Stock-Based Compensation (Details Textual) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Stock based compensation (Textual) [Abstract]
Description of equity modification associated with CFO transition			During May 2015, the Company entered into a separation agreement with its previous chief financial officer that triggered a modification of a portion of his outstanding stock options, RSAs, and Long-Term PBRSUs
Incremental expense associated with equity modification	$ 1.3		$ 1.3
Acceleration of share based compensation expense associated with CFO transition	0.4		0.4
Forfeiture credits associated with CFO transition	$ 0.2		$ 0.2
Stock options [Member]
Stock based compensation (Textual) [Abstract]
Weighted-average grant-date fair value of stock options granted	$ 22.11	$ 17.10	$ 22.11	$ 22.64
Total intrinsic value of stock options exercised	$ 5.1	$ 1.7	$ 12.4	$ 8.5
Total fair value of shares vested	1.1	1.4	2.4	2.1
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	9.7		$ 9.7
Weighted-average remaining period over which cost is expected to be recognized			2 years 4 months 10 days
Restricted stock awards [Member]
Stock based compensation (Textual) [Abstract]
Total fair value of shares vested	18.2	19.8	$ 27.2	28.2
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	49.2		$ 49.2
Weighted-average remaining period over which cost is expected to be recognized			2 years 8 months 10 days
Performance-based restricted stock units [Member]
Stock based compensation (Textual) [Abstract]
Total fair value of shares vested	0.0	$ 0.0	$ 10.6	$ 13.3
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	21.1		$ 21.1
Weighted-average remaining period over which cost is expected to be recognized			10 months 15 days
Performance-based restricted stock units [Member] | Revenue [Member]
Stock based compensation (Textual) [Abstract]
Target number of performance-based restricted stock units granted during the period				149
Award terms				performance conditions based on revenue for the year ending December 31, 2014, 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 target number of shares
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			242	74
Award terms			market conditions based on the Company's total stockholder return ("TSR") relative to that of the Russell 2000 Index over the one-, two-, and three-year periods ending December 31, 2015, 2016, and 2017, respectively, vesting in equal parts upon those dates, and with the number of PBRSUs ultimately earned ranging from zero to 200% of the target number of shares	market conditions based on the Company's TSR relative to that of the NASDAQ Composite Index for the year ending December 31, 2014, 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 target number of shares
Employee stock purchase plan [Member]
Stock based compensation (Textual) [Abstract]
Unrecognized compensation cost related to non-vested stock-based compensation awards granted	$ 3.6		$ 3.6
Weighted-average remaining period over which cost is expected to be recognized			11 months 12 days
Shares issued during period under employee stock purchase plan	86	68	86	68
Weighted-average purchase price of shares issued during period under employee stock purchase plan	$ 37.93	$ 36.39	$ 37.93	$ 36.39