Revenue (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Threshold percentage of total revenue			2.00%
Revenue recognized that was included in the contract liability balance at the beginning of the period	$ 218	$ 174	$ 511	$ 454
Performance obligation satisfied in previous period	27	$ 37	44	$ 61
Mercer
Disaggregation of Revenue [Line Items]
Revenue, remaining performance obligation	$ 240		$ 240