Financing Minimum Principle Payments (Details) - USD ($) |
Dec. 31, 2017 |
Dec. 31, 2016 |
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|---|---|---|---|---|---|
| Debt Instrument [Line Items] | |||||
| Principle due prior to 2019 | $ 0 | ||||
| Principle due in 2019 | 800,000,000 | ||||
| Principle due in 2020 | 0 | ||||
| Principle due in 2021 | 750,000,000 | ||||
| Principle due thereafter | 1,572,400,000 | ||||
| Long-term debt | [1] | 3,122,400,000 | |||
| Debt discounts, premiums and issuance costs | 18,200,000 | $ 20,100,000 | |||
| Long-term Debt | 4,056,200,000 | 3,358,000,000 | |||
| Commercial Paper [Member] | |||||
| Debt Instrument [Line Items] | |||||
| Long-term Debt | 948,600,000 | ||||
| Term Loan [Member] | |||||
| Debt Instrument [Line Items] | |||||
| Principle due in 2019 | 500,000,000 | ||||
| Principle due in 2020 | 0 | ||||
| Principle due in 2021 | 0 | ||||
| Principle due thereafter | 122,400,000 | ||||
| Long-term debt | [1] | 622,400,000 | |||
| Senior Notes [Member] | |||||
| Debt Instrument [Line Items] | |||||
| Principle due in 2019 | 300,000,000 | ||||
| Principle due in 2020 | 0 | ||||
| Principle due in 2021 | 750,000,000 | ||||
| Principle due thereafter | 1,450,000,000 | ||||
| Long-term debt | [1] | 2,500,000,000 | |||
| Other Debt [Member] | |||||
| Debt Instrument [Line Items] | |||||
| Long-term Debt | $ 3,400,000 | $ 3,300,000 | |||
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