Stockholders' Equity (Details 4) (Employee Stock [Member])	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Employee Stock [Member]
Summary of the Employee Stock Purchase Plan activity
Outstanding and exercisable, beginning of period	712,385	626,480	425,196	392,517
Granted	0	0	327,936	261,960
Exercised	(8,787)	(2,654)	(21,368)	(7,245)
Forfeited	(23,547)	(9,376)	(51,713)	(32,782)
Expired	(182,315)	(166,207)	(182,315)	(166,207)
Outstanding and exercisable, end of period	497,736	448,243	497,736	448,243