Ownership Interests in and Advances to Partner Companies and Funds - Narrative (Detail) - USD ($)	1 Months Ended				3 Months Ended		6 Months Ended
	Jun. 30, 2016	Apr. 30, 2016	Jan. 31, 2016	Apr. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Apr. 30, 2017	Jul. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Equity method investments	$ 158,439,000				$ 158,439,000		$ 158,439,000				$ 151,840,000
Proceeds from sale of business							72,824,000	$ 11,379,000
Revenue							13,298,000	11,080,000
Gross profit							12,917,000	10,564,000
Net income (loss)							13,721,000	(415,000)
AppFirst, Inc.
Investment [Line Items]
Asset Impairment Charges					1,700,000		1,700,000
Equity method investments	0				0		0
Proceeds from sale of business	900,000
Bridgevine Inc [Member]
Investment [Line Items]
Proceeds from sale of business	$ 5,000,000
Gain on sale of business					400,000		500,000
Putney, Inc.
Investment [Line Items]
Proceeds from sale of business		$ 58,200,000
Gain on sale of business					55,200,000		55,200,000
Drive Factor [Member]
Investment [Line Items]
Proceeds from sale of business		1,100,000		$ 9,100,000
Gain on sale of business					$ 1,100,000	$ 6,100,000	1,100,000	$ 0
Thing Worx Inc
Investment [Line Items]
Proceeds from sale of business		$ 3,300,000	$ 4,100,000
Gain on sale of business							$ 3,300,000
Scenario, Forecast [Member] | Putney, Inc.
Investment [Line Items]
Amount held in escrow									$ 600,000	$ 400,000