Accounts Receivable, Net - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Receivables [Abstract]
Allowance for receivables net current	$ 1,400	$ 1,200
Allowances for pharmaceutical manufacturers receivable	926	757
Allowances for noninsurance customer receivables	321	208
Allowances, discounts and claims adjustments issued to customers in the form of client credits	186	224
Allowance for current expected credit losses on accounts receivable	$ 60	$ 65