DERIVATIVE FINANCIAL INSTRUMENTS (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 04, 2012
Derivatives
Fair Value, Current portion of long-term liabilities	$ (720,000)	$ (3,164,000)
Percentage of debt hedged	41.00%	69.00%
Number of U.S. and European banks which are counterparties	4
Number of swap agreements that provide for the entity or the counterparties to post collateral	0
Cash flow hedges
Derivatives
Total Fair Value	(4,311,000)	(7,083,000)
Cash flow hedges | Fixed to 1-month floating LIBOR, one
Derivatives
Reference rate for receiving interest	1-month floating LIBOR	1-month floating LIBOR
Notional amount	275,000,000	200,000,000
Fair Value, Other long-term liabilities	(3,591,000)	(2,758,000)
Cash flow hedges | Fixed to 1-month floating LIBOR, two
Derivatives
Reference rate for receiving interest	1-month floating LIBOR	1-month floating LIBOR
Notional amount	100,000,000	100,000,000
Fair Value, Current portion of long-term liabilities	(720,000)	(1,069,000)
Cash flow hedges | Forward starting fixed to 1-month floating LIBOR
Derivatives
Reference rate for receiving interest	1-month floating LIBOR	1-month floating LIBOR
Notional amount		75,000,000
Fair Value, Other long-term liabilities		(1,161,000)
De-designated Hedges | Fixed to 3-month floating LIBOR, one
Derivatives
Reference rate for receiving interest	3-month floating LIBOR	3-month floating LIBOR
Notional amount		130,000,000
Fair Value, Current portion of long-term liabilities		(1,300,000)
De-designated Hedges | 3-month floating LIBOR minus spread to 1-month floating LIBOR, one
Derivatives
Reference rate for receiving interest	1-month floating LIBOR	1-month floating LIBOR
Reference rate for paying interest	3-month floating LIBOR minus spread	3-month floating LIBOR minus spread
Notional amount		130,000,000
Fair Value, Current portion of long-term liabilities		(16,000)
De-designated Hedges | Fixed to 1-month floating LIBOR, one
Derivatives
Reference rate for receiving interest	1-month floating LIBOR	1-month floating LIBOR
Notional amount		200,000,000
Fair Value, Current portion of long-term liabilities		(779,000)
De-designated Hedges | Interest rate swaps
Derivatives
Notional amount			660,000,000
Notional amount of derivatives expired		200,000,000
Gain recognized as a reduction to interest expense	$ 2,100,000