EMPLOYEE BENEFIT PLAN - Net periodic benefit cost and related components (Details) (Multiple Employer Retirement Income Plan, USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Multiple Employer Retirement Income Plan
Multiemployer Plans [Line Item]
Service cost
Interest cost	435	467
Expected return on plan assets	(510)	(462)
Amortization of net losses	196	167
Net periodic benefit cost	$ 121	$ 172