Commitments and Contingencies - Capital Leases (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Capital Leased Assets [Line Items]
Marketable debt securities collateral	$ 3,200,000	$ 3,300,000
Commitments under capital leases [Abstract]
Capital lease obligations	1,300,000	2,500,000
Equipment
Commitments under capital leases [Abstract]
2013	1,255,000
2014	130,000
Total	1,385,000
Less: amount representing interest	(76,000)
Total	$ 1,309,000