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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Multiple Employer Retirement Income Plan
Multiemployer Plans [Line Item]
Service cost
Interest cost	436	468	1,306	1,402
Expected return on plan assets	(511)	(462)	(1,533)	(1,386)
Amortization of net losses	197	167	588	501
Net periodic benefit cost	$ 122	$ 173	$ 361	$ 517