Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information
Revenue	$ 457,328	$ 357,748	$ 324,244	$ 287,696	$ 315,837	$ 277,852	$ 331,777	$ 312,031	$ 1,427,016	$ 1,237,497	$ 1,465,246
Costs of products sold, exclusive of depreciation and amortization shown below									1,020,100	874,885	1,144,439
Operating									223,585	224,700	155,041
General and administrative									78,597	71,918	75,447
Depreciation and amortization									66,409	48,210	49,823
Gain (Loss) on Sale of Assets and Asset Impairment Charges											(301)
Loss (gain) on disposal or impairment of long-lived assets, net	(109)	408	(376)	(162)	(35)	(3,615)	119	0	(239)	(3,531)	301
Total expenses	448,687	345,387	311,727	282,651	306,885	267,343	330,887	311,067	1,388,452	1,216,182	1,425,051
Earnings from equity method investments	12,788	7,483	14,861	17,345	13,133	3,116	12,289	7,498	52,477	36,036	15,004
Gain on issuance of common units by equity method investee	26,873	0	0	0					26,873	0	0
Operating income (loss)	48,302	19,844	27,378	22,390	22,085	13,625	13,179	8,462	117,914	57,351	55,199
Interest expense (income)									25,142	8,902	60,138
Other expense (income), net									44,273	21,569	(14,989)
Total other expenses, net	17,646	13,294	10,613	27,862	5,567	11,701	5,587	7,616	69,415	30,471	45,149
Income (loss) from continuing operations before income taxes	30,656	6,550	16,765	(5,472)	16,518	1,924	7,592	846	48,499	26,880	10,050
Additions to long-lived assets									229,318	121,255	66,480
Total assets	2,470,614				1,748,179				2,470,614	1,748,179
Equity method investments	565,124				387,802				565,124	387,802
SemStream [Member]
Segment Reporting Information
Revenue									0	7	608,334
Costs of products sold, exclusive of depreciation and amortization shown below									0	33	595,434
Operating									1	(37)	6,448
General and administrative									600	930	7,336
Depreciation and amortization									0	0	3,501
Gain (Loss) on Sale of Assets and Asset Impairment Charges											45,821
Loss (gain) on disposal or impairment of long-lived assets, net									6	214
Total expenses									607	1,140	566,898
Earnings from equity method investments									7,123	(403)	0
Gain on issuance of common units by equity method investee									26,873
Operating income (loss)									33,389	(1,536)	41,436
Interest expense (income)									(4,810)	(3,449)	17,152
Other expense (income), net									128	(21)	(2,112)
Total other expenses, net									(4,682)	(3,470)	15,040
Income (loss) from continuing operations before income taxes									38,071	1,934	26,396
Additions to long-lived assets									0	0	2,197
Total assets	208,847				175,028				208,847	175,028
Equity method investments	208,848				174,398				208,848	174,398
SemCAMS [Member]
Segment Reporting Information
Revenue									198,450	223,219	163,367
Costs of products sold, exclusive of depreciation and amortization shown below									305	768	218
Operating									150,319	174,284	110,814
General and administrative									14,940	14,020	16,816
Depreciation and amortization									10,766	10,589	10,233
Gain (Loss) on Sale of Assets and Asset Impairment Charges											8
Loss (gain) on disposal or impairment of long-lived assets, net									0	0
Total expenses									176,330	199,661	138,073
Earnings from equity method investments									0	0	0
Gain on issuance of common units by equity method investee									0
Operating income (loss)									22,120	23,558	25,294
Interest expense (income)									18,928	18,727	24,685
Other expense (income), net									(20)	14	(2,811)
Total other expenses, net									18,908	18,741	21,874
Income (loss) from continuing operations before income taxes									3,212	4,817	3,420
Additions to long-lived assets									56,122	13,340	4,874
Total assets	306,001				302,143				306,001	302,143
Equity method investments	0				0				0	0
SemGas [Member]
Segment Reporting Information
Revenue									231,119	127,870	105,248
Costs of products sold, exclusive of depreciation and amortization shown below									169,800	100,677	75,066
Operating									20,200	12,712	9,027
General and administrative									7,971	6,195	6,521
Depreciation and amortization									14,517	7,043	5,986
Gain (Loss) on Sale of Assets and Asset Impairment Charges											(4)
Loss (gain) on disposal or impairment of long-lived assets, net									665	46
Total expenses									213,153	126,673	96,604
Earnings from equity method investments									0	0	0
Gain on issuance of common units by equity method investee									0
Operating income (loss)									17,966	1,197	8,644
Interest expense (income)									3,268	1,461	2,346
Other expense (income), net									(3)	0	(10)
Total other expenses, net									3,265	1,461	2,336
Income (loss) from continuing operations before income taxes									14,701	(264)	6,308
Additions to long-lived assets									97,021	47,140	14,952
Total assets	552,095				133,864				552,095	133,864
Equity method investments	0				0				0	0
SemLogistics [Member]
Segment Reporting Information
Revenue									11,671	12,341	23,314
Costs of products sold, exclusive of depreciation and amortization shown below									380	196	152
Operating									7,444	5,921	6,206
General and administrative									5,854	5,652	6,712
Depreciation and amortization									9,426	9,780	9,271
Gain (Loss) on Sale of Assets and Asset Impairment Charges											(44,663)
Loss (gain) on disposal or impairment of long-lived assets, net									0	0
Total expenses									23,104	21,549	67,004
Earnings from equity method investments									0	0	0
Gain on issuance of common units by equity method investee									0
Operating income (loss)									(11,433)	(9,208)	(43,690)
