Acquisitions and Dispositions (Schedule of Acquisitions of Solar Projects) (Details) $ in Millions		1 Months Ended														3 Months Ended	12 Months Ended
		Oct. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Nov. 30, 2015 USD ($) project MW	Aug. 31, 2015 USD ($)	Jul. 31, 2015 USD ($) project MW	Jun. 30, 2015 USD ($) project MW	May 31, 2015 USD ($)		Apr. 30, 2015 USD ($) project MW		Jan. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) project MW	Nov. 30, 2014 USD ($) project MW	Mar. 31, 2014 USD ($) project MW	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($) project	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Business Acquisition [Line Items]
Project Cost																	$ 40	$ 418	$ 206
Recurrent Energy Development Holdings, LLC
Business Acquisition [Line Items]
Number of Projects | project															6
Initial Acquisition Cost (millions)	[1]														$ 50
Project Cost	[2]															$ 428
MW Capacity | MW															139
CSI Project Holdco, LLC
Business Acquisition [Line Items]
Number of Projects | project														1
Initial Acquisition Cost (millions)	[1]													$ 79
Project Cost	[2]													$ 79
MW Capacity | MW														20
EDF Renewable Development, Inc.
Business Acquisition [Line Items]
Number of Projects | project							1			3	[3]		1
Initial Acquisition Cost (millions)	[1]						$ 68			$ 106	[3]		$ 71
Project Cost	[2]					$ 68		$ 106	[3]			$ 71
MW Capacity | MW							18			24	[3]		20
Number of projects that commenced operations | project	[3]																1
EC&R NA Solar PV, LLC
Business Acquisition [Line Items]
Number of Projects | project				1						1
Initial Acquisition Cost (millions)	[1]			$ 65						$ 66
Project Cost	[2]		$ 65					$ 66
MW Capacity | MW				20						20
SunPeak Solar, LLC
Business Acquisition [Line Items]
Number of Projects | project						1
Initial Acquisition Cost (millions)	[1]					$ 42
Project Cost	[2]				$ 71
MW Capacity | MW						20
Community Energy, Inc.
Business Acquisition [Line Items]
Number of Projects | project				1
Initial Acquisition Cost (millions)	[1]			$ 34
Project Cost	[2]	$ 212
MW Capacity | MW				80

[1] The purchase price was primarily allocated to Property, Plant and Equipment.

[2] Includes acquisition cost.

[3] One of the projects, Marin Carport, began commercial operations in 2016.