Summary of Significant Accounting Policies (Potentially Dilutive Common Shares Excluded from Computation of Weighted-Average Shares Outstanding) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Redeemable convertible preferred stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive common shares excluded from the computation of weighted-average shares outstanding			2,162
Options outstanding [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive common shares excluded from the computation of weighted-average shares outstanding	3,805	3,331	3,894
RSUs [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive common shares excluded from the computation of weighted-average shares outstanding	990	1,398	384
Unvested restricted shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive common shares excluded from the computation of weighted-average shares outstanding			36
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive common shares excluded from the computation of weighted-average shares outstanding	28	28	34