Risks And Uncertainties (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) MWh segment business customer	Dec. 31, 2015 USD ($) customer	Jan. 01, 2015 USD ($)	Dec. 31, 2014 USD ($) customer	Jan. 01, 2014 USD ($)
Unusual Risk or Uncertainty [Line Items]
Number of strategic business units | segment	6
Segment Reporting, Additional Information about Entity's Reportable Segments | business	2
Cash and cash equivalents | $	$ 1,305	$ 1,257	$ 1,517	$ 1,517	$ 1,636
Percent of revenue generated outside US	74.00%
Number of customers that accounted for 10% of more of total revenue | customer	0	0		0
Percentage of total revenues from a single customer (less than)	10.00%
Alto Maipo [Member]
Unusual Risk or Uncertainty [Line Items]
Megawatts under construction | MWh	531