Strategic Agreement with Ally (Details) (USD $)	1 Months Ended			3 Months Ended		6 Months Ended		12 Months Ended
	May 31, 2010	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Ally Financial [Member]	Jun. 30, 2010 Ally Financial [Member]	Jun. 30, 2011 Ally Financial [Member]	Jun. 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	200,000	1,600,000	200,000
Prepaid Expenses And Other Assets Current		27,693,000	17,929,000	3,200,000		3,200,000		3,200,000
Other long-term assets		12,409,000	12,118,000	8,600,000		8,600,000		10,200,000
Unamortized Payment for Financing Option						$ 11,800,000		$ 13,400,000