SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended						3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013 Investment in Cloud Solutions Provider [Member]	Sep. 30, 2012 Investment in Cloud Service Marketplace Company [Member]	Jun. 30, 2011 Investment in Conferencing Company [Member]	Mar. 31, 2013 Furniture and Fixtures [Member] Minimum [Member]	Mar. 31, 2013 Furniture and Fixtures [Member] Maximum [Member]	Mar. 31, 2013 Software [Member] Minimum [Member]	Mar. 31, 2013 Software [Member] Maximum [Member]	Mar. 31, 2013 Computer, communication and network equipment [Member] Minimum [Member]	Mar. 31, 2013 Computer, communication and network equipment [Member] Maximum [Member]
Significant Accounting Policies [Line Items]
Restricted cash	$ 0		$ 600
Unbilled revenue within accounts receivable	10,200		6,700
Provision for doubtful accounts	(31)	357
Write-offs of doubtful accounts	100	300
Property and equipment, estimated useful life							5 years	7 years	2 years	5 years	3 years	10 years
Property and equipment, accumulated depreciation	140,600		134,200
Capitalized software development costs	3,800		3,600
Capitalized software depreciation expense	3,200	2,800
Investment accounted for under cost method investment	2,800		1,900	1,000	1,000	1,000
Interest earned on cost method investment	8.00%
Stock repurchase program, shares repurchased	242,200
Stock repurchase program, value of shares repurchased	2,200
Shares withheld in satisfaction of employee tax withholding obligations	109,763	94,783
Amount remitted related to tax withholding for share-based compensation	1,100	800
Preferred stock, shares authorized	5,000,000
Preferred stock, par or stated value per share	$ 0.01
State excise and sales tax reserve	2,100		2,000
Income tax expense	2,640	3,024
Unrecognized tax benefits	5,700		5,400
Unrecognized tax benefits that would affect effective tax rate, if recognized	4,400		4,100
Increase in valuation allowance	$ 200