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Employee Benefit Plans - Defined Benefit Plan, Information about Plan Assets (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Significant Unobservable Inputs (Level 3) |  |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Settlements | $ 0 | $ 0
Corporate | Significant Unobservable Inputs (Level 3) |  |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Settlements | 0 | 0
Residential mortgage-backed securities ("RMBS") | Significant Unobservable Inputs (Level 3) |  |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Settlements | 0 | 0
Foreign government/government agencies | Significant Unobservable Inputs (Level 3) |  |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Settlements | 0 | 0
Mortgage loans | Significant Unobservable Inputs (Level 3) |  |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Settlements | 0 | 0
Other investments | Significant Unobservable Inputs (Level 3) |  |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Settlements | 0 | 0
Pension Benefits |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 3,914 | 3,344
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 3,914 | 3,344
Fair value of plan assets — end of year | 4,363 | 3,914
Defined Benefit Plan, Fair Value of Plan Assets, Excluded Investment Payables | 20 | 40
Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 724 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 724 |
Fair value of plan assets — end of year | 859 | 724
Pension Benefits | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 2,420 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 2,420 |
Fair value of plan assets — end of year | 2,599 | 2,420
Pension Benefits | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 160 | 151
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 160 | 151
Realized gains (losses), net | (1) | 3
Changes in unrealized gains, net | 6 | 6
Purchases | 56 | 7
Sales | (9) | (11)
Transfers into Level 3 | 0 | 4
Transfers out of Level 3 | 2 | 0
Fair value of plan assets — end of year | 210 | 160
Pension Benefits | Fair Value, Inputs, Level 1, 2 and 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 3,874 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 3,874 |
Fair value of plan assets — end of year | $ 4,343 | 3,874
Pension Benefits | Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 40.00% |
Pension Benefits | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 60.00% |
Pension Benefits | Short-term Investments [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | $ 88 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 88 |
Fair value of plan assets — end of year | 100 | 88
Pension Benefits | Short-term Investments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 34 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 34 |
Fair value of plan assets — end of year | 75 | 34
Pension Benefits | Short-term Investments [Member] | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 54 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 54 |
Fair value of plan assets — end of year | 25 | 54
Pension Benefits | Short-term Investments [Member] | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | Corporate |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 2,085 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 2,085 |
Fair value of plan assets — end of year | 2,342 | 2,085
Pension Benefits | Corporate | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | Corporate | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 2,058 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 2,058 |
Fair value of plan assets — end of year | 2,303 | 2,058
Pension Benefits | Corporate | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 27 | 14
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 27 | 14
Realized gains (losses), net | 0 | 3
Changes in unrealized gains, net | 1 | 2
Purchases | 14 | 7
Sales | (3) | (3)
Transfers into Level 3 | 0 | 4
Transfers out of Level 3 |  | 0
Fair value of plan assets — end of year | 39 | 27
Pension Benefits | Residential mortgage-backed securities ("RMBS") |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 61 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 61 |
Fair value of plan assets — end of year | 42 | 61
Pension Benefits | Residential mortgage-backed securities ("RMBS") | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | Residential mortgage-backed securities ("RMBS") | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 61 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 61 |
Fair value of plan assets — end of year | 41 | 61
Pension Benefits | Residential mortgage-backed securities ("RMBS") | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 | 1
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 | 1
Realized gains (losses), net | 0 | 0
Changes in unrealized gains, net | 0 | 0
Purchases | 1 | 0
Sales | 0 | (1)
Transfers into Level 3 | 0 | 0
Transfers out of Level 3 | 0 | 0
Fair value of plan assets — end of year | 1 | 0
Pension Benefits | U.S. Treasuries |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 101 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 101 |
Fair value of plan assets — end of year | 47 | 101
Pension Benefits | U.S. Treasuries | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | U.S. Treasuries | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 101 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 101 |
Fair value of plan assets — end of year | 47 | 101
Pension Benefits | U.S. Treasuries | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | Foreign government/government agencies |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 18 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 18 |
Fair value of plan assets — end of year | 25 | 18
Pension Benefits | Foreign government/government agencies | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | Foreign government/government agencies | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 17 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 17 |
Fair value of plan assets — end of year | 16 | 17
