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Commitments and Contingencies - Narrative (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Feb. 22, 2019
Operating Leases, Rent Expense |  |  |  |
Rent expense | $ 173,000,000 | $ 166,000,000 | $ 161,000,000 |
Loss Contingency, Estimate [Abstract] |  |  |  |
Accrual for legal proceedings and unasserted claims | $ 0 | $ 1,000,000 |  |
Percent of bid credit in each auction | 25.00% |  |  |
Subsequent Event |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
Commitment to purchase assets |  |  |  | $ 129,000,000

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- Definition Amount of loss contingency liability. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 + Details
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- Definition Minimum amount of purchase arrangement maturing in the next fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments. + References No definition available. + Details
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