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Fair Value Measurements (Narrative) (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Assets transferred between Level 1 and Level 2 | $ 0 |
Adjustments to acquisition related contingent consideration liability | 3,000,000 |
Increase in fair value of contingent consideration due to 5% increase in projections | 18,000,000 |
Decrease in fair value of contingent consideration due to 5% decrease in projections | 19,000,000 |
Equity method investments | $ 405,000,000 | $ 389,000,000
Minimum |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Revenue target period (in years) | 2 years |
Maximum |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Revenue target period (in years) | 4 years |
Private Equity Funds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity method investments | $ 76,000,000 | $ 79,000,000
Money Market Funds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Share price (Rand) | $ 1.00 |

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- Definition This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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