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, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 35	$ 6
Acquisitions	11	17
Payments	(8)	(3)
Change in fair value included in earnings	(1)	15
Ending Balance	$ 37	$ 35