PARTNERS' CAPITAL - Change (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	29 Months Ended
Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020
Increase (Decrease) in Partners's Capital
Balance at beginning of period	$ 1,023,152	$ 1,067,504	$ 1,265,424	$ 1,379,479	$ 1,388,109	$ 1,187,687	$ 1,265,424	$ 1,187,687
Balance at beginning of period (in units)			126,915,597				126,915,597
Comprehensive income (loss):
Net income (loss)	27,235	(46,679)	$ (144,707)	39,201	58,184	283,604	$ (164,151)	380,989
Actuarially determined long-term liability adjustments	844	939	938	(119)	(118)	(3,584)	2,721	(3,821)
COMPREHENSIVE INCOME (LOSS)	28,079	(45,740)	(143,769)	39,082	58,066	280,020	(161,430)	377,168
Settlement of deferred compensation plans			(1,310)			(7,817)
Purchase of units under unit repurchase program						(5,251)			$ (93,500)
Common unit-based compensation	1,645	1,610	(527)	3,066	3,021	2,743
Distributions on deferred common unit-based compensation			(986)	(822)	(799)	(1,280)
Distributions from consolidated company to noncontrolling interest	(93)	(222)	(288)	(183)	(228)	(262)
Distributions to Partners			(50,767)	(69,331)	(68,690)	(67,731)
Other			(273)
Balance at end of period	$ 1,052,783	1,023,152	1,067,504	1,351,291	1,379,479	1,388,109	$ 1,052,783	1,351,291	$ 1,052,783
Balance at end of period (in units)	127,195,219						127,195,219		127,195,219
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partners's Capital
Balance at beginning of period	$ (76,116)	(77,055)	(77,993)	(50,573)	(50,455)	(46,871)	$ (77,993)	(46,871)
Comprehensive income (loss):
Actuarially determined long-term liability adjustments	844	939	938	(119)	(118)	(3,584)
Balance at end of period	(75,272)	(76,116)	(77,055)	(50,692)	(50,573)	(50,455)	(75,272)	(50,692)	$ (75,272)
Noncontrolling Interest
Increase (Decrease) in Partners's Capital
Balance at beginning of period	11,486	11,723	11,935	12,090	12,204	5,290	11,935	5,290
Comprehensive income (loss):
Net income (loss)	36	(15)	76	117	114	7,176
Distributions from consolidated company to noncontrolling interest	(93)	(222)	(288)	(183)	(228)	(262)
Balance at end of period	11,429	11,486	11,723	12,024	12,090	12,204	11,429	12,024	11,429
Limited Partners' Capital
Increase (Decrease) in Partners's Capital
Balance at beginning of period	$ 1,087,782	$ 1,132,836	$ 1,331,482	$ 1,417,962	$ 1,426,360	$ 1,229,268	$ 1,331,482	$ 1,229,268
Balance at beginning of period (in units)	127,195,219	127,195,219	126,915,597	128,391,191	128,391,191	128,095,511	126,915,597	128,095,511
Comprehensive income (loss):
Net income (loss)	$ 27,199	$ (46,664)	$ (144,783)	$ 39,084	$ 58,070	$ 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	1,645	1,610	$ (527)	3,066	3,021	$ 2,743
Distributions on deferred common unit-based compensation			(986)	(822)	(799)	(1,280)
Distributions to Partners			(50,767)	(69,331)	(68,690)	(67,731)
Other			(273)
Balance at end of period	$ 1,116,626	$ 1,087,782	$ 1,132,836	$ 1,389,959	$ 1,417,962	$ 1,426,360	$ 1,116,626	$ 1,389,959	$ 1,116,626
Balance at end of period (in units)	127,195,219	127,195,219	127,195,219	128,391,191	128,391,191	128,391,191	127,195,219	128,391,191	127,195,219

Change in the number of shares in each class of partners' capital accounts during the year due to the vesting or issuance of shares under deferred compensation and long-term incentive plans. All partners include general, limited and preferred partners.

No definition available.