Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Segment Reporting Information
Revenue	$ 357,748	$ 277,852	$ 969,688	$ 921,660
Costs of products sold, exclusive of depreciation and amortization shown below	255,554	189,830	680,632	651,283
Operating	52,360	52,367	162,813	172,750
General and administrative	20,952	16,680	54,887	53,073
Depreciation and amortization	16,113	12,081	41,563	35,687
Loss (gain) on disposal of long-lived assets, net	408	(3,615)	(130)	(3,496)
Total expenses	345,387	267,343	939,765	909,297
Earnings from equity method investments	7,483	3,116	39,689	22,903
Operating income	19,844	13,625	69,612	35,266
Other expenses (income), net	13,294	11,701	51,769	24,904
Income (loss) from continuing operations before income taxes	6,550	1,924	17,843	10,362
Total assets (excluding intersegment receivables)	2,390,402		2,390,402		1,748,179
Crude [Member]
Segment Reporting Information
Revenue	181,831	131,616	514,485	468,748
Costs of products sold, exclusive of depreciation and amortization shown below	157,550	111,790	446,507	412,847
Operating	9,098	6,042	20,527	17,957
General and administrative	3,360	5,015	10,778	9,796
Depreciation and amortization	4,130	3,066	11,327	9,032
Loss (gain) on disposal of long-lived assets, net	0	(3,500)	(25)	(3,444)
Total expenses	174,138	122,413	489,114	446,188
Earnings from equity method investments	10,771	10,021	31,861	25,053
Operating income	18,464	19,224	57,232	47,613
Other expenses (income), net	3,634	(119)	10,925	(739)
Income (loss) from continuing operations before income taxes	14,830	19,343	46,307	48,352
Total assets (excluding intersegment receivables)	1,012,535		1,012,535
SemStream [Member]
Segment Reporting Information
Revenue	0	0		7
Costs of products sold, exclusive of depreciation and amortization shown below	0	0	0	33
Operating	0	7	1	(18)
General and administrative	114	528	430	582
Depreciation and amortization	0	0	0	0
Loss (gain) on disposal of long-lived assets, net	0	0	6	0
Total expenses	114	535	437	597
Earnings from equity method investments	(3,288)	(6,905)	7,828	(2,150)
Operating income	(3,402)	(7,440)	7,391	(2,740)
Other expenses (income), net	(1,238)	(2,551)	(3,399)	(2,507)
Income (loss) from continuing operations before income taxes	(2,164)	(4,889)	10,790	(233)
Total assets (excluding intersegment receivables)	187,632		187,632
SemCAMS [Member]
Segment Reporting Information
Revenue	48,979	54,301	151,219	169,149
Costs of products sold, exclusive of depreciation and amortization shown below	106	309	290	499
Operating	33,980	40,081	116,372	135,165
General and administrative	3,446	3,354	10,933	10,404
Depreciation and amortization	2,631	2,664	7,925	7,910
Loss (gain) on disposal of long-lived assets, net	0	0	0	0
Total expenses	40,163	46,408	135,520	153,978
Earnings from equity method investments	0	0	0	0
Operating income	8,816	7,893	15,699	15,171
Other expenses (income), net	4,720	3,419	14,179	13,974
Income (loss) from continuing operations before income taxes	4,096	4,474	1,520	1,197
Total assets (excluding intersegment receivables)	320,431		320,431
SemGas [Member]
Segment Reporting Information
Revenue	65,795	29,878	151,460	89,452
Costs of products sold, exclusive of depreciation and amortization shown below	48,403	24,068	111,141	70,607
Operating	5,436	2,931	13,869	9,092
General and administrative	1,923	1,329	5,112	4,564
Depreciation and amortization	4,992	1,797	9,353	5,153
Loss (gain) on disposal of long-lived assets, net	679	(3)	673	(3)
Total expenses	61,433	30,122	140,148	89,413
Earnings from equity method investments	0	0	0	0
Operating income	4,362	(244)	11,312	39
Other expenses (income), net	880	(378)	2,149	924
Income (loss) from continuing operations before income taxes	3,482	134	9,163	(885)
Total assets (excluding intersegment receivables)	510,129		510,129
SemLogistics [Member]
Segment Reporting Information
Revenue	2,169	2,213	7,827	8,610
