Stockholders' Equity (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended										1 Months Ended	12 Months Ended	1 Months Ended			0 Months Ended	12 Months Ended				1 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Stock options	Dec. 31, 2012 Stock options	Dec. 31, 2011 Stock options	Dec. 31, 2013 Market-based Restricted Stock Units	Dec. 31, 2012 Market-based Restricted Stock Units	Dec. 31, 2013 Market-based Restricted Stock Units Minimum	Dec. 31, 2013 Market-based Restricted Stock Units Maximum	Sep. 30, 2013 Service-based Restricted Stock Units	Dec. 31, 2013 Service-based Restricted Stock Units	Sep. 30, 2013 Service-based Restricted Stock Units Vesting over the first year	Sep. 30, 2013 Service-based Restricted Stock Units Vesting over the second year	Sep. 30, 2013 Service-based Restricted Stock Units Vesting over the third year	May 07, 2013 Employee Stock Purchase Plan item	Dec. 31, 2013 Employee Stock Purchase Plan	Dec. 31, 2013 2002 Plan Stock options	Dec. 31, 2013 2002 Plan Stock options Minimum	Dec. 31, 2013 2006 Plan Stock options	Sep. 30, 2013 CERF Plan Stock options	Dec. 31, 2013 CERF Plan Stock options
Summary of stock-based compensation expense
Stock-based compensation expense	$ 23,008	$ 22,087	$ 13,473	$ 13,751	$ 14,199	$ 13,473	$ 8,821	$ 7,888				$ 51					$ 29					$ 356
Stock-based compensation expense, net of tax	23,008	22,087	13,473
Expiration term																		10 years
Purchase price of options expressed as percentage of fair market value of common stock																85.00%			100.00%
Purchase price of options granted to 10% stockholders expressed as percentage of fair market value of common stock																			110.00%
Percentage ownership of stock for which the option purchase price will be 110% of fair market																		10.00%
Vesting period											3 years							3 years
Number of shares reserved for issuance																				17,890,500	150,000
Number of shares available for future grant																				1,428,209
Vesting percentage													34.00%	33.00%	33.00%
Number of shares reserved																2,500,000
Shares sold pursuant to the ESPP																	14,934
Number of Shares / Units
Outstanding at the beginning of the period				12,083,677
Options granted				98,500																		115,000
Options exercised				(119,349)
Options forfeited				(535,830)
Outstanding at the end of the period				11,526,998	12,083,677																	115,000
Exercisable at the end of the period				9,597,193
Weighted Average Exercise Price
Outstanding at the beginning of the period				$ 11.75
Options granted				$ 13.47																		$ 40.80
Options exercised				$ 5.24
Options forfeited				$ 12.64
Outstanding at the end of the period				$ 11.79	$ 11.75																	$ 40.80
Exercisable at the end of the period				$ 11.39
Additional option disclosures
Options outstanding at the end of the period, weighted average remaining contractual term				5 years 6 months 4 days																		9 years 8 months 19 days
Options exercisable at the end of the period, weighted average remaining contractual term				4 years 11 months 1 day
Options outstanding at the end of the period, aggregate intrinsic value				12,564
Options exercisable at the end of the period, aggregate intrinsic value				14,300
Weighted-average assumption used for grants
Dividend yield				0.00%																		0.00%
Expected volatility, minimum				51.00%
Expected volatility, maximum				55.60%
Expected volatility																						96.40%
Risk-free interest rate, minimum				1.00%
Risk-free interest rate, maximum				1.90%
Risk-free interest rate																						1.90%
Expected life				6 years																		6 years
Number of Shares
Outstanding at the beginning of the period							1,545,000
RSUs granted												45,836
Outstanding and non-vested at the end of the period							1,545,000	1,545,000				45,836
Weighted Average Fair Value at Grant Date
Outstanding at the beginning of the period							$ 11.32
RSUs granted												$ 13.09
Outstanding and non-vested at the end of the period							$ 11.32	$ 11.32				$ 13.09
Other disclosures
Weighted Average Remaining Contractual Term							2 years 1 month 6 days					2 years 8 months 12 days
Total unrecognized compensation cost related to non-vested shares				11,530
Total unrecognized compensation cost related to non-vested shares							933					549										3,310
Weighted average period over which the total unrecognized compensation cost related to non-vested units is expected to be recognized				1 year 3 months 18 days			1 month 6 days					2 years 8 months 12 days										1 year 9 months 25 days
Total fair value of shares vested				16,305
Intrinsic value of all options exercised				$ 935	$ 18,822	$ 1,626
Number of shares of common stock to be received for each performance unit							1
Period from the date of grant in which the closing price of the entity's common stock must exceed the closing price in order for a holder to receive one share of common stock for each award									2 years	4 years
Number of consecutive trading days during which the closing price of the entity's common stock must exceed the closing price on the grant date in order for a holder to receive one share of common stock for each award							20 days
Period from the date of grant after which awards will be automatically forfeited if the Stock Price Condition is not satisfied							4 years
Percentage of the closing price of the entity's common stock that the closing price must equal or exceed in order for an award holder to receive one share of common stock for each award							135.00%
Weighted-average grant date fair values of options granted				$ 6.86	$ 7.95	$ 8.98															$ 31.65
Number of non-concurrent offering periods																2