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Employee Benefit Plans - Schedule of Allocation of Plan Assets (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
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Defined Benefit Plan Disclosure [Line Items] |  |
Amount | $ 3,000 | $ 2,825
Percent of Total Assets | 100.00% | 100.00%
Growth-Oriented |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Amount | $ 1,816 | $ 2,027
Percent of Total Assets | 61.00% | 72.00%
Equity |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Amount | $ 1,324 | $ 1,772
Percent of Total Assets | 44.00% | 63.00%
Fixed Income |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Amount | $ 271 | $ 229
Percent of Total Assets | 9.00% | 8.00%
Cash and Cash Equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Amount | $ 221 | $ 26
Percent of Total Assets | 8.00% | 1.00%
Immunizing |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Amount | $ 1,184 | $ 798
Percent of Total Assets | 39.00% | 28.00%
Fixed Income |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Amount | $ 1,018 | $ 595
Percent of Total Assets | 34.00% | 21.00%
Cash and Cash Equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Amount | $ 166 | $ 203
Percent of Total Assets | 5.00% | 7.00%

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- Definition Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 4: 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=118257860&loc=d3e4179-114921 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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