Acquisitions of Ownership Interests in Partner Companies and Funds (Detail) - USD ($)	1 Months Ended					2 Months Ended	3 Months Ended	4 Months Ended		6 Months Ended	7 Months Ended	9 Months Ended		12 Months Ended	17 Months Ended	18 Months Ended	21 Months Ended	34 Months Ended	37 Months Ended	47 Months Ended		48 Months Ended	54 Months Ended	64 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Apr. 30, 2016	Mar. 31, 2016	Jan. 31, 2016	Apr. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Jul. 31, 2016	Jun. 30, 2016	Jul. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments												$ 34,841,000	$ 52,181,000
Proceeds from sales of and distributions from companies												73,854,000	$ 25,029,000
Equity method investments	$ 151,885,000							$ 151,885,000				$ 151,885,000		$ 151,840,000	$ 151,840,000	$ 151,840,000	$ 151,840,000	$ 151,840,000	$ 151,840,000	$ 151,840,000	$ 151,840,000	$ 151,840,000	$ 151,840,000	$ 151,840,000
Moxe Health
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	32.60%							32.60%				32.60%
Payments to acquire equity method investments	$ 4,500,000
Aktana, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage		23.40%								23.40%
Payments to acquire equity method investments		$ 5,500,000
InfoBionic
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments												$ 5,000,000					$ 9,500,000
AppFirst, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments																			$ 11,600,000
Proceeds from sales of and distributions from companies		$ 900,000
Equity method investments	$ 0							$ 0				$ 0
Convertible bridge loan										$ 1,200,000
Lumesis, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	44.10%							44.10%				44.10%
Payments to acquire equity method investments																				$ 5,600,000
Convertible bridge loan								$ 500,000
Novasom, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments																							$ 21,000,000
Convertible bridge loan						$ 1,000,000
Transactis
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	24.20%							24.20%				24.20%
Payments to acquire equity method investments			$ 5,000,000												9,500,000
Good Start Genetics, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments																								$ 12,000,000
Convertible bridge loan									$ 3,700,000
Hoopla Software, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	25.50%							25.50%				25.50%
Payments to acquire equity method investments																						$ 3,800,000
Convertible bridge loan				$ 1,000,000
Full Measure
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	36.00%							36.00%				36.00%
Payments to acquire equity method investments							$ 4,000,000							$ 4,000,000
WebLinc
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	38.00%							38.00%				38.00%
Payments to acquire equity method investments					$ 4,400,000										$ 6,600,000
Spongecell
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	23.00%							23.00%				23.00%
Payments to acquire equity method investments																					$ 14,000,000
Convertible bridge loan											$ 4,000,000
Syapse, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments					$ 7,500,000											$ 5,800,000
Clutch Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	45.00%							45.00%				45.00%
Payments to acquire equity method investments											$ 4,000,000							$ 12,300,000