Stock-Based Compensation (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
2009 Long-Term Incentive Plan [Member]
Stock based compensation (Textual) [Abstract]
Increase in number of shares authorized under share based compensation plan	1,500,000
Number of shares of common stock issuable under share based compensation plan as amended	5,500,000
Stock options [Member]
Stock based compensation (Textual) [Abstract]
Weighted-average grant-date fair value of stock options granted	$ 0.00	$ 8.89
Total intrinsic value of stock options exercised	$ 4.4	$ 5.7
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	7.7
Weighted-average remaining period over which cost is expected to be recognized	2 years 7 months 28 days
Total fair value of shares vested	0.9	0.9
Restricted stock awards [Member]
Stock based compensation (Textual) [Abstract]
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	36.0
Weighted-average remaining period over which cost is expected to be recognized	2 years 8 months 9 days
Total fair value of shares vested	0.2	0.1
Performance based restricted stock units [Member]
Stock based compensation (Textual) [Abstract]
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	$ 24.2
Weighted-average remaining period over which cost is expected to be recognized	2 years 9 months 19 days
Performance based restricted stock units [Member] | Revenue and Minimum Profitability [Member]
Stock based compensation (Textual) [Abstract]
Target number of performance based restricted stock units granted during the period	113,538
Award terms	based on revenue for the year ending December 31, 2013 relative to the Company's revenue guidance and a minimum profitability condition, vesting annually over three years commencing on the first anniversary of the grant date, with the number of PBRSUs ultimately earned ranging from zero to 200% of the original award
Performance based restricted stock units [Member] | TSR [Member]
Stock based compensation (Textual) [Abstract]
Target number of performance based restricted stock units granted during the period	56,769
Award terms	based on the Company's total stockholder return ("TSR") relative to that of the NASDAQ Composite Index for the year ending December 31, 2013, vesting annually over three years commencing on the first anniversary of the grant date, with the number of PBRSUs ultimately earned ranging from zero to 200% of the original award
Performance based restricted stock units [Member] | CAGR [Member]
Stock based compensation (Textual) [Abstract]
Target number of performance based restricted stock units granted during the period	305,414
Award terms	based on the Company's compound annual growth rate of revenue ("CAGR"), as defined in the grant agreement, and the Company's absolute TSR over the three-year performance period ending December 31, 2015, vesting in full on December 31, 2015, with the number of PBRSUs ultimately earned ranging from zero to 300% of the original award