Pension Benefits | Foreign government/government agencies | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 1 | 2
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 1 | 2
Realized gains (losses), net | 0 | 0
Changes in unrealized gains, net | 0 | 0
Purchases | 9 | 0
Sales | 0 | (1)
Transfers into Level 3 | 0 | 0
Transfers out of Level 3 | 1 | 0
Fair value of plan assets — end of year | 9 | 1
Pension Benefits | CMBS |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 32 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 32 |
Fair value of plan assets — end of year | 30 | 32
Pension Benefits | CMBS | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | CMBS | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 32 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 32 |
Fair value of plan assets — end of year | 30 | 32
Pension Benefits | CMBS | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | Other Fixed Income [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 97 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 97 |
Fair value of plan assets — end of year | 137 | 97
Pension Benefits | Other Fixed Income [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | Other Fixed Income [Member] | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 96 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 96 |
Fair value of plan assets — end of year | 137 | 96
Pension Benefits | Other Fixed Income [Member] | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 1 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 1 |
Fair value of plan assets — end of year | 0 | 1
Pension Benefits | Mortgage loans |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 131 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 131 |
Fair value of plan assets — end of year | 161 | 131
Pension Benefits | Mortgage loans | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | Mortgage loans | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | Mortgage loans | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 131 | 133
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 131 | 133
Realized gains (losses), net | 0 | 0
Changes in unrealized gains, net | 4 | 4
Purchases | 32 | 0
Sales | (6) | (6)
Transfers into Level 3 | 0 | 0
Transfers out of Level 3 | 0 | 0
Fair value of plan assets — end of year | 161 | 131
Pension Benefits | Domestic |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 430 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 430 |
Fair value of plan assets — end of year | 513 | 430
Pension Benefits | Domestic | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 429 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 429 |
Fair value of plan assets — end of year | 513 | 429
Pension Benefits | Domestic | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 1 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 1 |
Fair value of plan assets — end of year | 0 | 1
Pension Benefits | Domestic | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | International |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 261 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 261 |
Fair value of plan assets — end of year | 271 | 261
Pension Benefits | International | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 261 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 261 |
Fair value of plan assets — end of year | 271 | 261
Pension Benefits | International | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | International | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Pension Benefits | Total pension plan assets at fair value, in the fair value hierarchy |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 3,304 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 3,304 |
Fair value of plan assets — end of year | 3,668 | 3,304
Pension Benefits | Total pension plan assets at fair value, in the fair value hierarchy | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 724 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 724 |
Fair value of plan assets — end of year | 859 | 724
Pension Benefits | Total pension plan assets at fair value, in the fair value hierarchy | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 2,420 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 2,420 |
Fair value of plan assets — end of year | 2,599 | 2,420
Pension Benefits | Total pension plan assets at fair value, in the fair value hierarchy | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 160 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 160 |
Fair value of plan assets — end of year | 210 | 160
Pension Benefits | Private Market Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 358 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 358 |
Fair value of plan assets — end of year | 451 | 358
Pension Benefits | Hedge funds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 212 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 212 |
Fair value of plan assets — end of year | 224 | 212
Pension Benefits | Other investments | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 1 | 1
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 1 | 1
Realized gains (losses), net | (1) | 0
Changes in unrealized gains, net | 1 | 0
Purchases | 0 | 0
Sales | 0 | 0
Transfers into Level 3 | 0 | 0
Transfers out of Level 3 | 1 | 0
Fair value of plan assets — end of year | 0 | 1
Pension Benefits | Defined Benefit Plan, Equity Securities, Common Stock [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 1 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 1 |
Fair value of plan assets — end of year | 1 | 1
Other Postretirement Benefits |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 75 | 85
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 75 | 85
Fair value of plan assets — end of year | 63 | 75
Other Postretirement Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 22 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 22 |
Fair value of plan assets — end of year | 19 | 22
Other Postretirement Benefits | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 53 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 53 |
