REVOLVING CREDIT FACILITY (Details) (USD $)					12 Months Ended							12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2012 Revolving Credit Facility multiplier	Dec. 31, 2012 Revolving Credit Facility Minimum	Dec. 31, 2012 Revolving Credit Facility Maximum	Dec. 31, 2012 Revolving Credit Facility Prime rate	Dec. 31, 2011 Revolving Credit Facility Prime rate	Dec. 31, 2012 Revolving Credit Facility Prime rate Minimum	Dec. 31, 2012 Revolving Credit Facility Prime rate Maximum	Dec. 31, 2012 Revolving Credit Facility LIBOR	Dec. 31, 2011 Revolving Credit Facility LIBOR	Dec. 31, 2012 Revolving Credit Facility LIBOR Minimum	Dec. 31, 2012 Revolving Credit Facility LIBOR Maximum
Revolving credit facility
Revolving credit limit					$ 125,000,000
Potential future expansion of the Facility under accordion feature					175,000,000
Variable rate basis								Bank's prime rate plus a margin				LIBOR plus a margin
Interest rate margin per debt instrument (as a percent)										1.25%	2.25%			2.25%	3.25%
Actual interest rate margin (as a percent)								1.25%				2.25%
Weighted average interest rate (as a percent)								4.50%	4.50%			2.68%	2.59%
Quarterly commitment fee on the average daily unused facility balance (as a percent)						0.30%	0.50%
EBITDA multiplier					3.0
Percentage of acquired EBITDA which can be included in covenants calculation							50.00%
Irrevocable letters of credit outstanding					6,400,000
Borrowing capacity permitted to be used per formula					97,800,000
Remaining borrowing capacity available for use					91,400,000
Minimum net worth required to be maintained					156,500,000
Company's net worth	$ 204,315,000	$ 206,297,000	$ 182,168,000	$ 148,977,000