| **Fair Value Measurements - Table 2 (Details) - USD ($) $ in Millions**                                                            | Jun. 30, 2017 | Dec. 31, 2016 |
|------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| Revolving Credit Facility [Member] | Carrying Amount [Member]                                                                      |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | $ 70.0        | $ 152.0       |
| Revolving Credit Facility [Member] | Estimated Fair Value [Member]                                                                 |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | 70.0          | 152.0         |
| Letters of Credit [Member] | Carrying Amount [Member]                                                                              |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | 0.0           | 0.0           |
| Letters of Credit [Member] | Estimated Fair Value [Member]                                                                         |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | 34.1          | 33.3          |
| Term Loan Facilities [Member] | Term Loan Facilities [Member] | Carrying Amount [Member]                                           |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | 410.2         | 421.2         |
| Term Loan Facilities [Member] | Term Loan Facilities [Member] | Estimated Fair Value [Member]                                      |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | $ 411.3       | 422.5         |
| Senior Notes [Member] | 5.125% Senior Notes Due 2023 [Member]                                                                      |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Debt instrument interest rate (percent)                                                                                            | 5.125%        |          |
| Senior Notes [Member] | 5.125% Senior Notes Due 2023 [Member] | Carrying Amount [Member]                                           |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | $ 295.6       | 295.3         |
| Senior Notes [Member] | 5.125% Senior Notes Due 2023 [Member] | Estimated Fair Value [Member]                                      |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | $ 310.5       | 297.8         |
| Senior Notes [Member] | 5.75% Senior Notes Due 2024 [Member]                                                                       |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Debt instrument interest rate (percent)                                                                                            | 5.75%         |          |
| Senior Notes [Member] | 5.75% Senior Notes Due 2024 [Member] | Carrying Amount [Member]                                            |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | $ 1,193.6     | 1,193.2       |
| Senior Notes [Member] | 5.75% Senior Notes Due 2024 [Member] | Estimated Fair Value [Member]                                       |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | $ 1,231.2     | 1,216.6       |
| Senior Notes [Member] | 5.75% Senior Notes Due 2025 [Member]                                                                       |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Debt instrument interest rate (percent)                                                                                            | 5.75%         |          |
| Senior Notes [Member] | 5.75% Senior Notes Due 2025 [Member] | Carrying Amount [Member]                                            |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | $ 344.2       | 343.9         |
| Senior Notes [Member] | 5.75% Senior Notes Due 2025 [Member] | Estimated Fair Value [Member]                                       |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | $ 373.1       | 349.6         |
| Senior Subordinated Notes [Member] | 2.00% Convertible Senior Subordinated Notes due 2043 [Member]                                 |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Debt instrument interest rate (percent)                                                                                            | 2.00%         |          |
| Senior Subordinated Notes [Member] | 2.00% Convertible Senior Subordinated Notes due 2043 [Member] | Carrying Amount [Member]      |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | $ 0.0         | 275.7         |
| Senior Subordinated Notes [Member] | 2.00% Convertible Senior Subordinated Notes due 2043 [Member] | Estimated Fair Value [Member] |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | 0.0           | 382.6         |
| Other Notes Payable [Member] | Carrying Amount [Member]                                                                            |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | 74.1          | 55.8          |
| Other Notes Payable [Member] | Estimated Fair Value [Member]                                                                       |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                  |          |          |
| Carrying amounts and estimated fair values of financial instruments                                                                | $ 74.1        | $ 55.8        |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Contractual interest rate for funds borrowed, under the debt agreement.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.
+ References
No definition available.
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