Contingencies (Federal Government's Lawsuit) (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2024	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2022	Dec. 31, 2021
Loss Contingencies [Line Items]
Loss contingency accrual, provision					$ 90
Federal Government's Lawsuit
Loss Contingencies [Line Items]
Loss Contingency, Corrective Statements In Newspapers, Period			4 months
Loss Contingency, Corrective Statements On Television, Period			1 year
Loss Contingency, Corrective Statements, Onserts Total Period		2 years
Implementation of Corrective Communications [Member]
Loss Contingencies [Line Items]
Loss Contingency, Corrective Statements, Onserts Period		14 days
Loss Contingency, Corrective Statements, Onserts Consecutive Total Period		3 months
Implementation of Corrective Communications [Member] | Federal Government's Lawsuit
Loss Contingencies [Line Items]
Loss contingency accrual, provision	$ 15			$ 28