Basis of Presentation and Significant Accounting Policies Basis of Presentation and Significant Accounting Policies Fair Value Revisions Table (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term Debt, Fair Value	$ 9,483	$ 9,325
Fair Value, Inputs, Level 1 [Member] | Reported Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Short-term Debt, Fair Value	503	381
Long-term Debt, Fair Value	3,271	6,720
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Short-term Debt, Fair Value	511	366
Long-term Debt, Fair Value	3,216	2,546
Fair Value, Inputs, Level 1 [Member] | Scenario, Previously Reported [Member] | Reported Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Short-term Debt, Fair Value		381
Long-term Debt, Fair Value		10,347
Fair Value, Inputs, Level 1 [Member] | Scenario, Previously Reported [Member] | Estimate of Fair Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Short-term Debt, Fair Value		366
Long-term Debt, Fair Value		3,735
Fair Value, Inputs, Level 1 [Member] | Restatement Adjustment [Member] | Reported Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Short-term Debt, Fair Value		0
Long-term Debt, Fair Value		(3,627)
Fair Value, Inputs, Level 1 [Member] | Restatement Adjustment [Member] | Estimate of Fair Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Short-term Debt, Fair Value		0
Long-term Debt, Fair Value		(1,189)
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term Debt, Fair Value	6,664	3,584
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term Debt, Fair Value	$ 6,654	1,189
Fair Value, Inputs, Level 2 [Member] | Scenario, Previously Reported [Member] | Reported Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term Debt, Fair Value		0
Fair Value, Inputs, Level 2 [Member] | Scenario, Previously Reported [Member] | Estimate of Fair Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term Debt, Fair Value		0
Fair Value, Inputs, Level 2 [Member] | Restatement Adjustment [Member] | Reported Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term Debt, Fair Value		3,584
Fair Value, Inputs, Level 2 [Member] | Restatement Adjustment [Member] | Estimate of Fair Value Measurement [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term Debt, Fair Value		$ 1,189