| **Fair Value Measurements - Table 1 (Details) (Restricted Marketable Securities [Member], USD $)In Millions, unless otherwise specified** | 12 Months Ended |
|-------------------------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| Prepaid Expenses and Other Current Assets [Member]                                                                                        |            |   |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                                             |            |   |
| Available-for-sale Securities, Fair Value                                                                                                 | $ 4.7           | $ 16.4 |
| Fair Value, Valuation Techniques                                                                                                          | M               | M |
| Prepaid Expenses and Other Current Assets [Member] | Fair Value, Inputs, Level 1 [Member]                                                 |            |   |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                                             |            |   |
| Available-for-sale Securities, Fair Value                                                                                                 | 0               | 0 |
| Prepaid Expenses and Other Current Assets [Member] | Fair Value, Inputs, Level 2 [Member]                                                 |            |   |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                                             |            |   |
| Available-for-sale Securities, Fair Value                                                                                                 | 4.7             | 16.4 |
| Prepaid Expenses and Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member]                                                 |            |   |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                                             |            |   |
| Available-for-sale Securities, Fair Value                                                                                                 | 0               | 0 |
| Other Long-Term Assets [Member]                                                                                                           |            |   |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                                             |            |   |
| Available-for-sale Securities, Fair Value                                                                                                 | 42.9            | 39.4 |
| Fair Value, Valuation Techniques                                                                                                          | M               | M |
| Other Long-Term Assets [Member] | Fair Value, Inputs, Level 1 [Member]                                                                    |            |   |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                                             |            |   |
| Available-for-sale Securities, Fair Value                                                                                                 | 0               | 0 |
| Other Long-Term Assets [Member] | Fair Value, Inputs, Level 2 [Member]                                                                    |            |   |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                                             |            |   |
| Available-for-sale Securities, Fair Value                                                                                                 | 42.9            | 39.4 |
| Other Long-Term Assets [Member] | Fair Value, Inputs, Level 3 [Member]                                                                    |            |   |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                                             |            |   |
| Available-for-sale Securities, Fair Value                                                                                                 | $ 0             | $ 0 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.
+ References
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| X                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Description of the inputs and valuation technique(s) used to measure fair value.
+ References
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