Income Taxes - Possible Changes and Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reasonably possible change in unrecognized tax benefits
Unused foreign tax credits expiring in 2020 through 2027	$ 124	$ 413
Unused research tax credits expiring from 2019 to 2036	16
Operating and capital loss carryforwards with indefinite life	160
Operating and capital loss carryforwards expiring between 2018 and 2037	182
Reconciliation of the Company's total gross unrecognized tax benefits
Balance at beginning of the period	74	74	$ 77
Additions and reductions for tax positions of prior years	1		1
Additions based on tax positions related to the current year	17	15	10
Reduction due to lapse of the applicable statute of limitations	(7)	(3)	(5)
Reductions due to settlements	(9)	(12)	(1)
Foreign currency translation	3
Foreign currency translation			(8)
Balance at ending of the period	79	74	74
Unrecognized tax benefits, which if recognized, would impact the Company's effective income tax rate	72	66	67
Accrued interest and penalties	8	23	25
Interest and penalties included in tax expense	$ (14)	$ (2)	$ (1)
Period during which unrecognized tax benefits are reasonably possible of being settled as a result of audit settlements or statute expirations	12 months
Maximum
Reconciliation of the Company's total gross unrecognized tax benefits
Reasonably possible decrease in unrecognized tax benefits related to audit settlements or statute expirations	$ 7