Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenue	$ 397,065	$ 594,235	$ 1,072,601	$ 1,575,342
Costs of products sold, exclusive of depreciation and amortization shown below	274,639	458,063	710,869	1,211,703
Operating	53,267	69,377	167,157	179,579
General and administrative	23,045	23,296	78,272	63,882
Depreciation and amortization	26,022	25,200	74,430	70,899
Loss (gain) on disposal of long-lived assets, net	(951)	1,376	1,479	20,633
Total expenses	376,022	577,312	1,032,207	1,546,696
Earnings from equity method investments	16,237	14,223	60,699	48,372
Gain on issuance of common units by equity method investee	136	18,772	6,033	26,899
Operating income	37,416	49,918	107,126	103,917
Other expenses (income), net	17,829	(6,368)	33,725	30,618
Income (loss) from continuing operations before income taxes	19,587	56,286	73,401	73,299
Total assets at September 30, 2015 (excluding intersegment receivables)	2,877,568		2,877,568		$ 2,589,802
Crude [Member]
Segment Reporting Information [Line Items]
Revenue	241,086	376,856	606,057	961,526
Costs of products sold, exclusive of depreciation and amortization shown below	195,244	333,646	473,522	843,928
Operating	19,329	22,057	64,446	54,885
General and administrative	7,733	4,696	19,687	15,076
Depreciation and amortization	10,634	8,395	31,385	27,153
Loss (gain) on disposal of long-lived assets, net	(603)	291	(530)	230
Total expenses	232,337	369,085	588,510	941,272
Earnings from equity method investments	17,115	18,705	55,662	44,295
Gain on issuance of common units by equity method investee	0	0	0
Operating income	25,864	26,476	73,209	64,549
Other expenses (income), net	16,030	10,526	39,759	20,367
Income (loss) from continuing operations before income taxes	9,834	15,950	33,450	44,182
Total assets at September 30, 2015 (excluding intersegment receivables)	1,377,143		1,377,143
SemStream [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Costs of products sold, exclusive of depreciation and amortization shown below	0	0	0	0
Operating	0	0	0	0
General and administrative	7	30	22	91
Depreciation and amortization	0	0	0	0
Loss (gain) on disposal of long-lived assets, net	0	0	0	0
Total expenses	7	30	22	91
Earnings from equity method investments	(878)	(4,482)	5,037	4,077
Gain on issuance of common units by equity method investee	136	18,772	6,033	26,899
Operating income	(749)	14,260	11,048	30,885
Other expenses (income), net	(1,352)	(28,041)	(18,527)	(30,582)
Income (loss) from continuing operations before income taxes	603	42,301	29,575	61,467
Total assets at September 30, 2015 (excluding intersegment receivables)	117,280		117,280
SemCAMS [Member]
Segment Reporting Information [Line Items]
Revenue	33,152	53,800	98,791	133,037
Costs of products sold, exclusive of depreciation and amortization shown below	27	97	235	235
Operating	21,062	33,537	63,058	86,039
General and administrative	3,600	3,836	11,169	11,390
Depreciation and amortization	3,198	5,113	9,451	11,021
Loss (gain) on disposal of long-lived assets, net	(917)	(35)	(917)	(950)
Total expenses	26,970	42,548	82,996	107,735
Earnings from equity method investments	0	0	0	0
Gain on issuance of common units by equity method investee	0	0	0	0
Operating income	6,182	11,252	15,795	25,302
Other expenses (income), net	1,702	3,920	8,034	11,825
Income (loss) from continuing operations before income taxes	4,480	7,332	7,761	13,477
Total assets at September 30, 2015 (excluding intersegment receivables)	586,944		586,944
SemGas [Member]
Segment Reporting Information [Line Items]
Revenue	65,070	96,829	198,048	290,361
Costs of products sold, exclusive of depreciation and amortization shown below	36,915	68,722	114,344	215,535
Operating	8,475	8,965	25,320	24,421
General and administrative	2,376	2,312	7,080	6,524
Depreciation and amortization	8,601	7,064	23,098	19,312
Loss (gain) on disposal of long-lived assets, net	445	(12)	1,894	20,092
Total expenses	56,812	87,051	171,736	285,884
Earnings from equity method investments	0	0	0	0
Gain on issuance of common units by equity method investee	0	0	0	0
Operating income	8,258	9,778	26,312	4,477
Other expenses (income), net	3,504	2,330	9,624	6,032
Income (loss) from continuing operations before income taxes	4,754	7,448	16,688	(1,555)