Costs of products sold, exclusive of depreciation and amortization shown below	0	97	0	196
Operating	1,616	1,436	5,303	4,521
General and administrative	1,679	990	4,285	4,249
Depreciation and amortization	2,334	2,388	6,987	7,040
Loss (gain) on disposal of long-lived assets, net	0	0	0	0
Total expenses	5,629	4,911	16,575	16,006
Earnings from equity method investments	0	0	0	0
Operating income	(3,460)	(2,698)	(8,748)	(7,396)
Other expenses (income), net	(217)	337	896	1,805
Income (loss) from continuing operations before income taxes	(3,243)	(3,035)	(9,644)	(9,201)
Total assets (excluding intersegment receivables)	167,741		167,741
SemMexico [Member]
Segment Reporting Information
Revenue	65,549	62,095	160,375	193,229
Costs of products sold, exclusive of depreciation and amortization shown below	56,070	55,817	138,372	174,636
Operating	2,230	1,870	6,741	6,033
General and administrative	2,510	1,501	7,175	6,730
Depreciation and amortization	1,529	1,536	4,467	4,614
Loss (gain) on disposal of long-lived assets, net	(271)	(112)	(784)	(49)
Total expenses	62,068	60,612	155,971	191,964
Earnings from equity method investments	0	0	0	0
Operating income	3,481	1,483	4,404	1,265
Other expenses (income), net	(21)	(82)	(339)	233
Income (loss) from continuing operations before income taxes	3,502	1,565	4,743	1,032
Total assets (excluding intersegment receivables)	95,317		95,317
Corporate and Other [Member]
Segment Reporting Information
Revenue	(6,575)	(2,251)	(15,678)	(7,535)
Costs of products sold, exclusive of depreciation and amortization shown below	(6,575)	(2,251)	(15,678)	(7,535)
Operating		0	0	0
General and administrative	7,920	3,963	16,174	16,748
Depreciation and amortization	497	630	1,504	1,938
Loss (gain) on disposal of long-lived assets, net	0	0	0	0
Total expenses	1,842	2,342	2,000	11,151
Earnings from equity method investments	0	0	0	0
Operating income	(8,417)	(4,593)	(17,678)	(18,686)
Other expenses (income), net	5,536	11,075	27,358	11,214
Income (loss) from continuing operations before income taxes	(13,953)	(15,668)	(45,036)	(29,900)
Total assets (excluding intersegment receivables)	96,617		96,617
Operating Segments [Member]
Segment Reporting Information
Revenue	357,748	277,852	969,688	921,660
Operating Segments [Member] | Crude [Member]
Segment Reporting Information
Revenue	181,831	131,616	514,485	468,748
Operating Segments [Member] | SemStream [Member]
Segment Reporting Information
Revenue	0	0	0	7
Operating Segments [Member] | SemCAMS [Member]
Segment Reporting Information
Revenue	48,979	54,301	151,219	169,149
Operating Segments [Member] | SemGas [Member]
Segment Reporting Information
Revenue	59,220	27,627	135,782	81,917
Operating Segments [Member] | SemLogistics [Member]
Segment Reporting Information
Revenue	2,169	2,213	7,827	8,610
Operating Segments [Member] | SemMexico [Member]
Segment Reporting Information
Revenue	65,549	62,095	160,375	193,229
Operating Segments [Member] | Corporate and Other [Member]
Segment Reporting Information
Revenue	0	0	0
Intersegment Eliminations [Member]
Segment Reporting Information
Revenue	0	0	0	0
Intersegment Eliminations [Member] | Crude [Member]
Segment Reporting Information
Revenue	0	0	0	0
Intersegment Eliminations [Member] | SemStream [Member]
Segment Reporting Information
Revenue	0	0	0	0
Intersegment Eliminations [Member] | SemCAMS [Member]
Segment Reporting Information
Revenue	0	0	0	0
Intersegment Eliminations [Member] | SemGas [Member]
Segment Reporting Information
Revenue	6,575	2,251	15,678	7,535
Intersegment Eliminations [Member] | SemLogistics [Member]
Segment Reporting Information
Revenue	0	0	0	0
Intersegment Eliminations [Member] | SemMexico [Member]
Segment Reporting Information
Revenue	0	0	0	0
Intersegment Eliminations [Member] | Corporate and Other [Member]
Segment Reporting Information
Revenue	$ (6,575)	$ (2,251)	$ (15,678)	$ (7,535)