Fair Value Measurements (Financial Assets And (Liabilities) Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, current	$ 2,097.6	$ 2,014.8
U.S. Treasury And Agency Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, current	598.9	527.1
Corporate And Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, current	394.0	360.5
Certificates of Deposit and Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, current	719.1	754.0
Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, current	241.9	229.6
Municipal Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, current	121.1	121.3
Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, current	22.6	22.3
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	717.9	495.9
Time deposits	830.3	809.5
Available-for-sale investment securities	2,075.0	1,992.5
Investments	2,905.3	2,802.0
Total	3,630.5	3,282.7
Recurring [Member] | Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	16.7	7.6
Recurring [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	(8.0)	(10.9)
Recurring [Member] | Other Noncurrent Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	5.9	1.6
Recurring [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities	(7.3)	(13.5)
Recurring [Member] | U.S. Treasury And Agency Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	598.9	527.1
Recurring [Member] | Corporate And Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	394.0	360.5
Recurring [Member] | Certificates of Deposit and Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	719.1	754.0
Recurring [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	241.9	229.6
Recurring [Member] | Municipal Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	121.1	121.3
Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	260.9	495.9
Recurring [Member] | Bank Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	323.0
Recurring [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	134.0
Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	260.9	495.9
Time deposits	0.0	0.0
Available-for-sale investment securities	540.2	463.7
Investments	540.2	463.7
Total	801.1	959.6
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	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]
Derivative financial instruments, liabilities	0.0	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	0.0	0.0
Recurring [Member] | Level 1 [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities	0.0	0.0
Recurring [Member] | Level 1 [Member] | U.S. Treasury And Agency Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	540.2	463.7
Recurring [Member] | Level 1 [Member] | Corporate And Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	0.0	0.0
Recurring [Member] | Level 1 [Member] | Certificates of Deposit and Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	0.0	0.0
Recurring [Member] | Level 1 [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	0.0	0.0
Recurring [Member] | Level 1 [Member] | Municipal Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	0.0	0.0
Recurring [Member] | Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	260.9	495.9
Recurring [Member] | Level 1 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0
Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	457.0	0.0
Time deposits	830.3	809.5
Available-for-sale investment securities	1,534.8	1,528.8
Investments	2,365.1	2,338.3
Total	2,829.4	2,323.1
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	16.7	7.6
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]
Derivative financial instruments, liabilities	(8.0)	(10.9)
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	5.9	1.6
Recurring [Member] | Level 2 [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities	(7.3)	(13.5)
Recurring [Member] | Level 2 [Member] | U.S. Treasury And Agency Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	58.7	63.4
Recurring [Member] | Level 2 [Member] | Corporate And Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	394.0	360.5
Recurring [Member] | Level 2 [Member] | Certificates of Deposit and Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	719.1	754.0
Recurring [Member] | Level 2 [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	241.9	229.6
Recurring [Member] | Level 2 [Member] | Municipal Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	121.1	121.3
Recurring [Member] | Level 2 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0
Recurring [Member] | Level 2 [Member] | Bank Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	323.0
Recurring [Member] | Level 2 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	134.0
Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0
Time deposits	0.0	0.0
Available-for-sale investment securities	0.0	0.0
Investments	0.0	0.0
Total	0.0	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	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	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	0.0	0.0
Recurring [Member] | Level 3 [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities	0.0	0.0
Recurring [Member] | Level 3 [Member] | U.S. Treasury And Agency Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	0.0	0.0
Recurring [Member] | Level 3 [Member] | Corporate And Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	0.0
Recurring [Member] | Level 3 [Member] | Certificates of Deposit and Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	0.0	0.0
Recurring [Member] | Level 3 [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	0.0	0.0
Recurring [Member] | Level 3 [Member] | Municipal Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities	0.0	0.0
Recurring [Member] | Level 3 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		$ 0.0
Recurring [Member] | Level 3 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 0.0