Business Acquisitions and Dispositions Business Acquisitions and Dispositions - Transfer of Assets (Details) $ in Millions	Dec. 31, 2016 USD ($)	Sep. 01, 2016 USD ($)	Dec. 31, 2015 USD ($)	Nov. 02, 2015 USD ($) facility MW	Jan. 02, 2015 USD ($)	Jun. 30, 2014 USD ($)
Business Acquisition [Line Items]
Long-term Debt	$ 19,406.0		$ 19,620.0
CVSR [Member]
Business Acquisition [Line Items]
Percentage of Ownership Sold of Subsidiary		51.05%
Consideration Paid for Sale of Assets Under Common Control		$ 78.5
ROFO Assets [Member]
Business Acquisition [Line Items]
Percentage of Ownership Sold of Subsidiary				75.00%
Consideration Paid for Sale of Assets Under Common Control				$ 209.0	$ 489.0	$ 357.0
Long-term Debt				$ 193.0	737.0	612.0
Number of Facilities | facility				12
Power Generation Capacity, Megawatts | MW				814
Consideration Paid for Sale of Assets Under Common Control, net of Working Capital Adjustments				$ 207.0
NRG Yield, Inc. [Member] | CVSR [Member]
Business Acquisition [Line Items]
Long-term Debt		$ 496.0
Financial Institutions [Member] | ROFO Assets [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value				159.0
Working Capital Adjustment [Member] | ROFO Assets [Member]
Business Acquisition [Line Items]
Consideration Paid for Sale of Assets Under Common Control				$ 2.0	$ 9.0	8.0
Base Purchase Price [Member] | ROFO Assets [Member]
Business Acquisition [Line Items]
Consideration Paid for Sale of Assets Under Common Control						$ 349.0