Fair value of plan assets — end of year | 44 | 53
Other Postretirement Benefits | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | $ 0 | 0
Other Postretirement Benefits | Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 30.00% |
Other Postretirement Benefits | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 70.00% |
Other Postretirement Benefits | Short-term Investments [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | $ 3 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 3 |
Fair value of plan assets — end of year | 2 | 3
Other Postretirement Benefits | Short-term Investments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 3 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 3 |
Fair value of plan assets — end of year | 2 | 3
Other Postretirement Benefits | Short-term Investments [Member] | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | Short-term Investments [Member] | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | Corporate |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 18 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 18 |
Fair value of plan assets — end of year | 16 | 18
Other Postretirement Benefits | Corporate | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | Corporate | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 18 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 18 |
Fair value of plan assets — end of year | 16 | 18
Other Postretirement Benefits | Corporate | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | Residential mortgage-backed securities ("RMBS") |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 12 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 12 |
Fair value of plan assets — end of year | 9 | 12
Other Postretirement Benefits | Residential mortgage-backed securities ("RMBS") | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | Residential mortgage-backed securities ("RMBS") | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 12 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 12 |
Fair value of plan assets — end of year | 9 | 12
Other Postretirement Benefits | Residential mortgage-backed securities ("RMBS") | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | U.S. Treasuries |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 20 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 20 |
Fair value of plan assets — end of year | 16 | 20
Other Postretirement Benefits | U.S. Treasuries | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | U.S. Treasuries | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 20 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 20 |
Fair value of plan assets — end of year | 16 | 20
Other Postretirement Benefits | U.S. Treasuries | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | CMBS |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 1 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 1 |
Fair value of plan assets — end of year | 1 | 1
Other Postretirement Benefits | CMBS | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | CMBS | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 1 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 1 |
Fair value of plan assets — end of year | 1 | 1
Other Postretirement Benefits | CMBS | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | Other Fixed Income [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 2 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 2 |
Fair value of plan assets — end of year | 2 | 2
Other Postretirement Benefits | Other Fixed Income [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | Other Fixed Income [Member] | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 2 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 2 |
Fair value of plan assets — end of year | 2 | 2
Other Postretirement Benefits | Other Fixed Income [Member] | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | Large-cap |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 19 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 19 |
Fair value of plan assets — end of year | 17 | 19
Other Postretirement Benefits | Large-cap | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 19 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 19 |
Fair value of plan assets — end of year | 17 | 19
Other Postretirement Benefits | Large-cap | Significant Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | Large-cap | Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | 0 | 0
Other Postretirement Benefits | Defined Benefit Plan, Equity Securities, Common Stock [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets — beginning of year | 0 |
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |  |
Fair value of plan assets — beginning of year | 0 |
Fair value of plan assets — end of year | $ 0 | $ 0
Minimum | Pension Benefits | Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 5.00% |
Minimum | Pension Benefits | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 50.00% |
Minimum | Pension Benefits | Alternative assets |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 0.00% |
Minimum | Other Postretirement Benefits | Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 15.00% |
Minimum | Other Postretirement Benefits | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 55.00% |
Minimum | Other Postretirement Benefits | Alternative assets |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 0.00% |
Maximum | Pension Benefits | Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 35.00% |
Maximum | Pension Benefits | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 70.00% |
Maximum | Pension Benefits | Alternative assets |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 45.00% |
Maximum | Other Postretirement Benefits | Equity Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 45.00% |
Maximum | Other Postretirement Benefits | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 85.00% |
Maximum | Other Postretirement Benefits | Alternative assets |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 0.00% |

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