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Investment - Summary of Ranges and Weighted Averages of Significant Unobservable Inputs Used to Determine Enterprise Value (Detail) - Thesys Group, Inc [Member] - Preferred Stock [Member] - Level 3 [Member] - Income Approach Valuation Technique [Member] | 12 Months Ended
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Dec. 31, 2018
Minimum [Member] |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |
Weighted average cost of capital ("WACC") | 3.80%
Maximum [Member] |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |
Weighted average cost of capital ("WACC") | 15.50%
Weighted Average [Member] |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |
Weighted average cost of capital ("WACC") | 14.10%

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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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