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Interim Pension and Other Postretirement Benefits (Details) - USD ($) $ in Thousands |  | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
Mar. 01, 2018 | Mar. 31, 2018 | Mar. 31, 2017 | Mar. 31, 2018 | Mar. 31, 2017
Pension Benefits [Member] |  |  |  |  |
Components of net periodic pension cost [Abstract] |  |  |  |  |
Service Cost |  | $ 4,575 | $ 5,217 | $ 9,135 | $ 10,433
Interest Cost |  | 6,433 | 6,297 | 12,863 | 12,594
Expected return on assets |  | (6,916) | (6,994) | (13,833) | (13,988)
Amortization of prior service (credit)/cost |  | (58) | (58) | (116) | (116)
Amortization of actuarial (gain) loss |  | 3,085 | 4,249 | 6,174 | 8,498
Settlements |  | 2,415 | 0 | 2,415 | 0
Net periodic pension cost |  | $ 9,534 | $ 8,711 | $ 16,638 | $ 17,421
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost Abstract |  |  |  |  |
Discount Rate |  | 3.89% | 3.73% | 3.89% | 3.73%
Rate of compensation increase |  | 3.50% | 3.50% | 3.50% | 3.50%
Expected return on plan assets |  | 6.75% | 7.00% | 6.75% | 7.00%
Supplemental Employee Retirement Plan [Member] |  |  |  |  |
Components of net periodic pension cost [Abstract] |  |  |  |  |
Settlements |  | $ (2,400) |  |  |
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost Abstract |  |  |  |  |
Discount Rate | 4.12% | 4.12% | 3.73% | 4.12% | 3.73%
Rate of compensation increase |  | 3.50% | 3.50% | 3.50% | 3.50%
Current Year Benefit Plan Contributions [Abstract] |  |  |  |  |
Change in Net Periodic Cost, Remainder of Year |  | $ 100 |  |  |
Other Benefits [Member] |  |  |  |  |
Components of net periodic pension cost [Abstract] |  |  |  |  |
Service Cost |  | 3,019 | $ 3,109 | $ 6,039 | $ 6,218
Interest Cost |  | 2,727 | 2,670 | 5,454 | 5,340
Expected return on assets |  | (2,001) | (1,797) | (4,003) | (3,593)
Amortization of prior service (credit)/cost |  | 3 | (411) | 6 | (822)
Amortization of actuarial (gain) loss |  | (1,619) | (707) | (3,237) | (1,414)
Settlements |  | 0 | 0 | 0 | 0
Net periodic pension cost |  | $ 2,129 | $ 2,864 | $ 4,259 | $ 5,729
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost Abstract |  |  |  |  |
Discount Rate |  | 3.89% | 3.73% | 3.89% | 3.73%
Expected return on plan assets |  | 4.29% | 4.45% | 4.29% | 4.45%
Current Year Benefit Plan Contributions [Abstract] |  |  |  |  |
Contributions Actual |  |  |  | $ 7,500 |
Other Benefits [Member] | Minimum [Member] |  |  |  |  |
Current Year Benefit Plan Contributions [Abstract] |  |  |  |  |
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year |  | $ 10,000 |  | 10,000 |
Other Benefits [Member] | Maximum [Member] |  |  |  |  |
Current Year Benefit Plan Contributions [Abstract] |  |  |  |  |
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year |  | $ 20,000 |  | $ 20,000 |

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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(5) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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