PARTNERS' CAPITAL - Change (Details) - USD ($) $ in Thousands	3 Months Ended		23 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020
Increase (Decrease) in Partners's Capital
Balance at beginning of period	$ 1,265,424	$ 1,187,687
Balance at beginning of period (in units)	126,915,597
Comprehensive income:
Net income	$ (144,707)	283,604
Actuarially determined long-term liability adjustments	938	(3,584)
COMPREHENSIVE (LOSS) INCOME	(143,769)	280,020
Settlement of deferred compensation plans	(1,310)	(7,817)
Purchase of units under unit repurchase program		(5,251)	$ (93,500)
Common unit-based compensation	(527)	2,743
Distributions on deferred common unit-based compensation	(986)	(1,280)
Distributions from consolidated company to affiliate noncontrolling interest	(288)	(262)
Distributions to Partners	(50,767)	(67,731)
Other	(273)
Balance at end of period	$ 1,067,504	1,388,109	$ 1,067,504
Balance at end of period (in units)	127,195,219		127,195,219
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partners's Capital
Balance at beginning of period	$ (77,993)	(46,871)
Comprehensive income:
Actuarially determined long-term liability adjustments	938	(3,584)
Balance at end of period	(77,055)	(50,455)	$ (77,055)
Noncontrolling Interest
Increase (Decrease) in Partners's Capital
Balance at beginning of period	11,935	5,290
Comprehensive income:
Net income	76	7,176
Distributions from consolidated company to affiliate noncontrolling interest	(288)	(262)
Balance at end of period	11,723	12,204	11,723
Limited Partners' Capital
Increase (Decrease) in Partners's Capital
Balance at beginning of period	$ 1,331,482	$ 1,229,268
Balance at beginning of period (in units)	126,915,597	128,095,511
Comprehensive income:
Net income	$ (144,783)	$ 276,428
Settlement of deferred compensation plans	$ (1,310)	$ (7,817)
Settlement of deferred compensation plans (in units)	279,622	596,650
Purchase of units under unit repurchase program		$ (5,251)
Purchase of units under unit repurchase program (in units)		(300,970)
Common unit-based compensation	$ (527)	$ 2,743
Distributions on deferred common unit-based compensation	(986)	(1,280)
Distributions to Partners	(50,767)	(67,731)
Other	(273)
Balance at end of period	$ 1,132,836	$ 1,426,360	$ 1,132,836
Balance at end of period (in units)	127,195,219	128,391,191	127,195,219