Stock Options, Employee Stock Purchase Plan and Restricted Stock (Details) (USD $)	12 Months Ended								12 Months Ended											0 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011 2003 Stock Option Plan [Member]	Dec. 31, 2013 Amended 2003 Plan [Member]	Dec. 31, 2011 Amended 2003 Plan [Member]	Aug. 07, 2009 Amended 2003 Plan [Member]	May 27, 2005 Amended 2003 Plan [Member]	Dec. 31, 2013 Employee Stock Purchase Plan [Member]	Dec. 31, 2012 Employee Stock Purchase Plan [Member]	Dec. 31, 2011 Employee Stock Purchase Plan [Member]	Dec. 31, 2013 Employee Stock Purchase Plan [Member] Minimum [Member]	Dec. 31, 2013 Employee Stock Purchase Plan [Member] Maximum [Member]	Dec. 31, 2013 Stock Options [Member]	Dec. 31, 2012 Stock Options [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2013 Restricted Stock [Member]	Dec. 31, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	May 04, 2013 Restricted Stock [Member] Director [Member]	Dec. 31, 2012 Restricted Stock [Member] Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock approved for issuance (in shares)						19,000,000	11,000,000	5,000,000	2,000,000
Increase in common stock approved for issuance (in shares)						8,000,000
Vesting period														3 years
Expiration period														5 years
Stock-based compensation expense	$ 7,050,000	$ 7,032,000	$ 5,159,000						$ 200,000	$ 200,000	$ 200,000			$ 6,200,000	$ 6,400,000	$ 4,900,000	$ 600,000	$ 400,000	$ 100,000
Assumptions used in estimating fair value of stock options granted [Abstract]
Expected Volatility, minimum ( in hundredths)														49.00%	77.00%	75.00%
Expected Volatility, maximum ( in hundredths)														68.00%	85.00%	76.00%
Expected Life (in years)														4 years	4 years	3 years 9 months 18 days
Risk-free interest rate, minimum (in hundredths)														0.70%	0.70%	1.30%
Risk-free interest rate, maximum (in hundredths)														1.40%	0.80%	2.00%
Dividend yield (in hundredths)														0.00%	0.00%	0.00%
Fair value per stock option (in dollars per share)														$ 6.95	$ 7.76	$ 3.71
Number of Shares [Roll Forward]
Outstanding, beginning balance (in shares)														9,727,000	9,399,000	7,960,000
Granted (in shares)				2,519,000	15,828,000									321,000	1,221,000	2,030,000
Exercised (in shares)					2,304,000									(630,000)	(806,000)	(454,000)
Forfeited (in shares)					4,296,000									(190,000)	(87,000)	(137,000)
Outstanding, ending balance (in shares)														9,228,000	9,727,000	9,399,000
Exercisable, ending balance (in shares)														7,594,000
Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning balance (in dollars per share)														$ 4.22	$ 2.89	$ 1.87
Granted (in dollars per share)														$ 15.76	$ 12.96	$ 6.63
Exercised (in dollars per share)														$ 4.18	$ 1.87	$ 1.93
Forfeited (in dollars per share)														$ 13.10	$ 4.42	$ 2.30
Outstanding, ending balance (in dollars per share)														$ 4.45	$ 4.22	$ 2.89
Exercisable, end of period (in dollars per share)														$ 3.02
Outstanding Options, Weighted Average Remaining Contractual Term														1 year 7 months 10 days
Exercisable Options, Weighted Average Remaining Contractual Term														1 year 3 months 7 days
Outstanding Options, Aggregate Intrinsic Value														186,169,000
Exercisable Options, Aggregate Intrinsic Value														164,018,000
Total intrinsic value of stock options exercised														8,900,000	9,100,000	3,100,000
Additional paid in capital for stock options exercised														2,600,000	1,500,000	900,000
Unrecognized compensation cost related to non-vested stock options														8,251,000
Weighted-average recognition period for unrecognized compensation cost														2 years 4 months 24 days
Value of restricted stock awards granted	579,000	351,000	17,000																	500,000	500,000
Non-vested restricted stock activity, Number of Shares [Roll Forward]
Non-vested beginning of period (in shares)																	18,000	13,000	28,000
Granted (in shares)																	32,000	35,000	0	32,000	35,000
Vested (in shares)																	(34,000)	(30,000)	(15,000)
Canceled (in shares)																	0	0	0
Non-vested end of period (in shares)																	16,000	18,000	13,000
Non-vested restricted stock activity, Weighted Average Grant Date Fair Value [Roll Forward]
Non-vested beginning of period (in dollars per share)																	$ 14.63	$ 1.34	$ 1.89
Granted (in dollars per share)																	$ 15.36	$ 14.63	$ 0
Vested (in dollars per share)																	$ 14.98	$ 9.09	$ 2.34
Canceled (in dollars per share)																	$ 0	$ 0	$ 0
Non-vested end of period (in dollars per share)																	$ 15.36	$ 14.63	$ 1.34
Percentage of base wages withheld for the purchase of stock (in hundredths)												1.00%	15.00%
Annual purchase of stock per employee													25,000
Base wages subject to withholding towards stock purchase													$ 21,250
Percentage of discount on shares purchased (in hundredths)									15.00%
Shares issued under ESPP ( in shares)									1,353,407
Employee stock purchase plan issuances (in shares)									73,000	61,000	71,000
ESPP Shares available for future issuance (in shares)									646,593