PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
RIGP
Pension and other postretirement benefits
Consecutive service period before retirement used in calculation of employee's highest compensation	5 years
Service period before retirement considered for calculation of employee's highest compensation	10 years
Change in benefit obligation:
Benefit obligation at beginning of year	$ 22,657	$ 21,291
Service cost	217	244	284
Interest cost	538	827	827
Actuarial (gain) loss	(3,852)	2,233
Settlements	(2,300)	(1,853)
Benefit payments	(80)	(85)
Benefit obligation at end of year	17,180	22,657	21,291
Change in plan assets:
Fair value of plan assets at beginning of year	7,897	6,618
Actual return on plan assets	(161)	488
Employer contributions	647	2,729
Settlements	(2,300)	(1,853)
Benefit payments	(80)	(85)
Fair value of plan assets at end of year	6,003	7,897	6,618
Funded status at end of year	(11,177)	(14,760)
Retiree Medical Plan
Change in benefit obligation:
Benefit obligation at beginning of year	41,748	38,997
Service cost	431	315	303
Interest cost	1,409	1,794	1,927
Plan participants' contributions	624	567
Actuarial (gain) loss	(7,756)	2,410
Benefit payments	(1,307)	(2,335)
Benefit obligation at end of year	35,149	41,748	38,997
Change in plan assets:
Plan participants' contributions	624	567
Employer contributions	683	1,768
Benefit payments	(1,307)	(2,335)
Funded status at end of year	$ (35,149)	$ (41,748)