Fair Value Measurements (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | |
Jun. 30, 2015 | Jun. 30, 2015 | Dec. 31, 2014 |
Available-for-sale securities: | | | |
Available-for-sale securities | $ 1,952.1 | $ 1,952.1 | $ 2,070.8 |
Trading securities: | | | |
Trading securities | 17.9 | 17.9 | 16.3 |
Fair Value Measurements (Textuals) | | | |
Restricted investments | 41.2 | 41.2 | 41.3 |
Asset-backed Securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 331.1 | 331.1 | 269 |
Certificates of deposit [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 4.7 | 4.7 | 10.6 |
Commercial paper [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 12.5 | 12.5 | 20.3 |
Corporate debt securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 917.5 | 917.5 | 738 |
Foreign government debt securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 26 | 26 | 24.6 |
Government-sponsored enterprise obligations [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 172.7 | 172.7 | 162.1 |
Money market funds [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 207.5 | 207.5 | 594.2 |
Mutual funds [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 4 | 4 | 4 |
Publicly-traded equity securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 8 | 8 | 2 |
US government securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 268.1 | 268.1 | 246 |
Privately-held debt and redeemable preferred stock securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 1,732.6 | 1,732.6 | 1,470.6 |
Fair Value, Measurements, Recurring [Member] | | | |
Derivative assets: | | | |
Total assets measured at fair value | 2,021.6 | 2,021.6 | 2,134.7 |
Liabilities measured at fair value: | | | |
Other accrued liabilities | (1.7) | (1.7) | (3.9) |
Total liabilities measured at fair value | (1.7) | (1.7) | (3.9) |
Cash equivalents | 178.8 | 178.8 | 576.6 |
Restricted investments | 45.2 | 45.2 | 45.2 |
Short-term investments | 517.7 | 517.7 | 332.2 |
Long-term investments | 1,228.3 | 1,228.3 | 1,133.1 |
Prepaid expenses and other current assets | 1.3 | 1.3 | 0.1 |
Other long-term assets | 50.3 | 50.3 | 47.5 |
Fair Value, Measurements, Recurring [Member] | Foreign exchange contract [Member] | | | |
Derivative assets: | | | |
Foreign exchange contracts | 1.3 | 1.3 | 0.1 |
Liabilities measured at fair value: | | | |
Derivative liabilities | (1.7) | (1.7) | (3.9) |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Derivative assets: | | | |
Total assets measured at fair value | 505.5 | 505.5 | 862.5 |
Liabilities measured at fair value: | | | |
Other accrued liabilities | 0 | 0 | 0 |
Total liabilities measured at fair value | 0 | 0 | 0 |
Cash equivalents | 166.4 | 166.4 | 552.9 |
Restricted investments | 45.2 | 45.2 | 45.2 |
Short-term investments | 176.6 | 176.6 | 87 |
Long-term investments | 117.3 | 117.3 | 177.4 |
Prepaid expenses and other current assets | 0 | 0 | 0 |
Other long-term assets | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign exchange contract [Member] | | | |
Derivative assets: | | | |
Foreign exchange contracts | 0 | 0 | 0 |
Liabilities measured at fair value: | | | |
Derivative liabilities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Derivative assets: | | | |
Total assets measured at fair value | 1,465.8 | 1,465.8 | 1,224.7 |
Liabilities measured at fair value: | | | |
Other accrued liabilities | (1.7) | (1.7) | (3.9) |
Total liabilities measured at fair value | (1.7) | (1.7) | (3.9) |
Cash equivalents | 12.4 | 12.4 | 23.7 |
Restricted investments | 0 | 0 | 0 |
Short-term investments | 341.1 | 341.1 | 245.2 |
Long-term investments | 1,111 | 1,111 | 955.7 |
Prepaid expenses and other current assets | 1.3 | 1.3 | 0.1 |
Other long-term assets | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign exchange contract [Member] | | | |
Derivative assets: | | | |
Foreign exchange contracts | 1.3 | 1.3 | 0.1 |
Liabilities measured at fair value: | | | |
Derivative liabilities | (1.7) | (1.7) | (3.9) |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Derivative assets: | | | |
Total assets measured at fair value | 50.3 | 50.3 | 47.5 |
Liabilities measured at fair value: | | | |
Other accrued liabilities | 0 | 0 | 0 |
Total liabilities measured at fair value | 0 | 0 | 0 |
Cash equivalents | 0 | 0 | 0 |
Restricted investments | 0 | 0 | 0 |
Short-term investments | 0 | 0 | 0 |
Long-term investments | 0 | 0 | 0 |
Prepaid expenses and other current assets | 0 | 0 | 0 |
Other long-term assets | 50.3 | 50.3 | 47.5 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign exchange contract [Member] | | | |
Derivative assets: | | | |
Foreign exchange contracts | 0 | 0 | 0 |
Liabilities measured at fair value: | | | |
Derivative liabilities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 331.1 | 331.1 | 269 |
Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 331.1 | 331.1 | 269 |
Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Certificates of deposit [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 4.7 | 4.7 | 10.6 |
Fair Value, Measurements, Recurring [Member] | Certificates of deposit [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Certificates of deposit [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 4.7 | 4.7 | 10.6 |
