Ownership Interests in and Advances to Partner Companies and Funds - Summary of the carrying value of the Company's ownership interests in and advances to partner companies and private equity funds (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Investments in and Advances to Affiliates [Line Items]
Fair value	$ 0	$ 20,057,000
Equity method investments	135,989,000us-gaap_EquityMethodInvestments	110,638,000us-gaap_EquityMethodInvestments
Cost method investments	9,138,000us-gaap_CostMethodInvestments	15,898,000us-gaap_CostMethodInvestments
Advances to partner companies	9,065,000us-gaap_AdvancesToAffiliate	1,986,000us-gaap_AdvancesToAffiliate
Total	154,192,000	148,579,000
Loan participations receivable	3,855,000	8,135,000
Partner companies [Member]
Investments in and Advances to Affiliates [Line Items]
Equity method investments	134,861,000	108,872,000
Cost method investments	6,774,000	13,480,000
Private equity funds [Member]
Investments in and Advances to Affiliates [Line Items]
Equity method investments	1,128,000	1,766,000
Cost method investments	$ 2,364,000	$ 2,418,000

Ownership Interests in and Advances to Partner Companies and Funds - Summary of the carrying value of the Company's ownership interests in and advances to partner companies and private equity funds (Detail) (USD $)

Dec. 31, 2014

Dec. 31, 2013

Investments in and Advances to Affiliates [Line Items]

Fair value

$ 0us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVenturesFairValueDisclosure

$ 20,057,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVenturesFairValueDisclosure

Equity method investments

135,989,000us-gaap_EquityMethodInvestments

110,638,000us-gaap_EquityMethodInvestments

Cost method investments

9,138,000us-gaap_CostMethodInvestments

15,898,000us-gaap_CostMethodInvestments

Advances to partner companies

9,065,000us-gaap_AdvancesToAffiliate

1,986,000us-gaap_AdvancesToAffiliate

Total

154,192,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures

148,579,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures

Loan participations receivable

3,855,000us-gaap_NotesAndLoansReceivableNetNoncurrent

8,135,000us-gaap_NotesAndLoansReceivableNetNoncurrent

Partner companies [Member]

Investments in and Advances to Affiliates [Line Items]

Equity method investments

134,861,000us-gaap_EquityMethodInvestments
/ invest_InvestmentAxis
= us-gaap_OtherOwnershipInterestMember

108,872,000us-gaap_EquityMethodInvestments
/ invest_InvestmentAxis
= us-gaap_OtherOwnershipInterestMember

Cost method investments

6,774,000us-gaap_CostMethodInvestments
/ invest_InvestmentAxis
= us-gaap_OtherOwnershipInterestMember

13,480,000us-gaap_CostMethodInvestments
/ invest_InvestmentAxis
= us-gaap_OtherOwnershipInterestMember

Private equity funds [Member]

Investments in and Advances to Affiliates [Line Items]

Equity method investments

1,128,000us-gaap_EquityMethodInvestments
/ invest_InvestmentAxis
= us-gaap_PrivateEquityFundsMember

1,766,000us-gaap_EquityMethodInvestments
/ invest_InvestmentAxis
= us-gaap_PrivateEquityFundsMember

Cost method investments

$ 2,364,000us-gaap_CostMethodInvestments
/ invest_InvestmentAxis
= us-gaap_PrivateEquityFundsMember

$ 2,418,000us-gaap_CostMethodInvestments
/ invest_InvestmentAxis
= us-gaap_PrivateEquityFundsMember

- Definition

Long-Term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership. This does not include advances to clients.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.6-04.2)

-URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6812-107765

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 2

-Article 6

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Amount, after adjustment, of cost-method investment. Adjustments include, but are not limited to, dividends received in excess of earnings after date of investment that are considered a return of investment and other than temporary impairments.

+ References

Reference 1: 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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 325

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6872867&loc=d3e40691-111596

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 325

-SubTopic 20

-Section 35

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=29638308&loc=d3e40346-111594

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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

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

+ References

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- Definition

Fair value portion of investments in an entity not consolidated. Includes, but is not limited to, investments in an entity that is affiliated with the reporting entity by means of direct or indirect ownership, an entity in which the reporting entity shares control of the entity with another party or group, an entity which the company has significant influence, but does not have control and subsidiaries that are not required to be consolidated and are accounted for using the equity or cost method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19190-110258

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- Definition

An amount representing an agreement for an unconditional promise by the maker to pay the Entity (holder) a definite sum of money at a future date more than one year from the balance sheet date, net of any write-downs taken for collection uncertainty on the part of the holder. Such amount may include accrued interest receivable in accordance with the terms of the debt. The debt also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. This amount does not include amounts related to receivables held-for-sale.

+ References

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