Income Taxes (Narrative) (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Income Tax Disclosure [Abstract]
Income tax rate	26.60%		24.90%
Decrease in income tax percentage	0.050		0.073
Tax benefits from settlement of IRS audit		$ 110		$ 152
Tax expense from partial reversal of tax basis benefit associated with deemed repatriation tax	$ 41		$ 82
Tax expense from valuation allowance on foreign tax credit carryforwards no longer realizable	34
Tax Reform Act, net tax benefits	13		2
Unrecognized tax benefits	68		68		$ 66
Unrecognized tax benefits that would impact the effective tax rate	43		43		43
Unrecognized tax benefits that would impact deferred taxes	25		25		$ 23
Possible decrease in unrecognized tax benefits	$ 39		$ 39