Fair Value Measurements (Financial Assets And (Liabilities) Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions | Mar. 31, 2020 | Dec. 31, 2019 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investment security | $ 27 | $ 26 |
Restricted investments | | 414 |
Short-term Investments [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Restricted investments | | 414 |
Long-term investments [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Restricted investments | 393 | |
Recurring [Member] | Short-term Investments [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Time deposits | 48 | 466 |
Equity investment security | 27 | 26 |
Recurring [Member] | Other Current Assets [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative financial instruments, assets | 13 | 35 |
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 | (11) | (8) |
Derivative financial instruments, liabilities | (42) | (8) |
Recurring [Member] | Other Noncurrent Assets [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative financial instruments, assets | | 8 |
Recurring [Member] | Other Noncurrent Liabilities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Contingent consideration liabilities | (9) | (30) |
Derivative financial instruments, liabilities | (36) | (2) |
Recurring [Member] | Long-term investments [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Restricted investments | 393 | |
Recurring [Member] | Money Market Funds [Member] | Cash Equivalents [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Money market funds | 1,562 | 1,646 |
Recurring [Member] | Commercial Paper [Member] | Cash Equivalents [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Money market funds | 1,498 | |
Recurring [Member] | Level 1 [Member] | Short-term Investments [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Time deposits | 0 | 0 |
Equity investment security | 27 | 26 |
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 | 0 |
Derivative financial instruments, liabilities | 0 | 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 |
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 | 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 | 1,562 | 1,646 |
Recurring [Member] | Level 2 [Member] | Short-term Investments [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Time deposits | 48 | 466 |
Equity investment security | 0 | 0 |
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 | 13 | 35 |
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 | 0 |
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 | | 8 |
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 | (36) | (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 | 393 | |
Recurring [Member] | Level 2 [Member] | Other Current Liabilities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative financial instruments, liabilities | (42) | (8) |
Recurring [Member] | Level 2 [Member] | Money Market Funds [Member] | Cash Equivalents [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Money market funds | | 0 |
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 | 1,498 | |
Recurring [Member] | Level 3 [Member] | Short-term Investments [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Time deposits | 0 | 0 |
Equity investment security | 0 | 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] | | |
Derivative financial instruments, liabilities | 0 | 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 |
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 | (9) | (30) |
Derivative financial instruments, liabilities | 0 | 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) | (8) |
Recurring [Member] | Level 3 [Member] | Money Market Funds [Member] | Cash Equivalents [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Money market funds | | $ 0 |