Investments (Details 3) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments
Fair value of investments	$ 18,889,000	$ 18,889,000	$ 20,478,000
Payable to former employees	939,000	939,000	941,000
Rollforward of the Company's other investments
Balance at the beginning of the period		20,478,000
Losses on investments		1,267,000	1,233,000	2,996,000
Balance at the end of the period	18,889,000	18,889,000	20,478,000
Employee Investment Funds net of Company's ownership interest
Investments
Fair value of investments	1,265,000	1,265,000	1,218,000
Payable to former employees	900,000	900,000	900,000
Rollforward of the Company's other investments
Balance at the beginning of the period		1,218,000
Losses on investments		(36,000)	(28,000)	(39,000)
Balance at the end of the period	1,265,000	1,265,000	1,218,000
Other investments
Investments
Fair value of investments			2,150,000	1,200,000
Rollforward of the Company's other investments
Balance at the beginning of the period		2,150,000	1,200,000
Purchases of investments		947,000	950,000
Sales / redemptions of investments		(600,000)
Losses on investments		(2,497,000)		847,000
Balance at the end of the period			2,150,000	1,200,000
Amount received on redemption of investment	600,000
Warrants granted on redemption of investments in privately held companies
Investments
Fair value of investments	0	0
Rollforward of the Company's other investments
Balance at the end of the period	$ 0	$ 0
Exercise price of warrants (in dollars per share)	$ 1	$ 1
Warrants granted on redemption of investments in privately held companies | Minimum
Rollforward of the Company's other investments
Ownership interest in investee due to warrant exercise on occurrence of liquidity event (as a percent)	0.40%
Warrants granted on redemption of investments in privately held companies | Maximum
Rollforward of the Company's other investments
Ownership interest in investee due to warrant exercise on occurrence of liquidity event (as a percent)	2.20%