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Pension and Other Postemployment Benefits (Details 4) - OPEB - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | $ 457 | $ 410
Asset Allocation | 100.00% | 100.00%
Cash and short-term securities |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | $ 72 | $ 71
Asset Allocation | 16.00% | 17.00%
Domestic |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | $ 246 | $ 196
Asset Allocation | 54.00% | 48.00%
Government bonds |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | $ 100 | $ 107
Asset Allocation | 22.00% | 26.00%
Corporate debt securities |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | $ 34 | $ 32
Asset Allocation | 7.00% | 8.00%
Mortgaged-backed securities (non-government) |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | $ 5 | $ 4
Asset Allocation | 1.00% | 1.00%
Level 1 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | $ 246 | $ 196
Level 1 | Cash and short-term securities |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 0 | 0
Level 1 | Domestic |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 246 | 196
Level 1 | Government bonds |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 0 | 0
Level 1 | Corporate debt securities |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 0 | 0
Level 1 | Mortgaged-backed securities (non-government) |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value |  |
Level 2 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 211 | 214
Level 2 | Cash and short-term securities |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 72 | 71
Level 2 | Domestic |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 0 | 0
Level 2 | Government bonds |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 100 | 107
Level 2 | Corporate debt securities |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 34 | 32
Level 2 | Mortgaged-backed securities (non-government) |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 5 | 4
Level 3 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 0 | 0
Level 3 | Cash and short-term securities |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 0 | 0
Level 3 | Domestic |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 0 | 0
Level 3 | Government bonds |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 0 | 0
Level 3 | Corporate debt securities |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | 0 | 0
Level 3 | Mortgaged-backed securities (non-government) |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Pension investments measured at fair value | $ 0 | $ 0

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- Definition Defined Benefit Plan, Fair Value Of Plan Assets, Excluding Net Receivables (Payables), Taxes and Accrued Income + References No definition available. + Details
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- Definition Percentage of actual 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/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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