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Investment in Unconsolidated Entities, Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2018 | Jan. 01, 2018
Equity Securities without Readily Determinable Fair Value [Line Items] |  |  |
Measurement alternative, impairment | $ 0 | $ 0 |
Measurement alternative, observable price change | 0 | 0 |
Schedule of Equity Method Investments [Line Items] |  |  |
Cumulative effect of accounting changes | 193 | 193 |
Retained earnings |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Cumulative effect of accounting changes | $ 163 | $ 163 |
ASU 2016-01 | Retained earnings |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Cumulative effect of accounting changes |  |  | $ 1

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