Operating Segments - Active Partner Companies by Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Operating loss	$ (4,485)		$ (4,177)	$ (5,069)	$ (5,239)	$ (4,720)	$ (4,835)	$ (6,715)	$ (5,374)	$ (18,970)		$ (21,644)	$ (19,473)
Other income (loss), net	77		(246)	1,452	30,374	6,574	(4,224)	(2,724)	757	31,657		383	9,338
Interest income	407		482	542	470	550	572	790	734	1,901		2,646	2,926
Equity loss	(10,006)		(8,962)	(3,175)	6,808	22,646	(9,866)	(18,400)	(6,987)	(15,335)		(12,607)	(26,517)
Net loss	(15,114)		(14,006)	(7,348)	31,319	23,967	(19,430)	(28,123)	(11,939)	(5,149)		(35,525)	(39,362)
Assets	318,454					345,996				318,454		345,996
Net loss before income taxes	(15,114)		(14,006)	(7,348)	31,319	23,967	(19,430)	(28,123)	(11,939)	(5,149)		(35,525)	(39,362)
Income tax benefit (expense)	0		0	0	0	0	0	0	0	0		0	0
Healthcare [Member]
Schedule of Equity Method Investments [Line Items]
Operating loss										0		0	0
Other income (loss), net										31,820		(857)	19,884
Interest income										0		0	0
Equity loss										(3,944)		(31,706)	(26,544)
Net loss										27,876		(32,563)	(6,660)
Assets	62,292					74,939				62,292		74,939
Healthcare [Member] | AdvantEdge Healthcare Solutions, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	40.10%					40.10%				40.10%		40.10%	40.20%
Healthcare [Member] | Dabo Health, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under cost method, percentage	15.30%					8.00%				15.30%		8.00%
Healthcare [Member] | Good Start Genetics, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	29.90%					30.00%				29.90%		30.00%	30.00%
Healthcare [Member] | InfoBionic [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	27.80%									27.80%
Healthcare [Member] | Medivo, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	34.50%					34.50%				34.50%		34.50%	30.00%
Healthcare [Member] | NovaSom, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	31.70%					30.30%				31.70%		30.30%	30.30%
Healthcare [Member] | Propeller [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	24.60%									24.60%
Healthcare [Member] | Putney, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	28.30%					27.60%				28.30%		27.60%	27.60%
Healthcare [Member] | Quantia, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	42.30%					35.10%				42.30%		35.10%
Healthcare [Member] | Syapse, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	27.00%									27.00%
Healthcare [Member] | Trice [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	31.90%									31.90%
Technology [Member]
Schedule of Equity Method Investments [Line Items]
Operating loss										0		0	0
Other income (loss), net										0		0	0
Interest income										0		0	0
Equity loss										(10,831)		20,899	(119)
Net loss										(10,831)		20,899	(119)
Assets	88,408					69,471				88,408		69,471
Technology [Member] | Appfirst [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	34.30%					34.30%				34.30%		34.30%	35.00%
Technology [Member] | Apprenda, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	21.60%					22.00%				21.60%		22.00%
Technology [Member] | Beyond.com, Inc [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	38.20%					38.20%				38.20%		38.20%	38.30%
Technology [Member] | Bridgevine, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under cost method, percentage	17.20%	[1]				22.70%				17.20%	[1]	22.70%	21.70%
Technology [Member] | Clutch [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	29.60%					24.00%				29.60%		24.00%
Technology [Member] | DriveFactor Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	40.60%					40.60%				40.60%		40.60%	35.40%
Technology [Member] | Hoopla Software, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	25.60%					25.30%				25.60%		25.30%	25.30%
Technology [Member] | Lumesis, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	45.70%					44.20%				45.70%		44.20%	31.60%
Technology [Member] | MediaMath, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	20.70%					22.50%				20.70%		22.50%	22.20%
Technology [Member] | Pneuron [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	27.60%					27.60%				27.60%		27.60%
Technology [Member] | Spongecell, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	23.00%					23.00%				23.00%		23.00%	23.10%
Technology [Member] | Transactis [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	24.80%									24.80%
Technology [Member] | WebLinc [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	29.20%									29.20%
Reportable Subsegments [Member]
Schedule of Equity Method Investments [Line Items]
Operating loss										0		0	0
Other income (loss), net										31,820		(857)	19,884
Interest income										0		0	0
Equity loss										(14,775)		(10,807)	(26,663)
Net loss										17,045		(11,664)	(6,779)
Assets	150,700					144,410				150,700		144,410
Other Segments [Member]
Schedule of Equity Method Investments [Line Items]
Operating loss										(18,970)		(21,644)	(19,473)
Other income (loss), net										(163)		1,240	(10,546)
Interest income										1,901		2,646	2,926
Equity loss										(560)		(1,800)	146
Net loss										(22,194)		(23,861)	(32,583)
Assets	167,754					201,586				167,754		201,586
Net loss before income taxes										(22,194)		(23,861)	(32,583)
Income tax benefit (expense)										$ 0		$ 0	$ 0

[1] (1) In the second quarter of 2014, the Company’s ownership interest in Bridgevine decreased from 22.7% to 17.3%, below thethreshold at which the Company believes it exercises significant influence. Accordingly, the Company changed its method ofaccounting for Bridgevine from the equity method to the cost method.