Acquisitions and Dispositions (Schedule of Acquisitions of Solar Projects) (Details) $ in Millions		1 Months Ended
		Jul. 31, 2015 USD ($) Project MW	Jun. 30, 2015 USD ($) Project MW		Apr. 30, 2015 USD ($) Project MW		Dec. 31, 2014 USD ($) Project MW		Nov. 30, 2014 USD ($) Project MW	Mar. 31, 2014 USD ($) Project MW
Business Acquisition [Line Items]
Project Cost (millions)			$ 66
Recurrent Energy Development Holdings, LLC
Business Acquisition [Line Items]
Number of Projects | Project										6
Initial Acquisition Cost (millions)	[1]									$ 50
Project Cost (millions)	[2]									$ 446
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 (millions)	[2]								$ 80
MW Capacity | MW									20
EDF Renewable Development, Inc.
Business Acquisition [Line Items]
Number of Projects | Project			1		3		1
Initial Acquisition Cost (millions)			$ 68	[3]	$ 106	[1],[4]	$ 71	[1]
Project Cost (millions)	[2]		$ 68		$ 108		$ 71
MW Capacity | MW			18		24		20
EC&R NA Solar PV, LLC
Business Acquisition [Line Items]
Number of Projects | Project					1
Initial Acquisition Cost (millions)	[1]				$ 66
Project Cost (millions)	[2]				$ 66
MW Capacity | MW					20
Subsequent Event | SunPeak Solar, LLC
Business Acquisition [Line Items]
Number of Projects | Project		1
Initial Acquisition Cost (millions)	[3]	$ 42
Project Cost (millions)	[2]	$ 70
MW Capacity | MW		20

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

[2] Includes acquisition cost.

[3] The allocation of the purchase price to individual assets is under evaluation by management and has not been finalized.

[4] Marin Carport is expected to begin commercial operations in late 2015 or early 2016.