Consolidated Statement of Changes in Capital (unaudited) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Increase (Decrease) in Partners' Capital [Roll Forward]
Balance at beginning of year (in shares)		25,023,128			25,023,128
Balance at beginning of year	$ 429,519	$ 476,419	$ 503,394	$ 492,508	$ 476,419	$ 492,508
Net income (loss)	(1,677)	(61,607)	21,034	15,622	$ (63,284)	36,656
Currency translation adjustments	1,373	(2,936)	(1,797)	1,303
Equity compensation - restricted units	49	104	227	164
Deconsolidation of API (see Note 3)		17,481
Other, net	$ 25	58	(22)
Unrealized gains on derivative financial instruments			(425)	518
Purchases of SPLP common units				(6,721)
Balance at end of period (in shares)	24,929,253				24,929,253
Balance at end of year	$ 429,289	429,519	522,411	503,394	$ 429,289	522,411
Total Partners' Capital
Increase (Decrease) in Partners' Capital [Roll Forward]
Balance at beginning of year	425,523	472,613	499,729	488,787	472,613	488,787
Net income (loss)	(1,868)	(61,737)	21,063	15,678
Currency translation adjustments	1,373	(2,936)	(1,797)	1,303
Equity compensation - restricted units	49	104	227	164
Deconsolidation of API (see Note 3)		17,481
Other, net	(3)	(2)	(22)
Unrealized gains on derivative financial instruments			(425)	518
Purchases of SPLP common units				(6,721)
Balance at end of year	$ 425,074	$ 425,523	$ 518,775	$ 499,729	$ 425,074	$ 518,775
Common Units
Increase (Decrease) in Partners' Capital [Roll Forward]
Balance at beginning of year (in shares)	37,661,138	37,670,992	37,606,531	37,436,531	37,670,992	37,436,531
Equity compensation - restricted units (in shares)	(84,021)	(9,854)	52,475	170,000
Balance at end of period (in shares)	37,577,117	37,661,138	37,659,006	37,606,531	37,577,117	37,659,006
Treasury Units
Increase (Decrease) in Partners' Capital [Roll Forward]
Balance at beginning of year (in shares)	12,647,864	12,647,864	12,647,864	12,142,528	12,647,864	12,142,528
Balance at beginning of year	$ (198,781)	$ (198,781)	$ (198,781)	$ (192,060)	$ (198,781)	$ (192,060)
Purchases of SPLP common units (in shares)				(505,336)
Purchases of SPLP common units				$ (6,721)
Balance at end of period (in shares)	12,647,864	12,647,864	12,647,864	12,647,864	12,647,864	12,647,864
Balance at end of year	$ (198,781)	$ (198,781)	$ (198,781)	$ (198,781)	$ (198,781)	$ (198,781)
Partners' Capital
Increase (Decrease) in Partners' Capital [Roll Forward]
Balance at beginning of year	602,400	664,035	675,152	666,031	664,035	666,031
Net income (loss)	(1,868)	(61,737)	21,063	15,678
Equity compensation - restricted units	49	104	227	164
Other, net	(3)	(2)	(22)
Purchases of SPLP common units				(6,721)
Balance at end of year	600,578	602,400	696,420	675,152	600,578	696,420
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partners' Capital [Roll Forward]
Balance at beginning of year	(176,877)	(191,422)	(175,423)	(177,244)	(191,422)	(177,244)
Currency translation adjustments	1,373	(2,936)	(1,797)	1,303
Deconsolidation of API (see Note 3)		17,481
Unrealized gains on derivative financial instruments			(425)	518
Balance at end of year	(175,504)	(176,877)	(177,645)	(175,423)	(175,504)	(177,645)
Noncontrolling Interests in Consolidated Entities
Increase (Decrease) in Partners' Capital [Roll Forward]
Balance at beginning of year	3,996	3,806	3,665	3,721	3,806	3,721
Net income (loss)	191	130	(29)	(56)
Other, net	28	60
Balance at end of year	$ 4,215	$ 3,996	$ 3,636	$ 3,665	$ 4,215	$ 3,636