Receivables (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Total receivables	$ 1,406	$ 1,330
Government receivables
Financing Receivable, Past Due [Line Items]
Total receivables	1,056	872
Pharmacy rebate receivables
Financing Receivable, Past Due [Line Items]
Total receivables	150	146
Health insurer fee reimbursement receivables
Financing Receivable, Past Due [Line Items]
Total receivables	5	141
Other
Financing Receivable, Past Due [Line Items]
Total receivables	$ 195	$ 171