Acquisitions of Ownership Interests in Partner Companies and Funds (Detail) - USD ($) $ in Thousands		1 Months Ended																		2 Months Ended	3 Months Ended	4 Months Ended		5 Months Ended			6 Months Ended		9 Months Ended	12 Months Ended			14 Months Ended			17 Months Ended	21 Months Ended	22 Months Ended		23 Months Ended	24 Months Ended	25 Months Ended	27 Months Ended	30 Months Ended	35 Months Ended	36 Months Ended	53 Months Ended	63 Months Ended	98 Months Ended
	Dec. 31, 2012	Dec. 31, 2015	Oct. 31, 2015	Jul. 31, 2015	Jun. 30, 2015	May. 31, 2015	Apr. 30, 2015	Mar. 31, 2015	Feb. 28, 2015	Jan. 31, 2015	Aug. 31, 2014	Jun. 30, 2014	May. 31, 2014	Mar. 31, 2014	Feb. 28, 2014	Jan. 31, 2014	Aug. 31, 2013	Jul. 31, 2013	Jun. 30, 2013	Apr. 30, 2015	Jun. 30, 2014	May. 31, 2015	Sep. 30, 2013	Jul. 31, 2015	Dec. 31, 2014	May. 31, 2014	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Apr. 30, 2014
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired																														$ 70,186	$ 59,476	$ 41,838
Proceeds from sale of business																														$ 25,058	82,822	38,974
CloudMine [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan		$ 2,000
Ownership interest under equity method, percentage									30.10%
Acquisitions of ownership interests in companies and funds, net of cash acquired									$ 2,900
Hoopla Software, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan		$ 700
Acquisitions of ownership interests in companies and funds, net of cash acquired																																														$ 3,200
Zipnosis [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage		26.30%																												26.30%
Acquisitions of ownership interests in companies and funds, net of cash acquired		$ 7,000
WebLinc [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan		$ 600
Acquisitions of ownership interests in companies and funds, net of cash acquired																									$ 6,000
Cask Data [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage			34.20%
Acquisitions of ownership interests in companies and funds, net of cash acquired			$ 11,000
Appfirst [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan																														$ 3,000
Acquisitions of ownership interests in companies and funds, net of cash acquired																																										$ 8,600
Apprenda [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired				$ 10,000																													$ 12,100
InfoBionic [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired				1,500																									$ 8,000
Quantia [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan																											$ 2,800
Acquisitions of ownership interests in companies and funds, net of cash acquired																																				$ 12,500
Proceeds from sale of business				7,800
InsideVault [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage					24.50%																						24.50%
Acquisitions of ownership interests in companies and funds, net of cash acquired					$ 7,000
Pneuron [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired						$ 3,500																																$ 5,000
Clutch [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired																						$ 4,800																	$ 7,500
Sonobi [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage						22.60%																22.60%
Acquisitions of ownership interests in companies and funds, net of cash acquired						$ 5,400
Advantedge [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan																				$ 1,000
Acquisitions of ownership interests in companies and funds, net of cash acquired																																																	$ 15,300
meQuilibrium [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage							31.50%													31.50%
Acquisitions of ownership interests in companies and funds, net of cash acquired							$ 6,500
Spongecell [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan								$ 4,000
Acquisitions of ownership interests in companies and funds, net of cash acquired																																													$ 10,000
Dabo [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan								$ 300
Payments to Acquire Other Investments																																		$ 2,000
Aventura [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage										19.90%
Acquisitions of ownership interests in companies and funds, net of cash acquired										$ 6,000
Full Measure [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage										25.40%
Acquisitions of ownership interests in companies and funds, net of cash acquired										$ 4,000
Trice [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired										$ 1,100																		$ 5,000
Propeller [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage											24.60%
Acquisitions of ownership interests in companies and funds, net of cash acquired											$ 9,000
Transactis [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage											24.80%
Acquisitions of ownership interests in companies and funds, net of cash acquired											$ 9,500
Syapse, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage												27.00%									27.00%
Acquisitions of ownership interests in companies and funds, net of cash acquired												$ 5,800
Putney, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired																					$ 5,000																						$ 10,000
Lumesis, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired																										$ 1,700														$ 3,900
NovaSom, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan													$ 1,100
Acquisitions of ownership interests in companies and funds, net of cash acquired																																												$ 20,000
MediaMath, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage													20.60%													20.60%																								22.50%
Acquisitions of ownership interests in companies and funds, net of cash acquired													$ 7,000																																		$ 18,600
Unrealized gain (loss) from change in ownership																															7,000
Sotera [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan														$ 200
Payments to Acquire Other Investments																																1,300
Cost of shares acquired from previous investor																																1,200
Proceeds from sale of business							4,200
Alverix Inc [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan																							$ 600
Acquisitions of ownership interests in companies and funds, net of cash acquired																																																$ 8,800
Proceeds from sale of business				$ 1,700												$ 15,700															15,700
DriveFactor Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired																	$ 1,100																								$ 3,500
Proceeds from sale of business							$ 9,100
Crescendo [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan																		$ 1,000
Payments to Acquire Other Investments	$ 10,000
Proceeds from sale of business															$ 38,400									$ 2,900							$ 38,400
PixelOptics, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan																																$ 5,300
Acquisitions of ownership interests in companies and funds, net of cash acquired																																					$ 31,600
Medivo, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired																			$ 5,300																$ 6,300