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EMPLOYEE BENEFIT PLANS - NET PENSION EXPENSE (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Plan Assets, Contributions by Employer |  |  | $ 65 |
Qualified Defined Benefit [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Service cost | $ 11 | $ 12 | 32 | $ 36
Interest cost | 23 | 20 | 67 | 59
Expected return on assets | (24) | (27) | (71) | (80)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | (1) | (1) | (1) | (1)
Recognized actuarial loss (gain) | 9 | 9 | 27 | 25
Wages and Benefits [Member] | Qualified Defined Benefit [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Net pension expense | 11 | 12 | 32 | 36
Nonoperating Income (Expense) [Member] | Qualified Defined Benefit [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |
Net pension expense | $ 7 | $ 1 | $ 22 | $ 3

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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/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 (h)(5) -URI http://asc.fasb.org/extlink&oid=108410482&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 6 -Subparagraph (a)(5) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920 + Details
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