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Pension and Other Postemployment Benefits (Details 4) - Pension - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015
Reconciliation of changes in the fair value of pension investments |  |
Beginning balance | $ 5,345 |
Actual return on plan assets: |  |
Ending balance | 6,198 | $ 5,345
Private Equity Funds |  |
Reconciliation of changes in the fair value of pension investments |  |
Beginning balance | 24 |
Actual return on plan assets: |  |
Ending balance | 33 | 24
Real Estate Funds |  |
Reconciliation of changes in the fair value of pension investments |  |
Beginning balance | 587 |
Actual return on plan assets: |  |
Ending balance | 615 | 587
Level 3 |  |
Reconciliation of changes in the fair value of pension investments |  |
Beginning balance | 611 |
Actual return on plan assets: |  |
Ending balance | 648 | 611
Level 3 | Private Equity Funds |  |
Reconciliation of changes in the fair value of pension investments |  |
Beginning balance | 24 | 25
Actual return on plan assets: |  |
Unrealized gains | 1 | 0
Realized gains (losses) | 1 | (1)
Transfers in (out) | 7 | 0
Ending balance | 33 | 24
Level 3 | Real Estate Funds |  |
Reconciliation of changes in the fair value of pension investments |  |
Beginning balance | 587 | 421
Actual return on plan assets: |  |
Unrealized gains | 29 | 42
Realized gains (losses) | 14 | 16
Transfers in (out) | (15) | 108
Ending balance | $ 615 | $ 587

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