Financial Instruments (Details 3) (USD $) In Thousands, unless otherwise specified					3 Months Ended					3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Investments Level 3	Dec. 31, 2012 Investments Level 3	Mar. 31, 2013 Investments Level 3 Market comparable companies Minimum	Mar. 31, 2013 Investments Level 3 Market comparable companies Maximum	Mar. 31, 2013 Investments Level 3 Market comparable companies Weighted average	Mar. 31, 2013 Investment in FATV	Dec. 31, 2012 Investment in FATV	Mar. 31, 2013 Investment in FATV Level 3 item
Disclosure About Significant Unobservable Inputs
Investments	$ 21,597	$ 20,478	$ 21,597	$ 20,478				$ 17,251	$ 17,110	$ 17,300
Number of holdings										19
Number of privately held companies										7
Enterprise value/Revenue multiple					1.5	6.7	5.9
Discount rate (as a percent)					0.00%	40.00%	27.00%