Total assets at September 30, 2015 (excluding intersegment receivables)	722,615		722,615
SemLogistics [Member]
Segment Reporting Information [Line Items]
Revenue	5,659	1,299	17,090	10,070
Costs of products sold, exclusive of depreciation and amortization shown below	0		0	615
Operating	1,955	2,148	6,610	6,168
General and administrative	1,757	1,595	5,680	4,546
Depreciation and amortization	2,173	2,543	6,367	7,593
Loss (gain) on disposal of long-lived assets, net	0	1,139	0	(2,495)
Total expenses	5,885	7,425	18,657	16,427
Earnings from equity method investments	0	0	0	0
Gain on issuance of common units by equity method investee	0	0	0	0
Operating income	(226)	(6,126)	(1,567)	(6,357)
Other expenses (income), net	1,021	969	1,705	1,303
Income (loss) from continuing operations before income taxes	(1,247)	(7,095)	(3,272)	(7,660)
Total assets at September 30, 2015 (excluding intersegment receivables)	157,087		157,087
SemMexico [Member]
Segment Reporting Information [Line Items]
Revenue	56,260	75,177	169,209	209,758
Costs of products sold, exclusive of depreciation and amortization shown below	46,615	65,324	139,362	180,800
Operating	2,447	2,670	7,724	8,066
General and administrative	2,823	2,928	7,588	8,791
Depreciation and amortization	993	1,655	3,083	4,538
Loss (gain) on disposal of long-lived assets, net	124	(7)	105	(35)
Total expenses	53,002	72,570	157,862	202,160
Earnings from equity method investments	0	0	0	0
Gain on issuance of common units by equity method investee	0	0	0	0
Operating income	3,258	2,607	11,347	7,598
Other expenses (income), net	143	31	268	(70)
Income (loss) from continuing operations before income taxes	3,115	2,576	11,079	7,668
Total assets at September 30, 2015 (excluding intersegment receivables)	98,029		98,029
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue	(4,162)	(9,726)	(16,594)	(29,410)
Costs of products sold, exclusive of depreciation and amortization shown below	(4,162)	(9,726)	(16,594)	(29,410)
Operating	(1)	0	(1)	0
General and administrative	4,749	7,899	27,046	17,464
Depreciation and amortization	423	430	1,046	1,282
Loss (gain) on disposal of long-lived assets, net	0	0	927	3,791
Total expenses	1,009	(1,397)	12,424	(6,873)
Earnings from equity method investments	0	0	0	0
Gain on issuance of common units by equity method investee	0	0	0	0
Operating income	(5,171)	(8,329)	(29,018)	(22,537)
Other expenses (income), net	(3,219)	3,897	(7,138)	21,743
Income (loss) from continuing operations before income taxes	(1,952)	(12,226)	(21,880)	(44,280)
Total assets at September 30, 2015 (excluding intersegment receivables)	(181,530)		(181,530)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	397,065	594,235	1,072,601	1,575,342
Operating Segments [Member] | Crude [Member]
Segment Reporting Information [Line Items]
Revenue	241,086	376,856	606,057	961,526
Operating Segments [Member] | SemStream [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Operating Segments [Member] | SemCAMS [Member]
Segment Reporting Information [Line Items]
Revenue	33,152	53,800	98,791	133,037
Operating Segments [Member] | SemGas [Member]
Segment Reporting Information [Line Items]
Revenue	60,908	87,103	181,454	260,951
Operating Segments [Member] | SemLogistics [Member]
Segment Reporting Information [Line Items]
Revenue	5,659	1,299	17,090	10,070
Operating Segments [Member] | SemMexico [Member]
Segment Reporting Information [Line Items]
Revenue	56,260	75,177	169,209	209,758
Operating Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intersegment Eliminations [Member] | Crude [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intersegment Eliminations [Member] | SemStream [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intersegment Eliminations [Member] | SemCAMS [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intersegment Eliminations [Member] | SemGas [Member]
Segment Reporting Information [Line Items]
Revenue	4,162	9,726	16,594	29,410
Intersegment Eliminations [Member] | SemLogistics [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intersegment Eliminations [Member] | SemMexico [Member]
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intersegment Eliminations [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue	$ (4,162)	$ (9,726)	$ (16,594)	$ (29,410)