Summary of Significant Accounting Policies (Tables) |
12 Months Ended | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Dec. 31, 2016 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Accounting Policies [Abstract] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Summary of Impacts of Revisions to the Risk-Free Discount Rate Applied to Environmental Remediation Liabilities and Recovery Assets | The following table summarizes the impacts of revisions in the risk-free discount rate applied to our environmental remediation liabilities and recovery assets during the reported periods (in millions) and the risk-free discount rate applied as of each reporting date:
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Schedule of Estimated Useful Lives for Significant Property and Equipment Categories | The estimated useful lives for significant property and equipment categories are as follows (in years):
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Summary of Equity and Cost Method Investments | The following table summarizes our equity and cost method investments as of December 31 (in millions):
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Schedule of Supplemental Cash Flow Information | Supplemental Cash Flow Information
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