FAIR VALUE MEASUREMENTS AND FINANCIAL INSTRUMENTS (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) arrangement	Dec. 31, 2014 USD ($)
Auction Rate Securities
Cost basis	$ 27,765
Gross unrealized gain	$ 2,963	$ 1,387
Contingent Consideration Arrangments
Number of contingent consideration arrangements related to business acquisitions | arrangement	9
Number of contingent consideration arrangements with payment limit | arrangement	8
Current portion of contingent consideration	$ 2,600
Noncurrent portion of contingent consideration	31,200
Contingent Consideration Arrangements
Contingent Consideration Arrangments
Maximum amount of contingent consideration	240,700
Fair value of contingent consideration	33,400
Fair value of one contingent consideration arrangements without a maximum limit	$ 400
Contingent Consideration Arrangements | Minimum
Contingent Consideration Arrangments
Discount rate	12.00%
Contingent Consideration Arrangements | Maximum
Contingent Consideration Arrangments
Discount rate	25.00%
Auction Rate Security
Auction Rate Securities
Cost basis	$ 10,000	10,000
Gross unrealized gain	$ 5,900	$ 3,900