Segment Reporting - Active Partner Companies by Segment (Detail)	Mar. 31, 2019
Aktana, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	18.90%
Clutch Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	41.20%
Flashtalking
Schedule of Equity Method Investments [Line Items]
Ownership interest under cost method, percentage	10.10%
Hoopla Software, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	25.50%
InfoBionic
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	25.40%
Lumesis, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	43.60%
MediaMath, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under cost method, percentage	13.40%
meQuilibrium
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	33.10%
Moxe Health
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	32.40%
Novasom, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	31.70%
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	24.20%
Sonobi
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	21.60%
Syapse, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	20.00%
T-REX Group, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	17.80%
Transactis
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	23.60%
Trice
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	16.70%
WebLinc
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	38.50%
Zipnosis
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	34.70%