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EMPLOYEE RETIREMENT PLANS - Qualified Defined-benefit Pension Plan Assets at Fair Value by Level within the Fair Value Hierarchy (Details) - Qualified - USD ($) | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Fair Value |  |  |
Private equity funds | $ 670,000,000 | $ 695,000,000 | $ 717,000,000
Defined Benefit Plan, Net Asset Value of Plan Assets | 376,000,000 | 259,000,000 |
UNITED STATES | Common And Preferred Stock [Member] |  |  |
Fair Value |  |  |
Private equity funds | 102,000,000 | 191,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 21,000,000 | 47,000,000 |
UNITED STATES | Private Equity And Hedge Funds [Member] |  |  |
Fair Value |  |  |
Private equity funds | 32,000,000 | 36,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 0 | 0 |
UNITED STATES | Corporate Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 136,000,000 | 57,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 102,000,000 | 0 |
UNITED STATES | US Treasury and Government [Member] |  |  |
Fair Value |  |  |
Private equity funds | 132,000,000 | 53,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 130,000,000 | 31,000,000 |
UNITED STATES | Common Collective Trust Fund [Member] |  |  |
Fair Value |  |  |
Private equity funds | 4,000,000 | 6,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 0 | 0 |
UNITED STATES | Short Term And Other Investments [Member] |  |  |
Fair Value |  |  |
Private equity funds | 1,000,000 | 2,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 0 | 0 |
International [Member] | Common And Preferred Stock [Member] |  |  |
Fair Value |  |  |
Private equity funds | 126,000,000 | 191,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 89,000,000 | 125,000,000 |
International [Member] | Private Equity And Hedge Funds [Member] |  |  |
Fair Value |  |  |
Private equity funds | 61,000,000 | 59,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 34,000,000 | 35,000,000 |
International [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 1,000,000 | 28,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 0 | 21,000,000 |
International [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 62,000,000 | 59,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 0 | 0 |
International [Member] | Buy-in Annuity [Member] |  |  |
Fair Value |  |  |
Private equity funds | 11,000,000 | 12,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 0 | 0 |
International [Member] | Short Term And Other Investments [Member] |  |  |
Fair Value |  |  |
Private equity funds | 2,000,000 | 1,000,000 |
Defined Benefit Plan, Net Asset Value of Plan Assets | 0 | 0 |
Fair Value, Inputs, Level 1 |  |  |
Fair Value |  |  |
Private equity funds | 184,000,000 | 289,000,000 |
Fair Value, Inputs, Level 1 | UNITED STATES | Common And Preferred Stock [Member] |  |  |
Fair Value |  |  |
Private equity funds | 81,000,000 | 144,000,000 |
Fair Value, Inputs, Level 1 | UNITED STATES | Private Equity And Hedge Funds [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 1 | UNITED STATES | Corporate Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 34,000,000 | 31,000,000 |
Fair Value, Inputs, Level 1 | UNITED STATES | US Treasury and Government [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 15,000,000 |
Fair Value, Inputs, Level 1 | UNITED STATES | Common Collective Trust Fund [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 1 | UNITED STATES | Short Term And Other Investments [Member] |  |  |
Fair Value |  |  |
Private equity funds | 1,000,000 | 2,000,000 |
Fair Value, Inputs, Level 1 | International [Member] | Common And Preferred Stock [Member] |  |  |
Fair Value |  |  |
Private equity funds | 37,000,000 | 66,000,000 |
Fair Value, Inputs, Level 1 | International [Member] | Private Equity And Hedge Funds [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 1 | International [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 1 | International [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 29,000,000 | 31,000,000 |
Fair Value, Inputs, Level 1 | International [Member] | Buy-in Annuity [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 1 | International [Member] | Short Term And Other Investments [Member] |  |  |
Fair Value |  |  |
Private equity funds | 2,000,000 | 0 |
Fair Value, Inputs, Level 2 |  |  |
Fair Value |  |  |
Private equity funds | 51,000,000 | 87,000,000 |
Fair Value, Inputs, Level 2 | UNITED STATES | Common And Preferred Stock [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 2 | UNITED STATES | Private Equity And Hedge Funds [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 2 | UNITED STATES | Corporate Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 26,000,000 |
Fair Value, Inputs, Level 2 | UNITED STATES | US Treasury and Government [Member] |  |  |
Fair Value |  |  |
Private equity funds | 2,000,000 | 7,000,000 |
Fair Value, Inputs, Level 2 | UNITED STATES | Common Collective Trust Fund [Member] |  |  |
Fair Value |  |  |
Private equity funds | 4,000,000 | 6,000,000 |
Fair Value, Inputs, Level 2 | UNITED STATES | Short Term And Other Investments [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 2 | International [Member] | Common And Preferred Stock [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 2 | International [Member] | Private Equity And Hedge Funds [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 2 | International [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 1,000,000 | 7,000,000 |
Fair Value, Inputs, Level 2 | International [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 33,000,000 | 28,000,000 |
Fair Value, Inputs, Level 2 | International [Member] | Buy-in Annuity [Member] |  |  |
Fair Value |  |  |
Private equity funds | 11,000,000 | 12,000,000 |
Fair Value, Inputs, Level 2 | International [Member] | Short Term And Other Investments [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 1,000,000 |
Fair Value, Inputs, Level 3 |  |  |
Fair Value |  |  |
Private equity funds | 59,000,000 | 60,000,000 |
Fair Value, Inputs, Level 3 | UNITED STATES | Common And Preferred Stock [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 3 | UNITED STATES | Private Equity And Hedge Funds [Member] |  |  |
Fair Value |  |  |
Private equity funds | 32,000,000 | 36,000,000 |
Fair Value, Inputs, Level 3 | UNITED STATES | Corporate Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 3 | UNITED STATES | US Treasury and Government [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 3 | UNITED STATES | Common Collective Trust Fund [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 3 | UNITED STATES | Short Term And Other Investments [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 3 | International [Member] | Common And Preferred Stock [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 3 | International [Member] | Private Equity And Hedge Funds [Member] |  |  |
Fair Value |  |  |
Private equity funds | 27,000,000 | 24,000,000 |
Fair Value, Inputs, Level 3 | International [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 3 | International [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 3 | International [Member] | Buy-in Annuity [Member] |  |  |
Fair Value |  |  |
Private equity funds | 0 | 0 |
Fair Value, Inputs, Level 3 | International [Member] | Short Term And Other Investments [Member] |  |  |
Fair Value |  |  |
Private equity funds | $ 0 | $ 0 |

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- Definition Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees. + 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 (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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