Income Taxes - Reconciliation of the beginning and ending amount of unrecognized tax benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of the Company's beginning and ending amount of unrecognized tax benefits
Balance at the beginning of the period	$ 299	$ 279
Additions based on tax positions related to the current year	25	23
Additions for tax positions of prior years	7	12
Reductions for tax positions of prior years	(3)	(5)
Settlements	0	(5)
Business combinations	0	0
Lapse of statute of limitations	(7)	(5)
Foreign currency translation, increase	0	0
Balance at the end of the period	$ 321	$ 299