Shareholders' Equity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	$ (1,637)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(2,106)	$ (1,637)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(580)	690
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	(1,353)	(2,102)
Net realized gains (losses)	(1)	0
Other Comprehensive Income (Loss), Tax	(28)	59
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(609)	749
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(1,962)	(1,353)
Deferred Gain (Loss) On Hedging Activities [Member]
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(19)	(35)
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	17	6
Net realized gains (losses)	76	47
Other Comprehensive Income (Loss), Tax	(13)	(1)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	44	11
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	61	17
Pension Liability Adjustment [Member]
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	124	243
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	(321)	(521)
Net realized gains (losses)	32	55
Other Comprehensive Income (Loss), Tax	(55)	(98)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	101	200
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(220)	(321)
Unrealized Gain (Loss) On Investments [Member]
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(2)	0
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	20	19
Net realized gains (losses)	(2)	(1)
Other Comprehensive Income (Loss), Tax	(1)	2
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(5)	1
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	15	20
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(477)	898
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	(1,637)	(2,598)
Net realized gains (losses)	105	101
Other Comprehensive Income (Loss), Tax	(97)	(38)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(469)	961
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	$ (2,106)	$ (1,637)