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Fair Value Measurements - Quantitative Information used in Valuing Level 3 Liabilities (Details) - Discounted Cash Flow - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2018 | Dec. 31, 2017
Contingent Payment Arrangements |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |
Fair value liabilities | $ 4.2 | $ 9.4
Growth rate (as a percent) | 7.00% |
Discount rate (as a percent) | 15.00% |
Contingent Payment Arrangements | Minimum |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |
Growth rate (as a percent) |  | 7.00%
Discount rate (as a percent) |  | 15.00%
Contingent Payment Arrangements | Maximum |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |
Growth rate (as a percent) |  | 8.00%
Discount rate (as a percent) |  | 16.00%
Affiliate Equity Obligations |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |
Fair value liabilities | $ 36.9 | $ 49.2
Affiliate Equity Obligations | Minimum |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |
Growth rate (as a percent) | 0.00% | 0.00%
Discount rate (as a percent) | 12.00% | 12.00%
Affiliate Equity Obligations | Maximum |  |
Quantitative information for Level 3 Fair Value Measurements Liabilities |  |
Growth rate (as a percent) | 11.00% | 11.00%
Discount rate (as a percent) | 16.00% | 16.00%

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- Definition Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- 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. + Details
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- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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