Ownership Interests in and Advances to Partner Companies and Funds - Narrative (Detail) - USD ($) $ in Thousands	1 Months Ended						3 Months Ended			9 Months Ended
	Jul. 31, 2015	Apr. 30, 2015	Mar. 31, 2015	Feb. 28, 2014	Jan. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2015	Sep. 30, 2014
Investment [Line Items]
Proceeds from sale of business										$ 25,029	$ 81,626
Alverix, Inc. [Member]
Investment [Line Items]
Proceeds from sale of business					$ 15,700
Gain on sale of business	$ 1,700				$ 15,700
Alverix [Member]
Investment [Line Items]
Proceeds from sale of business	1,700
Thing Worx Inc [Member]
Investment [Line Items]
Proceeds from sale of business	3,300					$ 36,400
Gain on sale of business	3,300
Amount held in escrow							$ 4,100			4,100
Proceeds from milestone payments							3,200
Crescendo Bioscience, Inc. [Member]
Investment [Line Items]
Proceeds from sale of business	900		$ 2,000	$ 38,400
Gain on sale of business	900		$ 2,000
Realized gains on cost method investment				$ 27,400
Quantia [Member]
Investment [Line Items]
Proceeds from sale of business	$ 7,800
Amount held in escrow							1,200			1,200
Asset impairment charges								$ 2,900
Drive Factor [Member]
Investment [Line Items]
Proceeds from sale of business		$ 9,100
Gain on sale of business		$ 6,100
Amount held in escrow							$ 1,100			$ 1,100
InfoBionic [Member]
Investment [Line Items]
Asset impairment charges								$ 3,200
Dabo [Member]
Investment [Line Items]
Asset impairment charges									$ 2,300