Acquisitions - Aggregate Disclosure Related to Business Acquisitions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Cash paid, net of cash acquired	$ 13	$ 0	$ 297
Contingent acquisition consideration	13	14
Excess purchase price allocated to goodwill	$ 3,292	$ 3,280	$ 3,280