Fair Value Measurements - Narrative (Details) - USD ($)
$ in Millions |
|
1 Months Ended |
3 Months Ended |
9 Months Ended |
|
|
Apr. 21, 2017 |
May 31, 2019 |
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
Dec. 31, 2018 |
Mar. 07, 2018 |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
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| Development expenses |
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|
$ 7
|
$ (3)
|
|
|
| Tsugaru Holdings |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Additional earn-out payment possible |
|
|
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$ 118
|
| Contingent consideration |
|
|
|
|
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|
106
|
| Tsugaru Holdings | Term Conversion Of Tsugaru Construction Loan |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Increase in additional earn-out payment |
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|
$ 10
|
|
10
|
|
|
10
|
| Decrease in additional earn-out payment |
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|
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|
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|
10
|
| Contingent consideration |
|
|
1
|
|
1
|
|
|
$ 103
|
| Development expenses |
|
|
9
|
|
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|
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| Broadview Project |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Contingent consideration |
$ 21
|
|
|
|
|
|
|
|
| Development expenses |
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|
4
|
|
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|
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|
| Transmission wheeling revenue, period |
25 years
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| Energy derivative |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Asset, change in unrealized gain (loss) |
|
|
0
|
$ 0
|
(7)
|
(15)
|
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|
| Pattern Energy Group LP | Broadview Project |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
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| Contingent consideration paid |
|
$ 25
|
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| Recurring Measurement Basis |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
|
|
|
|
|
| Contingent consideration |
|
|
122
|
|
122
|
|
$ 130
|
|
| Recurring Measurement Basis | Contingent Consideration | Other Income (Expense), Net |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
|
|
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| Liability, change in unrealized gain (loss) |
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|
$ (2)
|
$ (2)
|
$ (6)
|
$ (7)
|
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