PROPERTY, EQUIPMENT AND LEASEHOLD IMPROVEMENTS (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, equipment and leasehold improvements
Total	$ 228,498	$ 212,797
Accumulated depreciation and amortization	(169,663)	(150,850)
Property, equipment and leasehold improvements less accumulated depreciation and amortization	58,835	61,947
Depreciation and amortization expense	20,207	21,476	21,235
Software, including software development costs
Property, equipment and leasehold improvements
Total	122,252	110,402
Computer equipment
Property, equipment and leasehold improvements
Total	36,890	34,314
Leasehold improvements
Property, equipment and leasehold improvements
Total	38,152	37,925
Communications equipment
Property, equipment and leasehold improvements
Total	20,125	19,528
Furniture and fixtures
Property, equipment and leasehold improvements
Total	10,350	9,911
Automobiles
Property, equipment and leasehold improvements
Total	$ 729	$ 717