INCENTIVE COMPENSATION (Details) (USD $)	3 Months Ended						3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Vested units	Mar. 31, 2014 Incentive Plan	Mar. 31, 2013 Incentive Plan	Dec. 31, 2013 Incentive Plan Vested units	Mar. 31, 2014 Matching contributions expensed for employee savings plan	Mar. 31, 2013 Matching contributions expensed for employee savings plan
Unit based compensation
Matching contributions expensed for employee savings plan							$ 356,000	$ 149,000
Employer matching contribution, percent of employee's contribution							100.00%
Vesting period				3 years
Units
Unvested - December 31, 2013						182,673
Granted units				2,000
Units recaptured for tax withholdings			(134)
Unvested at the end of the period (in shares)				184,473		182,673
Weighted-average grant date fair value
Unvested - December 31, 2013						$ 22.55
Granted units				$ 18.04
Vested units			$ 24.41
Unvested - March 31, 2014				$ 22.51		$ 22.55
Fair value				36,000	15,000
Share-based compensation cost not yet recognized				3,200,000	2,900,000
Period of amortization of compensation expense				3 years
Units available for issuance (in shares)				1,525,121	1,609,900
Unit-based compensation	529,000	408,000
Units recaptured for tax withholdings				(66)
Units recaptured for tax withholdings				$ 24.41
Employer matching contribution, percent of employees' gross pay							6.00%
Maximum annual contributions by employer, amount (per employee)							$ 17,500