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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]	12 Months Ended
	Dec. 31, 2017
Minimum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Weighted average cost of capital ("WACC")	11.50%
Maximum [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Weighted average cost of capital ("WACC")	14.50%
Weighted Average [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Revenue multiple	0.9
Weighted Average [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Weighted average cost of capital ("WACC")	12.60%

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Market valuation of entity divided by revenue, used as an input to measure fair value.

+ 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

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