Stock Option Plans and Share-Based Compensation-Valuation Assumptions (Details)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.90%	[1]	1.60%	[1]	2.30%	[1]
Dividend yield	0.00%		0.00%		0.00%
Volatility	45.80%	[2]	48.50%	[2]	50.30%	[2]
Expected term	5 years 2 months 12 days	[2]	5 years 2 months 12 days	[2]	5 years 2 months 12 days	[2]
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.20%	[1]	0.50%	[1]	0.40%	[1]
Dividend yield	0.00%		0.00%		0.00%
Volatility	38.50%	[2]	40.20%	[2]	48.50%	[2]
Employee Stock Purchase Plan [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 months	[3]	6 months	[3]	6 months	[3]
Employee Stock Purchase Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	2 years	[3]	2 years	[3]	2 years	[3]

[1] The risk-free interest rate for both stock options and the ESPP is based on the zero-coupon U.S. Treasury rate curve in effect at the time of the option grant or at the beginning of the ESPP offering period.

[2] Expected volatility for both stock options and the ESPP reflects a combination of historical and market-based implied volatility consistent with ASC 718 and SEC Staff Accounting Bulletin 107. We determined that the combination of historical and market-based implied volatility provides a more accurate reflection of our market conditions and is more representative of future stock price trends than employing solely historical volatility.

[3] Represents the period of time that options granted are expected to be outstanding, which is derived from historical data on employee exercise and post-vesting employment termination behavior.