Fair Value, Measurements, Recurring [Member] | Certificates of deposit [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 12.5 | 12.5 | 20.3 |
Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 12.5 | 12.5 | 20.3 |
Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 917.5 | 917.5 | 738 |
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 917.5 | 917.5 | 738 |
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Foreign government debt securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 26 | 26 | 24.6 |
Fair Value, Measurements, Recurring [Member] | Foreign government debt securities [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Foreign government debt securities [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 26 | 26 | 24.6 |
Fair Value, Measurements, Recurring [Member] | Foreign government debt securities [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Government-sponsored enterprise obligations [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 172.7 | 172.7 | 162.1 |
Fair Value, Measurements, Recurring [Member] | Government-sponsored enterprise obligations [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Government-sponsored enterprise obligations [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 172.7 | 172.7 | 162.1 |
Fair Value, Measurements, Recurring [Member] | Government-sponsored enterprise obligations [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Money market funds [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 207.5 | 207.5 | 594.2 |
Fair Value, Measurements, Recurring [Member] | Money market funds [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 207.5 | 207.5 | 594.2 |
Fair Value, Measurements, Recurring [Member] | Money market funds [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Money market funds [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 4 | 4 | 4 |
Trading securities: | | | |
Trading securities | 17.9 | 17.9 | 16.3 |
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 4 | 4 | 4 |
Trading securities: | | | |
Trading securities | 17.9 | 17.9 | 16.3 |
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Trading securities: | | | |
Trading securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Trading securities: | | | |
Trading securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Publicly-traded equity securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 8 | 8 | 2 |
Fair Value, Measurements, Recurring [Member] | Publicly-traded equity securities [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 8 | 8 | 2 |
Fair Value, Measurements, Recurring [Member] | Publicly-traded equity securities [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Publicly-traded equity securities [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | US government securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 268.1 | 268.1 | 246 |
Fair Value, Measurements, Recurring [Member] | US government securities [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 268.1 | 268.1 | 246 |
Fair Value, Measurements, Recurring [Member] | US government securities [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | US government securities [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Available-for-sale securities [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 1,952.1 | 1,952.1 | 2,070.8 |
Fair Value, Measurements, Recurring [Member] | Available-for-sale securities [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 487.6 | 487.6 | 846.2 |
Fair Value, Measurements, Recurring [Member] | Available-for-sale securities [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 1,464.5 | 1,464.5 | 1,224.6 |
Fair Value, Measurements, Recurring [Member] | Available-for-sale securities [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Available-for-sale securities: | | | |
Available-for-sale securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Privately-held debt and redeemable preferred stock securities [Member] | | | |
Trading securities: | | | |
Privately-held debt and redeemable preferred stock securities | 50.3 | 50.3 | 47.5 |
Fair Value, Measurements, Recurring [Member] | Privately-held debt and redeemable preferred stock securities [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Trading securities: | | | |
Privately-held debt and redeemable preferred stock securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Privately-held debt and redeemable preferred stock securities [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Trading securities: | | | |
Privately-held debt and redeemable preferred stock securities | 0 | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Privately-held debt and redeemable preferred stock securities [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Trading securities: | | | |
Privately-held debt and redeemable preferred stock securities | 50.3 | 50.3 | $ 47.5 |
Fair Value Measurements (Textuals) | | | |
Purchases of privately-held investments | $ 0 | $ 2.8 | |