Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Income Tax Information
Tax benefit related to reduction in company's unrecognized tax benefits		$ 57
Pre-tax benefit on associated accrued interest reversals		50
Continuing Operations [Member]
Income Tax Information
Tax benefit related to reduction in company's unrecognized tax benefits		53
Pre-tax benefit on associated accrued interest reversals		47
Discontinued Operations [Member]
Income Tax Information
Tax benefit related to reduction in company's unrecognized tax benefits		4
Pre-tax benefit on associated accrued interest reversals		$ 3
2016 RTA [Member]
Income Tax Information
Other Tax Expense (Benefit)	$ 29