Segment Reporting - Active Partner Companies by Segment (Detail)	Sep. 30, 2017
AdvantEdge Healthcare Solutions, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	40.10%
Apprenda
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	29.40%
BrickWork
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	20.30%
Cask Data
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	31.30%
CloudMine
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	47.40%
Clutch Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	42.70%
Full Measure
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	42.30%
Hoopla Software, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	25.50%
Lumesis, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	43.80%
MediaMath, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	20.40%
Moxe Health
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	32.40%
Prognos
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	35.20%
QuanticMind, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	24.70%
Sonobi
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	21.60%
Spongecell
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	23.00%
T-REX Group, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	21.30%
Transactis
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	23.80%
WebLinc
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	38.00%
Healthcare | Aktana, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	24.50%
Healthcare | InfoBionic
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	39.50%
Healthcare | meQuilibrium
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	37.00%
Healthcare | Novasom, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	31.70%
Healthcare | Propeller
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	24.00%
Healthcare | Syapse, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	26.00%
Healthcare | Trice
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	24.90%
Healthcare | Zipnosis
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	25.40%