Summary of Significant Accounting Policies and Basis of Presentation - Property and Equipment (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 6.2	$ 8.2	$ 7.1
Computer laptops [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Computer desktops [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	4 years
IT server, storage and network equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Purchased software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	10 years