Acquisitions of Ownership Interests in Partner Companies and Funds (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	$ 9,500	$ 3,250
Equity method investments	35,263		$ 64,489
InfoBionic
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	400
Equity method investments			16,300
Sonobi
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	2,000
Equity method investments			11,400
Novasom, Inc.
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	1,000
Equity method investments			26,400
WebLinc
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	900
Equity method investments			15,000
Zipnosis
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	1,500
Equity method investments			8,500
Syapse, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	5,000
Equity method investments			15,600
meQuilibrium
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	1,500
Equity method investments			11,500
Aktana, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	1,500
Equity method investments			10,200
Moxe Health
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	300
Equity method investments	5,800		5,500
QuanticMind, Inc.
Schedule of Equity Method Investments [Line Items]
Convertible bridge loan	$ 400
Equity method investments			$ 12,900