5,351 | 5,438 |
Corporate Debt Securities United Kingdom |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 18,055 | 16,737 |
Corporate Debt Securities United Kingdom | Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 18,055 | 16,737 |
Pooled funds: Index linked U.K. government securities fund [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 5,767 | 5,491 |
Pooled funds: Index linked U.K. government securities fund [Member] | Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 5,767 | 5,491 |
Pooled funds: Index linked U.K. long-term government securities fund [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 8,341 | 7,898 |
Pooled funds: Index linked U.K. long-term government securities fund [Member] | Level 2 [Member] | Foreign Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | $ 8,341 | $ 7,898 |

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