Stockholders' Equity (Details 4) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Employee and non-employee stock option exercise data
Number of options exercised (in shares)	460,600	310,673	1,177,797	665,363
Cash received	$ 17,220	$ 9,799	$ 39,391	$ 19,896