Balance Sheet Detail (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of prepaid expenses and other assets
Deferred commission	$ 7,370,000	$ 7,471,000
Prepaid royalty	1,081,000	1,121,000
Prepaid contract expense	9,798,000	8,858,000
Other	7,619,000	6,210,000
Total prepaid expenses and other assets	25,868,000	23,660,000
Summary of property and equipment, net
Property and equipment, gross	103,257,000	97,454,000
Accumulated depreciation	(65,988,000)	(55,153,000)
Property and equipment, net	37,269,000	42,301,000
Depreciation	11,800,000	11,000,000	10,000,000
Costs related to development of internal use software capitalized during the period	1,600,000	1,300,000	700,000
Computer equipment - hardware
Summary of property and equipment, net
Property and equipment, gross	29,027,000	27,359,000
Computer equipment - software
Summary of property and equipment, net
Property and equipment, gross	27,121,000	25,092,000
Leasehold improvements
Summary of property and equipment, net
Property and equipment, gross	35,801,000	34,371,000
Furniture and fixtures
Summary of property and equipment, net
Property and equipment, gross	9,578,000	9,001,000
Construction in process
Summary of property and equipment, net
Property and equipment, gross	$ 1,730,000	$ 1,631,000