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Investment in Unconsolidated Entities, Narrative (Details) - USD ($) $ in Millions | Mar. 31, 2018 | Jan. 01, 2018
--- | --- | ---
Equity Securities without Readily Determinable Fair Value [Line Items] |  |
Measurement alternative, impairment | $ 0 |
Measurement alternative, observable price change | 0 |
Schedule of Equity Method Investments [Line Items] |  |
Cumulative effect of accounting changes | 195 |
Retained earnings |  |
Schedule of Equity Method Investments [Line Items] |  |
Cumulative effect of accounting changes | $ 165 |
Financial instruments | Retained earnings |  |
Schedule of Equity Method Investments [Line Items] |  |
Cumulative effect of accounting changes |  | $ 1

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