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Employee Benefit Plans (Target and Actual Asset Allocations) (Details) | Dec. 31, 2018 | Dec. 31, 2017
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Master Trust [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 100.00% | 100.00%
Target allocation | 100.00% |
Master Trust [Member] | US Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 11.00% | 11.00%
Target allocation | 10.00% |
Master Trust [Member] | Non US Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 8.00% | 8.00%
Target allocation | 8.00% |
Master Trust [Member] | Global Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 10.00% | 10.00%
Target allocation | 10.00% |
Master Trust [Member] | Global Private Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 2.00% | 2.00%
Target allocation | 3.00% |
Master Trust [Member] | Debt Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 63.00% | 63.00%
Target allocation | 63.00% |
Master Trust [Member] | Hedge Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 2.00% | 2.00%
Target allocation | 2.00% |
Master Trust [Member] | Real Estate and Cash [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 2.00% | 2.00%
Target allocation | 2.00% |
Master Trust [Member] | Other Global Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 2.00% | 2.00%
Target allocation | 2.00% |
OPEB [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 100.00% | 100.00%
Target allocation | 100.00% |
OPEB [Member] | US Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 43.00% | 41.00%
Target allocation | 32.00% |
OPEB [Member] | Non US Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 8.00% | 8.00%
Target allocation | 6.00% |
OPEB [Member] | Debt Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 40.00% | 36.00%
Target allocation | 45.00% |
OPEB [Member] | Real Estate [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 2.00% | 2.00%
Target allocation | 2.00% |
OPEB [Member] | Cash [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocation | 7.00% | 13.00%
Target allocation | 15.00% |

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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/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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