Stock Option and Purchase Plans (Details) (USD $)		12 Months Ended		1 Months Ended	0 Months Ended	12 Months Ended
	Mar. 29, 2010 2001 Stock Option Plan	Dec. 31, 2012 2010 Equity Incentive Plan	Jun. 25, 2010 2010 Equity Incentive Plan	Apr. 30, 2010 Stand-Alone Stock Option Agreement	Jan. 25, 2013 Stock options	Dec. 31, 2012 Stock options	Dec. 31, 2011 Stock options	Dec. 31, 2010 Stock options	Dec. 31, 2012 Restricted stock units Y
Stock Option and Purchase Plans
Shares reserved and unissued	32,000					4,745,966
Expiration period of awards granted (in years)						P10Y
Vesting period (in years)		4 years
Number of shares authorized			8,400,000
Number of shares reserved but not issued pursuant to awards under 2001 Stock Option Plan			99,975
Number of shares reserved but not issued pursuant to options outstanding under 2001 Stock Option Plan			8,111,273
Number of Restricted Stock Units
Granted (in shares)									35,000
Restricted stock units outstanding at the end of the period (in shares)									35,000
Weighted Average Grant Date Fair Value
Granted (in dollars per share)									$ 24.88
Restricted stock units outstanding at the end of the period (in dollars per shares)									$ 24.88
Weighted Average Remaining Contractual Term (Years)
Weighted Average Remaining Contractual Term									1.22
Aggregate Intrinsic Value
Aggregate Intrinsic Value (in dollars)									$ 469,700
Number of Shares
Balance at beginning of year (in shares)						8,575,434	7,919,013	7,553,776
Granted (in shares)		1,289,790		400,000	1,928,132	2,850,118	1,289,790	1,729,135	35,000
Exercised (in shares)						(2,648,882)	(482,172)	(982,594)
Cancelled (in shares)						(265,753)	(151,197)	(381,304)
Balance at end of year (in shares)						8,510,917	8,575,434	7,919,013
Exercisable at end of year (in shares)						4,781,301	6,120,210	5,171,827
Weighted-Average Exercise Price
Balance at beginning of year (in dollars per share)						$ 6.17	$ 5.71	$ 4.74
Granted (in dollars per share)						$ 17.80	$ 8.72	$ 9.37
Exercised (in dollars per share)						$ 5.00	$ 4.88	$ 4.34
Cancelled (in dollars per share)						$ 9.28	$ 8.32	$ 6.66
Balance at end of year (in dollars per share)						$ 10.33	$ 6.17	$ 5.71
Exercisable at end of year (in dollars per share)						$ 6.32	$ 5.38	$ 4.82
Weighted average grant-date fair value of options granted during the year (in dollars per share)						$ 11.91	$ 5.91	$ 5.74