COMMITMENTS, CONTINGENCIES AND LITIGATION -Credit Agreement (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Aug. 31, 2012	Dec. 31, 2011
Line of Credit Facility [Line Items]
Credit limit		$ 70,000
Letters of credit issued	13,578		11,130
Borrowing capacity	25,921		48,770
Revolving credit facility
Line of Credit Facility [Line Items]
Credit limit	70,000		60,000
Outstanding principal balance	30,501		100
Interest rate	3.70%		5.00%
Term Loan
Line of Credit Facility [Line Items]
Credit limit	67,300		59,000
Outstanding principal balance	$ 64,873		$ 58,177
Interest rate	3.70%		3.80%