Segment Reporting - Active Partner Companies by Segment (Detail)	Mar. 31, 2018
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	29.30%
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	31.20%
CloudMine
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	47.30%
Clutch Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	41.30%
Flashtalking
Schedule of Equity Method Investments [Line Items]
Ownership interest under cost method, percentage	10.30%
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	20.50%
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	28.70%
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%
T-REX Group, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	21.10%
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	24.60%
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	36.20%
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	20.10%
Healthcare | Trice
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	24.80%
Healthcare | Zipnosis
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	25.40%