Interest expense (income)									1,435	2,486	1,005
Other expense (income), net									(400)	(420)	46
Total other expenses, net									1,035	2,066	1,051
Income (loss) from continuing operations before income taxes									(12,468)	(11,274)	(44,741)
Additions to long-lived assets									2,071	1,188	5,313
Total assets	168,835				174,218				168,835	174,218
Equity method investments	0				0				0	0
SemMexico [Member]
Segment Reporting Information
Revenue									242,559	263,870	218,187
Costs of products sold, exclusive of depreciation and amortization shown below									209,841	236,851	192,068
Operating									9,379	7,677	5,006
General and administrative									10,700	9,433	11,560
Depreciation and amortization									5,991	6,171	6,502
Gain (Loss) on Sale of Assets and Asset Impairment Charges											200
Loss (gain) on disposal or impairment of long-lived assets, net									(854)	(290)
Total expenses									235,057	259,842	214,936
Earnings from equity method investments									0	0	0
Gain on issuance of common units by equity method investee									0
Operating income (loss)									7,502	4,028	3,251
Interest expense (income)									188	314	365
Other expense (income), net									(652)	(38)	(173)
Total other expenses, net									(464)	276	192
Income (loss) from continuing operations before income taxes									7,966	3,752	3,059
Additions to long-lived assets									6,375	3,396	4,667
Total assets	104,154				94,594				104,154	94,594
Equity method investments	0				0				0	0
Corporate and other [Member]
Segment Reporting Information
Revenue									(23,985)	(10,607)	(84,525)
Costs of products sold, exclusive of depreciation and amortization shown below									(23,985)	(10,606)	(84,764)
Operating									0	0	70
General and administrative									21,766	22,367	16,745
Depreciation and amortization									2,001	2,496	2,951
Gain (Loss) on Sale of Assets and Asset Impairment Charges											(1,599)
Loss (gain) on disposal or impairment of long-lived assets, net									0	0
Total expenses									(218)	14,257	(63,399)
Earnings from equity method investments									0	0	0
Gain on issuance of common units by equity method investee									0
Operating income (loss)									(23,767)	(24,864)	(21,126)
Interest expense (income)									(8,790)	(10,228)	10,836
Other expense (income), net									45,234	22,003	(8,329)
Total other expenses, net									36,444	11,775	2,507
Income (loss) from continuing operations before income taxes									(60,211)	(36,639)	(23,633)
Additions to long-lived assets									734	14,827	2,080
Total assets	60,198				97,192				60,198	97,192
Equity method investments	0				0				0	0
Crude [Member]
Segment Reporting Information
Revenue									767,202	620,797	431,321
Costs of products sold, exclusive of depreciation and amortization shown below									663,759	546,966	366,265
Operating									36,242	24,143	17,470
General and administrative									16,766	13,321	9,757
Depreciation and amortization									23,708	12,131	11,379
Gain (Loss) on Sale of Assets and Asset Impairment Charges											(64)
Loss (gain) on disposal or impairment of long-lived assets, net									(56)	(3,501)
Total expenses									740,419	593,060	404,935
Earnings from equity method investments									45,354	36,439	15,004
Gain on issuance of common units by equity method investee									0
Operating income (loss)									72,137	64,176	41,390
Interest expense (income)									14,923	(409)	3,749
Other expense (income), net									(14)	31	(1,600)
Total other expenses, net									14,909	(378)	2,149
Income (loss) from continuing operations before income taxes									57,228	64,554	39,241
Additions to long-lived assets									66,995	41,364	32,397
Total assets	1,070,484				771,140				1,070,484	771,140
Equity method investments	356,276				213,404				356,276	213,404
Intersegment Eliminations [Member]
Segment Reporting Information
Revenue									0	0	0
Intersegment Eliminations [Member] | SemStream [Member]
Segment Reporting Information
Revenue									0	0	46,738
Intersegment Eliminations [Member] | SemCAMS [Member]
Segment Reporting Information
Revenue									0	0	0
Intersegment Eliminations [Member] | SemGas [Member]
Segment Reporting Information
Revenue									23,985	10,606	38,588
Intersegment Eliminations [Member] | SemLogistics [Member]
Segment Reporting Information
Revenue									0	0	0
Intersegment Eliminations [Member] | SemMexico [Member]
Segment Reporting Information
Revenue									0	0	0
Intersegment Eliminations [Member] | Corporate and other [Member]
Segment Reporting Information
Revenue									(23,985)	(10,606)	(85,326)
Intersegment Eliminations [Member] | Crude [Member]
Segment Reporting Information
Revenue									0	0	0
Operating Segments [Member]
Segment Reporting Information
Revenue									1,427,016	1,237,497	1,465,246
Operating Segments [Member] | SemStream [Member]
Segment Reporting Information
Revenue									0	7	561,596
Operating Segments [Member] | SemCAMS [Member]
Segment Reporting Information
Revenue									198,450	223,219	163,367
Operating Segments [Member] | SemGas [Member]
Segment Reporting Information
Revenue									207,134	117,264	66,660
Operating Segments [Member] | SemLogistics [Member]
Segment Reporting Information
Revenue									11,671	12,341	23,314
Operating Segments [Member] | SemMexico [Member]
Segment Reporting Information
Revenue									242,559	263,870	218,187
Operating Segments [Member] | Corporate and other [Member]
Segment Reporting Information
Revenue									0	(1)	801
Operating Segments [Member] | Crude [Member]
Segment Reporting Information
Revenue									$ 767,202	$ 620,797	$ 431,321