Shareholders' Equity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	$ (2,146)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(2,598)	$ (2,146)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(391)	(984)
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	(1,626)	(654)
Net realized gains (losses)	(75)	23
Other Comprehensive Income (Loss), Tax	(10)	(11)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(476)	(972)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(2,102)	(1,626)
Deferred Gain (Loss) On Hedging Activities [Member]
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(104)	(53)
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	(15)	47
Net realized gains (losses)	137	(46)
Other Comprehensive Income (Loss), Tax	(12)	37
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	21	(62)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	6	(15)
Pension Liability Adjustment [Member]
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(28)	87
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	(523)	(630)
Net realized gains (losses)	27	67
Other Comprehensive Income (Loss), Tax	3	(47)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	2	107
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	(521)	(523)
Unrealized Gain (Loss) On Investments [Member]
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(3)	20
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	18	(4)
Net realized gains (losses)	6	0
Other Comprehensive Income (Loss), Tax	(2)	2
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1	22
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	19	18
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(526)	(930)
Accumulated other comprehensive income (loss)
Balance of Accumulated Other Comprehensive Income (Loss) at beginning of period	(2,146)	(1,241)
Net realized gains (losses)	95	44
Other Comprehensive Income (Loss), Tax	(21)	(19)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(452)	(905)
Balance of Accumulated Other Comprehensive Income (Loss) at End of period	$ (2,598)	$ (2,146)