Provision for Income Taxes (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Tax benefit related to reduction in company's unrecognized tax benefits	$ (57)
Pre-tax benefit on associated accrued interest reversals	50
Continuing Operations [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Tax benefit related to reduction in company's unrecognized tax benefits	(53)
Pre-tax benefit on associated accrued interest reversals	47
Discontinued Operations [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Tax benefit related to reduction in company's unrecognized tax benefits	(4)
Pre-tax benefit on associated accrued interest reversals	$ 3