Accumulated Other Comprehensive Income (AOCI) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance of Accumulated Other Comprehensive Income (Loss) at Beginning of Period	$ (1,637)
Other comprehensive income (loss) before reclassifications	186
Amounts reclassified from AOCI	0
Other comprehensive income (loss), tax, portion attributable to parent	0
Other Comprehensive Income (Loss), Net of Tax	186
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(1,451)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance of Accumulated Other Comprehensive Income (Loss) at Beginning of Period	(1,353)
Other comprehensive income (loss) before reclassifications	211
Amounts reclassified from AOCI	0
Other comprehensive income (loss), tax, portion attributable to parent	(3)
Other Comprehensive Income (Loss), Net of Tax	208
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(1,145)
Deferred Gain (Loss) On Hedging Activities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance of Accumulated Other Comprehensive Income (Loss) at Beginning of Period	17
Other comprehensive income (loss) before reclassifications	(17)
Amounts reclassified from AOCI	(8)
Other comprehensive income (loss), tax, portion attributable to parent	6
Other Comprehensive Income (Loss), Net of Tax	(19)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(2)
Pension Liability Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance of Accumulated Other Comprehensive Income (Loss) at Beginning of Period	(321)
Other comprehensive income (loss) before reclassifications	(6)
Amounts reclassified from AOCI	8
Other comprehensive income (loss), tax, portion attributable to parent	(3)
Other Comprehensive Income (Loss), Net of Tax	(1)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(322)
Unrealized Gain (Loss) On Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance of Accumulated Other Comprehensive Income (Loss) at Beginning of Period	20
Other comprehensive income (loss) before reclassifications	(2)
Amounts reclassified from AOCI	0
Other comprehensive income (loss), tax, portion attributable to parent	0
Other Comprehensive Income (Loss), Net of Tax	(2)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	$ 18