Principles of Consolidation And Other Matters (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Operating funds related to regulatory requirements or as collateral under captive insurance arrangements	$ 272,000,000		$ 270,000,000
Equity method investments lag period	3 months
Gain (loss) on investment income, net	$ 11,000,000	$ (2,000,000)
Effective tax rate (as a percent)	24.50%	23.80%
Excess tax benefit related to share-based payments, percent	1.10%	2.60%
Unrecognized tax benefits	$ 96,000,000		$ 98,000,000
Minimum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Reasonably possible decrease in unrecognized tax benefits	0
Maximum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Reasonably possible decrease in unrecognized tax benefits	$ 35,000,000