MULTIEMPLOYER DEFINED BENEFIT PENSION PLANS (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 agreement plan	Dec. 31, 2010	Dec. 31, 2009
MULTIEMPLOYER DEFINED BENEFIT PENSION PLANS
Number of multiemployer defined benefit pensions plans	3
Number of significant collective-bargaining agreements	4
Contributions by employer	$ 1,500	$ 1,300	$ 800
Red Zone
MULTIEMPLOYER DEFINED BENEFIT PENSION PLANS
Contributions by employer	1,454	1,236	773
Red Zone | Maximum
MULTIEMPLOYER DEFINED BENEFIT PENSION PLANS
Percentage of plan funded	65.00%
Yellow Zone | Maximum
MULTIEMPLOYER DEFINED BENEFIT PENSION PLANS
Percentage of plan funded	80.00%
Green Zone | Minimum
MULTIEMPLOYER DEFINED BENEFIT PENSION PLANS
Percentage of plan funded	80.00%
Southeast and Southwest Areas Pension Fund | Red Zone
MULTIEMPLOYER DEFINED BENEFIT PENSION PLANS
Contributions by employer	859	782	711
Employees Local 169 & Employers Joint Pension Fund | Red Zone
MULTIEMPLOYER DEFINED BENEFIT PENSION PLANS
Contributions by employer	76	66	62
GCIU - Employer Retirement Fund
MULTIEMPLOYER DEFINED BENEFIT PENSION PLANS
Number of significant collective-bargaining agreements	2
GCIU - Employer Retirement Fund | Red Zone
MULTIEMPLOYER DEFINED BENEFIT PENSION PLANS
Contributions by employer	$ 519	$ 478