Basis of Presentation Out of period adjustment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Income Tax Expense (Benefit)	$ (7)	$ (24)	$ (19)	$ (55)
Reduction to costs and expenses	$ (1,507)	(1,647)	(3,082)	$ (3,386)
Previously report
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Income Tax Expense (Benefit)		(25)
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Income Tax Expense (Benefit)		$ (6)
Compensation-related Accrual Adjustment | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Reduction to costs and expenses			$ 4