Variable Interest Entities (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($) MW
Sempra Solar Holdings, LLC
Variable Interest Entity [Line Items]
Ownership percentage	50.00%
Variable Interest Entity, Not Primary Beneficiary | Copper Mountain Solar 3 (d) | Nevada
Variable Interest Entity [Line Items]
Generating Capacity (MW AC) | MW	128
Power Purchase Agreement Term (in Years)	20 years
Maximum Exposure to Loss	$ 169
Variable Interest Entity, Not Primary Beneficiary | Mesquite Solar 1 (d) | Arizona
Variable Interest Entity [Line Items]
Generating Capacity (MW AC) | MW	83
Power Purchase Agreement Term (in Years)	20 years
Maximum Exposure to Loss	$ 101
Variable Interest Entity, Not Primary Beneficiary | Copper Mountain Solar 2 (d) | Nevada
Variable Interest Entity [Line Items]
Generating Capacity (MW AC) | MW	75
Power Purchase Agreement Term (in Years)	25 years
Maximum Exposure to Loss	$ 80
Variable Interest Entity, Not Primary Beneficiary | California Solar (d) | California
Variable Interest Entity [Line Items]
Generating Capacity (MW AC) | MW	55
Power Purchase Agreement Term (in Years)	25 years
Maximum Exposure to Loss	$ 59
Variable Interest Entity, Not Primary Beneficiary | Broken Bow II (d) | Nebraska
Variable Interest Entity [Line Items]
Generating Capacity (MW AC) | MW	38
Power Purchase Agreement Term (in Years)	25 years
Maximum Exposure to Loss	$ 42
Variable Interest Entity, Primary Beneficiary | Texas Solar 4
Variable Interest Entity [Line Items]
Percentage of variable interests	80.00%
Maximum exposure for consolidated investments	$ 7
Variable Interest Entity, Primary Beneficiary | Texas Solar 4 | Texas
Variable Interest Entity [Line Items]
Generating Capacity (MW AC) | MW	32
Power Purchase Agreement Term (in Years)	25 years
Maximum Exposure to Loss	$ 19
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure
Variable Interest Entity [Line Items]
Percentage of variable interests	50.00%