Company Overview, Basis of Presentation, and Summary of Significant Accounting Policies (Details 3) - Significant Accounting Policies (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Goodwill and Intangible Assets
Goodwill impairment recognized	$ 0	$ 0	$ 0
Revenue and Deferred Revenue
Deferred revenue, total	26,500,000
Deferred revenue, current portion	22,868,000	17,265,000
Deferred revenue, non-current portion	3,662,000	3,695,000
Advertising Costs
Advertising expenses	58,900,000	44,700,000	37,800,000
Foreign Currency
Income tax expense allocated to foreign currency translation adjustments	0	0	100,000
Minimum
Prepaid Expenses and Other Assets
Agreement period of software maintenance contracts	1 year
Maximum
Prepaid Expenses and Other Assets
Agreement period of software maintenance contracts	3 years
Stock Options
Share-Based Compensation
Stock options vesting period	4 years
Stock options expiration period	7 years	7 years	7 years
Stock Options | Minimum
Share-Based Compensation
Stock options expiration period	7 years
Stock Options | Maximum
Share-Based Compensation
Stock options expiration period	10 years
Deferred revenue to be amortized to revenue in 2014
Revenue and Deferred Revenue
Deferred revenue, current portion	22,900,000
Deferred revenue to be amortized to revenue in 2015
Revenue and Deferred Revenue
Deferred revenue, non-current portion	3,400,000
Deferred revenue to be amortized to revenue in 2016
Revenue and Deferred Revenue
Deferred revenue, non-current portion	$ 200,000
Equipment | Minimum
Leases and Internally Developed Software
Operating lease terms	2 years
Equipment | Maximum
Leases and Internally Developed Software
Operating lease terms	5 years
Property | Minimum
Leases and Internally Developed Software
Estimated useful lives of assets	2 years
Operating lease terms	1 year
Property | Maximum
Leases and Internally Developed Software
Estimated useful lives of assets	30 years
Operating lease terms	20 years
Software
Leases and Internally Developed Software
Estimated useful lives of assets	36 months
Assets held under capital leases | Equipment | Minimum
Leases and Internally Developed Software
Estimated useful lives of assets	2 years
Assets held under capital leases | Equipment | Maximum
Leases and Internally Developed Software
Estimated useful lives of assets	5 years
Assets held under capital leases | Property
Leases and Internally Developed Software
Estimated useful lives of assets	30 years