Non-Wholly Owned Entities and Contingently Redeemable Noncontrolling Interest - Income from Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Triton [Member]
Schedule of Equity Method Investments [Line Items]
Income from equity method investment	$ 1	$ 1	$ 1	$ 1
Horizon Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Income from equity method investment	$ 0	$ 0	$ 1	$ 1