Investments (Detail) (USD $)	3 Months Ended		9 Months Ended					1 Months Ended							1 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Venture Capital Funds	Sep. 30, 2014 Promissory Note	Jan. 31, 2013 Again Faster	Sep. 30, 2014 Again Faster	Dec. 31, 2013 Again Faster	Jan. 31, 2013 Again Faster	Sep. 30, 2014 iGo	Dec. 31, 2013 iGo	Aug. 31, 2013 iGo	May 31, 2014 API	Sep. 30, 2014 API	Sep. 30, 2014 Partnership	Sep. 30, 2014 Securities Loaned or Sold under Agreements to Repurchase
Sales of marketable securities	$ 9,400,000	$ 20,400,000	$ 105,112,000	$ 65,474,000
Derivative liability	212,189,000		212,189,000		240,394,000													19,500,000
Realized loss on financial instrument obligation	(100,000)		(800,000)
Membership interest (as a percent)											40.00%			44.70%
Total cash consideration								4,000,000
Shares acquired (in shares)														1,316,866
Total consideration														5,200,000
Ownership (as a percent)									40.00%	40.00%		46.90%	44.70%		20.60%	20.60%
Number of shares held															11,377,192
Number of shares purchased															1,666,666
Loss on change to equity method at fair value	0	0	568,000	0												600,000
Value of investment	26,871,000		26,871,000									4,200,000
Cost-method investments	28,540,000		28,540,000		25,844,000												25,000,000
Fair value of cost method investments																	23,400,000
Other investments						$ 500,000	$ 3,000,000