Accumulated Other Comprehensive Income (AOCI) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance of Accumulated Other Comprehensive Income (Loss) at Beginning of Period	$ (1,911)	$ (1,637)
Other comprehensive income (loss) before reclassifications	(179)	(489)
Amounts reclassified from AOCI	79	120
Other comprehensive income (loss), tax, portion attributable to parent	(21)	(26)
Other Comprehensive Income (Loss), Net of Tax	(121)	(395)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(2,032)	(2,032)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance of Accumulated Other Comprehensive Income (Loss) at Beginning of Period	(1,566)	(1,353)
Other comprehensive income (loss) before reclassifications	(177)	(368)
Amounts reclassified from AOCI	(1)	(1)
Other comprehensive income (loss), tax, portion attributable to parent	(1)	(23)
Other Comprehensive Income (Loss), Net of Tax	(179)	(392)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(1,745)	(1,745)
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	(51)	17
Other comprehensive income (loss) before reclassifications	5	(110)
Amounts reclassified from AOCI	72	98
Other comprehensive income (loss), tax, portion attributable to parent	(17)	4
Other Comprehensive Income (Loss), Net of Tax	60	(8)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	9	9
Pension Liability Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance of Accumulated Other Comprehensive Income (Loss) at Beginning of Period	(310)	(321)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from AOCI	8	23
Other comprehensive income (loss), tax, portion attributable to parent	(3)	(7)
Other Comprehensive Income (Loss), Net of Tax	5	16
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(305)	(305)
Unrealized Gain (Loss) On Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance of Accumulated Other Comprehensive Income (Loss) at Beginning of Period	16	20
Other comprehensive income (loss) before reclassifications	(7)	(11)
Amounts reclassified from AOCI	0	0
Other comprehensive income (loss), tax, portion attributable to parent	0	0
Other Comprehensive Income (Loss), Net of Tax	(7)	(11)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	$ 9	$ 9