Summary of Significant Accounting Policies - Business Acquisitions (Details) (Southern Power [Member], USD $) In Millions, unless otherwise specified	0 Months Ended	12 Months Ended		0 Months Ended	12 Months Ended					0 Months Ended	12 Months Ended
	Aug. 27, 2013 Adobe Solar LLC [Member]	Dec. 31, 2013 Adobe Solar LLC [Member] MW		Apr. 23, 2013 Campo Verde Solar LLC [Member]	Dec. 31, 2013 Campo Verde Solar LLC [Member] MW		Dec. 31, 2013 Spectrum Nevada Solar Llc [Member] MW		Sep. 28, 2012 Spectrum Nevada Solar Llc [Member]	Jun. 29, 2012 Apex Nevada Solar Llc [Member]	Dec. 31, 2013 Apex Nevada Solar Llc [Member] MW
Business Acquisition [Line Items]
MW Capacity		20	[1],[2]		139	[1],[3]	30	[1],[4]			20	[1]
Year of Operation		2014	[2]		2013	[3]	2013	[4]			2012
PPA Contract Period		20 years	[2]		20 years	[3]	25 years	[4]		25 years	25 years
Payments to Acquire Businesses, Gross	$ 100.0	$ 100.0	[2]	$ 136.6	$ 136.6	[3]	$ 17.6	[4]			$ 102.0
Business Acquisition Cost of Acquired Entity Purchase Consideration Cash Will Be Paid				$ 355.5					$ 104.0

[1] megawatt (MW)

[2] This acquisition is expected to occur in spring 2014, and the purchase price is expected to be $100 million.

[3] Under an engineering, procurement, and construction agreement, an additional $355.5 million was paid to a subsidiary of First Solar Inc. to complete the construction of the solar facility.

[4] Under an engineering, procurement, and construction agreement, an additional $104 million was paid to a subsidiary of Sun Edison, LLC to complete the construction of the solar facility.