Fair Value of Financial Instruments Quantitative Information About Significant Unobservable Inputs (Footnote Information) (Detail)	12 Months Ended
Dec. 31, 2017
Equity Warrant Asset, Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Weighted average contractual remaining term	5 years 9 months 85 days
Estimated remaining life	2 years 7 months 30 days
Lower Limit
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Marketability discount	10.00%
Duration of the sale restrictions	3 months
Upper Limit
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Marketability discount	20.00%
Duration of the sale restrictions	6 months

Fair Value Inputs, Sales Restrictions, Period

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- Definition

Financial Instruments Fair Value Assumptions Contractual Weighted Average Remaining Life

+ References

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- Definition

Financial Instruments Fair Value Assumptions Estimated Weighted Average Remaining Life

+ References

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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.

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- Definition

Adjustment to the discount rate used to measure fair value for lack of ability to convert business interests into cash quickly.

+ 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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