Acquisitions of Ownership Interests in Partner Companies and Funds (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired		$ 11,640	$ 3,250
Equity method investments		34,542	64,489
Syapse, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired	$ 5,000
Equity method investments			15,600
Moxe Health [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan		300	1,000
Acquisitions of ownership interests in companies and funds, net of cash acquired		2,000
Equity method investments			5,500
Aktana, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired	1,500		500
Equity method investments			10,200
meQuilibrium [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired	1,500		1,000
Equity method investments			11,500
CloudMine [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan			1,000
Equity method investments				$ 10,000
Zipnosis [Member]
Schedule of Equity Method Investments [Line Items]
Acquisitions of ownership interests in companies and funds, net of cash acquired	1,500		1,500
Equity method investments			8,500
InfoBionic [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan			1,600
Acquisitions of ownership interests in companies and funds, net of cash acquired	400
Equity method investments			16,300	19,700
InfoBionic [Member] | Term Notes [Member]
Schedule of Equity Method Investments [Line Items]
Increase in notes receivable			700
BrickWork [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan			700
Equity method investments				4,200
Sonobi [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	2,000		2,200
Equity method investments			11,400
WebLinc [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan		1,100	1,000
Equity method investments			15,000
Nova Som Inc [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	$ 1,000		2,200
Equity method investments			26,400
QuanticMind, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan		$ 600	1,400
Equity method investments			12,900
Spongecell [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan			500
Equity method investments				18,600
Cask Data [Member]
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan			400
Equity method investments				13,000
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