Leases - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating leases	$ 783
Operating lease assets		$ 802	$ 829
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]		us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Operating lease, weighted-average remaining lease term		8 years	8 years
Operating lease, weighted-average discount rate		3.70%	4.10%