Stockholders' Equity (Details 4) (Employee Stock [Member]) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Employee Stock [Member]
Employee Stock Purchase Plan
Outstanding and exercisable, beginning of period	626,480	576,660	392,517	335,608
Granted			261,960	256,080
Exercised	(2,654)	(2,074)	(7,245)	(5,442)
Forfeited	(9,376)	(7,819)	(32,782)	(19,479)
Expired	(166,207)	(136,536)	(166,207)	(136,536)
Outstanding and exercisable, end of period	448,243	430,231	448,243	430,231