Segment Reporting - Active Partner Companies by Segment (Detail)	Sep. 30, 2019
Aktana, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	17.90%
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%
InfoBionic
Schedule of Equity Method Investments [Line Items]
Ownership interest under equity method, percentage	25.20%
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	32.70%
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	24.20%
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	20.10%
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	37.70%