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ACQUISITIONS (Income Statement) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Revenues									$ 730,027us-gaap_Revenues	$ 555,117us-gaap_Revenues	$ 433,799us-gaap_Revenues
Net income	18,423us-gaap_NetIncomeLoss	19,040us-gaap_NetIncomeLoss	14,814us-gaap_NetIncomeLoss	17,364us-gaap_NetIncomeLoss	18,759us-gaap_NetIncomeLoss	16,437us-gaap_NetIncomeLoss	14,118us-gaap_NetIncomeLoss	12,680us-gaap_NetIncomeLoss	69,641us-gaap_NetIncomeLoss	61,994us-gaap_NetIncomeLoss	54,484us-gaap_NetIncomeLoss
Netsoft
Business Acquisition [Line Items]
Revenues									5,068
Net income									806
Acquisition related costs									75
Stock-based compensation expense									252
Jointech
Business Acquisition [Line Items]
Revenues									13,060
Net income									(3,090)
Acquisition related costs									361
Stock-based compensation expense									1,738
GGA
Business Acquisition [Line Items]
Revenues									19,809
Net income									822
Acquisition related costs									325
Stock-based compensation expense									4,322
Great Fridays
Business Acquisition [Line Items]
Revenues									1,821
Net income									(72)
Acquisition related costs									24
Stock-based compensation expense									239
Total
Business Acquisition [Line Items]
Revenues									39,758	46,500
Net income									(1,534)
Acquisition related costs									$ 785