Financing Minimum Principle Payments (Detail) - USD ($) |
Mar. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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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 | 1,450,000,000 | |||||
| Long-term debt | [1] | 3,000,000,000 | ||||
| Debt discounts, premiums and issuance costs | $ 19,300,000 | 20,100,000 | ||||
| Long-term Debt | 3,262,700,000 | 3,358,000,000 | $ 0 | |||
| Commercial Paper [Member] | ||||||
| Debt Instrument [Line Items] | ||||||
| Long-term Debt | 374,800,000 | |||||
| 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 | 0 | |||||
| Long-term debt | [1] | 500,000,000 | ||||
| Notes Payable to Banks [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 | $ 3,200,000 | $ 3,300,000 | ||||
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