Acquisitions of Ownership Interests in Partner Companies and Funds (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired	$ 3,250	$ 15,101
Equity method investments	64,489	108,089
Prognos [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired		1,000
Equity method investments			$ 11,600
CloudMine [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		4,500
Equity method investments		10,000	5,500
Hoopla Software, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan		300
Equity method investments			4,800
Zipnosis [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired	1,500
Equity method investments		7,000
WebLinc [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	1,000	2,000
Equity method investments		14,000	12,000
Cask Data [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	400	2,000
Equity method investments		13,000	11,000
InfoBionic [Member]
Schedule of Equity Method Investments [Line Items]
Financing receivable, gross	700
Convertible bridge loan	1,600	5,300
Equity method investments		19,700	14,500
Sonobi [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	2,200	3,800
Equity method investments		9,200	5,400
meQuilibrium [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired	1,000	2,500
Equity method investments		10,500	8,000
Spongecell [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	500	600
Equity method investments		18,600	18,000
Aventura [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan		300
Equity method investments		0	6,200
BrickWork [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	700
Equity method investments		4,200
QuanticMind, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	1,400
Acquisitions of ownership interests in companies and funds, net of cash acquired		1,800
Equity method investments		11,500	9,700
Aktana, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired	500	1,500
Equity method investments		9,700	8,200
Moxe Health [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	1,000
Equity method investments		4,500
Full Measure [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired		3,100
Equity method investments			8,600
Trice [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired		2,100
Equity method investments			8,000
Propeller [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired	300
Equity method investments		14,000
Syapse, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired		2,300
Equity method investments			13,300
Lumesis, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan		200
Equity method investments			6,200
NovaSom, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	$ 2,200	2,000
Equity method investments		24,100	22,100
Good Start Genetics Inc [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan		$ 1,800
Equity method investments			$ 17,200