Acquisitions of Ownership Interests in Partner Companies and Funds (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments					$ 11,851	$ 34,841
Equity method investments	$ 114,313				114,313		$ 154,666
InfoBionic
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments							14,500
Convertible bridge loan					4,900
Cask Data
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments							11,000
Convertible bridge loan					1,600
meQuilibrium
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	2,500						8,000
Hoopla Software, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments							4,800
Convertible bridge loan	300
Novasom, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments							22,100
Convertible bridge loan					1,500
QuanticMind
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	1,800						9,700
Sonobi
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments							5,400
Convertible bridge loan		$ 3,000
WebLinc
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments							12,000
Convertible bridge loan				$ 2,000
Good Start Genetics, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments							17,200
Convertible bridge loan		1,800
Trice Medical, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments		2,100					8,000
Aktana, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments		$ 1,500					8,200
CloudMine
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments			$ 2,000				5,500
Lumesis, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments							6,200
Convertible bridge loan			200
Full Measure
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments			2,400				8,600
Aventura
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments							$ 6,200
Equity method investments	$ 0				$ 0
Convertible bridge loan			$ 300