Fair Value Measurements (Financial Assets And (Liabilities) Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity	$ 27		$ 27
Available-for-sale securities, current	105
Long-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted investments	397		405
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	40	$ 54	54	$ 38
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issuances	8	42
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	(19)	(23)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	(3)	$ (3)
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity			27
Recurring [Member] | Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity	27
Available-for-sale securities, current	105
Recurring [Member] | Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	36		46
Recurring [Member] | Accrued Expenses And Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities	(27)
Derivative financial instruments, liabilities	(2)
Recurring [Member] | Other Noncurrent Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	9		26
Recurring [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities	(13)		(43)
Derivative financial instruments, liabilities	(2)
Recurring [Member] | Long-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted investments	397		405
Recurring [Member] | Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities			(11)
Derivative financial instruments, liabilities			(1)
Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	260		209
Recurring [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	285		200
Recurring [Member] | Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	4		203
Recurring [Member] | Level 1 [Member] | Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity	27		27
Available-for-sale securities, current	0
Recurring [Member] | Level 1 [Member] | Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	0		0
Recurring [Member] | Level 1 [Member] | Accrued Expenses And Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities	0
Derivative financial instruments, liabilities	0
Recurring [Member] | Level 1 [Member] | Other Noncurrent Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	0		0
Recurring [Member] | Level 1 [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities	0		0
Derivative financial instruments, liabilities	0
Recurring [Member] | Level 1 [Member] | Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities			0
Derivative financial instruments, liabilities			0
Recurring [Member] | Level 1 [Member] | Money Market Funds [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	260		209
Recurring [Member] | Level 2 [Member] | Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity	0		0
Available-for-sale securities, current	105
Recurring [Member] | Level 2 [Member] | Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	36		46
Recurring [Member] | Level 2 [Member] | Accrued Expenses And Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities	0
Derivative financial instruments, liabilities	(2)
Recurring [Member] | Level 2 [Member] | Other Noncurrent Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	9		26
Recurring [Member] | Level 2 [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities	0		0
Derivative financial instruments, liabilities	(2)
Recurring [Member] | Level 2 [Member] | Long-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted investments	397		405
Recurring [Member] | Level 2 [Member] | Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities			0
Derivative financial instruments, liabilities			(1)
Recurring [Member] | Level 2 [Member] | Commercial Paper [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	285		200
Recurring [Member] | Level 2 [Member] | Time Deposits | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	4		203
Recurring [Member] | Level 3 [Member] | Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity	0		0
Available-for-sale securities, current	0
Recurring [Member] | Level 3 [Member] | Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	0		0
Recurring [Member] | Level 3 [Member] | Accrued Expenses And Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities	(27)
Derivative financial instruments, liabilities	0
Recurring [Member] | Level 3 [Member] | Other Noncurrent Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	0		0
Recurring [Member] | Level 3 [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities	(13)		(43)
Derivative financial instruments, liabilities	0
Recurring [Member] | Level 3 [Member] | Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liabilities			(11)
Derivative financial instruments, liabilities			0
Time Deposits | Recurring [Member] | Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short term investments	323		3
Time Deposits | Recurring [Member] | Level 1 [Member] | Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short term investments	0		0
Time Deposits | Recurring [Member] | Level 2 [Member] | Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short term investments	323		3
Time Deposits | Recurring [Member] | Level 3 [Member] | Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short term investments	$ 0		$ 0