SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Significant Accounting Policies [Line Items]
Restricted cash	$ 700,000		$ 700,000		$ 400,000
Unbilled revenue within accounts receivable	9,700,000		9,700,000		6,600,000
Provision for doubtful accounts	200,000	200,000	576,000	378,000
Write-offs of doubtful accounts	100,000	100,000	400,000	300,000
Finite lived intangible assets useful life, minimum			1
Finite lived intangible assets useful life, maximum			20
Property and equipment, accumulated depreciation	124,000,000		124,000,000		108,800,000
Capitalized software development costs	3,900,000	4,000,000	7,600,000	7,500,000
Capitalized software depreciation expense	3,000,000	2,400,000	5,800,000	4,700,000
Investment accounted for under cost method investment	1,000,000		1,000,000
Repurchase and retirement of common stock, shares			1,202,874	1,469,900
Repurchase and retirement of common stock, value			10,269,000	11,100,000
Redeemed shares related to share-based compensation			155,985	145,078
Payments related to tax withholding for share-based compensation			1,200,000	1,100,000
Preferred Stock, shares authorized	5,000,000		5,000,000
Preferred Stock, par value per share	$ 0.01		$ 0.01
Income tax expense	2,739,000	1,911,000	5,763,000	3,741,000
Unrecognized tax benefits	4,100,000		4,100,000		3,400,000
Unrecognized tax benefits that would affect effective tax rate, if recognized	2,700,000		2,700,000		2,500,000
Reserve for Sales and Excise Tax [Member]
Significant Accounting Policies [Line Items]
Valuation allowances and reserves	2,000,000		2,000,000		1,700,000
Foreign and State Net Operating Loss and Capital Loss Carryforwards [Member]
Significant Accounting Policies [Line Items]
Increase in valuation allowance			300,000
Accumulated Other Comprehensive Income (Loss) [Member]
Significant Accounting Policies [Line Items]
Repurchase and retirement of common stock, value
Furniture And Fixtures [Member]
Significant Accounting Policies [Line Items]
Tangible assets estimated useful life, minimum			5
Tangible assets estimated useful life, maximum			7
Software [Member]
Significant Accounting Policies [Line Items]
Finite lived intangible assets useful life, minimum			2
Finite lived intangible assets useful life, maximum			5
Computer Servers, Internet And Telecommunications [Member]
Significant Accounting Policies [Line Items]
Tangible assets estimated useful life, minimum			3
Tangible assets estimated useful life, maximum			10