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Retirement Plans (Strategic Allocation of Plan Assets) (Details) | Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015
--- | --- | --- | ---
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 100.00% |  |
Actual asset allocations |  |  |
Actual plan asset allocations | 100.00% | 100.00% | 100.00%
Equity Securities [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 20.00% | 30.00% | 40.00%
Actual asset allocations |  |  |
Actual plan asset allocations | 21.00% | 29.00% | 39.00%
Large Capitalization Stocks [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 12.00% |  |
Small Capitalization Stocks [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 3.00% |  |
International Stocks [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 5.00% |  |
Fixed Income Securities [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 80.00% |  |
Fixed Income Funds [Member] |  |  |
Actual asset allocations |  |  |
Actual plan asset allocations | 78.00% | 69.00% | 60.00%
Cash and Cash Equivalents [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 0.00% |  |
Actual asset allocations |  |  |
Actual plan asset allocations | 1.00% | 2.00% | 1.00%
Minimum [Member] | Equity Securities [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 15.00% |  |
Minimum [Member] | Fixed Income Funds [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage |  |  |
Minimum [Member] | Cash and Cash Equivalents [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 0.00% |  |
Maximum [Member] | Fixed Income Funds [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 80.00% |  |
Maximum [Member] | Cash and Cash Equivalents [Member] |  |  |
Strategic asset allocation |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 5.00% |  |

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- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one 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 (d)(5)(i) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2446-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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