Stockholders' Equity (Details 4) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Employee and non-employee stock option exercise data
Number of options exercised (in shares)	345,664	445,955	597,499	717,197
Cash received	$ 14,314	$ 13,736	$ 24,445	$ 22,171