Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2012

Stock-Based Compensation

Schedule of weighted-average fair values and assumptions used in calculation of fair value of stock options and employee stock purchase plan

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2012			2011			2012			2011
Expected volatility:
Stock options	45		%	46		%	46		%	47		%
ESPP	38		%	—		%	43		%	—		%
Risk-free interest rate:
Stock options	1.43		%	1.44		%	1.23		%	2.28		%
ESPP	0.12		%	—		%	0.08		%	—		%
Expected life in years:
Stock options	6.68			5.41			6.98			6.18
ESPP	0.50			—			0.50			—
Weighted-average fair value:
Stock options	$	18.40		$	11.56		$	14.51		$	11.19
ESPP	$	8.12		$	—		$	7.59		$	—