Ownership Interests in and Advances to Partner Companies and Funds - Narrative (Detail) - USD ($) $ in Thousands	1 Months Ended					3 Months Ended
	Mar. 31, 2017	Jan. 31, 2017	Jul. 31, 2016	Apr. 30, 2016	Jul. 31, 2015	Mar. 31, 2017	Mar. 31, 2016	Mar. 03, 2017	Dec. 31, 2016
Investment [Line Items]
Proceeds from sale of business						$ 15,753	$ 4,194
Equity method investments	$ 132,298					132,298			$ 154,666
Pneuron
Investment [Line Items]
Asset Impairment Charges						2,700
Equity method investments	2,500					2,500
Beyond.com, Inc
Investment [Line Items]
Consideration received per transaction	26,000
Proceeds from sale of business	$ 15,500
Term of note receivable (in years)	3 years
Amount of consideration received	$ 10,500
Interest rate on note receivable								9.50%
Gain on sale of business						100
Quantia, Inc.
Investment [Line Items]
Proceeds from sale of business		$ 600	$ 600		$ 7,800
Gain on sale of business						$ 600
Thing Worx, Inc.
Investment [Line Items]
Proceeds from sale of business				$ 3,300
Gain on sale of business							$ 3,300