Debt - Other Debt Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended			3 Months Ended				12 Months Ended
	Dec. 31, 2018	Feb. 28, 2017	Feb. 29, 2016	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Weighted average interest rate of short term debt borrowings	0.60%			0.60%				0.60%	2.10%
Long-term Debt, Fiscal Year Maturity [Abstract]
2019	$ 1,523			$ 1,523				$ 1,523
2020	1,642			1,642				1,642
2021	1,864			1,864				1,864
2022	2,336			2,336				2,336
2023	1,788			1,788				1,788
Thereafter	4,658			4,658				4,658
Carrying value of long-term debt including current portion	13,811			13,811				13,811	$ 8,762
Pledge assets as collateral	74			74				74
Secured long term debt	81			$ 81				81
Repayments of long-term debt								3,124	583	$ 770
Interest charge								$ 26	$ 0	$ 16
Extinguishment of debt, gain (loss), net of tax	$ 20	$ 10
Diluted earnings per share from continuing operations (in dollars per share)	$ 0.06	$ 0.04		$ 6.22	$ 1.58	$ 1.65	$ 1.59	$ 12.79	$ 4.32	$ 5.21
US Long-term 5.20% Notes due 2017
Long-term Debt, Fiscal Year Maturity [Abstract]
Repayments of long-term debt		$ 325	$ 325
Interest rate		5.20%	5.20%
Interest charge			$ 16
Extinguishment of debt, gain (loss), net of tax			$ 10
Diluted earnings per share from continuing operations (in dollars per share)			$ 0.04