Acquisitions (Details) - Distributed energy [Domain] - USD ($) $ in Millions		12 Months Ended
	Feb. 18, 2015	Dec. 31, 2015	Sep. 16, 2016
Business Acquisition [Line Items]
Goodwill, Acquired During Period		$ 16
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Business Combination, Consideration Transferred, Other	$ 5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		$ 4
Business Combination, Consideration Transferred	25
Payments to Acquire Businesses, Gross	$ 20
Business Acquisition, Transaction Costs			$ 43