Income Taxes Income Taxes - Deferred Tax Assets and Liabilities Table (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Deferred Tax Liabilities, Deferred Expense, Other Capitalized Costs	$ (223)	$ (802)
Deferred Tax Liabilities, Derivatives	0	(300)
Deferred Tax Liabilities, Other	(62)	(71)
Deferred Tax Liabilities, Gross	285	1,173
Deferred Tax Assets, Property, Plant and Equipment	593	1,144
Deferred Tax Assets, Operating Loss Carryforwards	2,587	1,556
Deferred Tax Assets, Carrying Value of Debt	539	532
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Asset Retirement Obligations	98	174
Deferred Tax Assets, Investments	275	260
Deferred Tax Assets, Derivative Instruments	161	0
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities	319	333
Deferred Tax Assets, Other	118	123
Deferred Tax Assets, Gross	4,690	4,122
Deferred Tax Assets, Valuation Allowance	(4,389)	(2,949)
Deferred Tax Assets, Net of Valuation Allowance	301	1,173
Deferred Tax Assets, Net	$ 16	$ 0