Strategic Agreement With Ally (Details) (USD $)	1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	May 31, 2010	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011 Ally Financial [Member]	Sep. 30, 2010 Ally Financial [Member]	Sep. 30, 2011 Ally Financial [Member]	Sep. 30, 2010 Ally Financial [Member]	Dec. 31, 2010 Ally Financial [Member]
Payment for financing option	$ 15,000,000
Contra revenue from strategic agreement				800,000	600,000	2,400,000	800,000
Prepaid expenses and other current assets		25,092,000	17,929,000	3,200,000		3,200,000		3,200,000
Other long-term assets		13,949,000	12,118,000	7,800,000		7,800,000		10,200,000
Unamortized payment for financing option						$ 11,000,000		$ 13,400,000