Fair Value Measurements and Fair Value of Financial Instruments Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - Contingent Consideration [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 37	$ 35
Acquisitions (including assumed balances)	24	11
Payments	(3)	(8)
Change in fair value included in earnings	(3)	(1)
Ending Balance	$ 55	$ 37
Fair Value, Recurring Basis, Unobservable Input Reconciliation, Asset (Liability), Gain (Loss), Statement of Income [Extensible List]	us-gaap:SellingGeneralAndAdministrativeExpense