Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenue	$ 498,883	$ 287,696
Costs of products sold, exclusive of depreciation and amortization shown below	385,113	212,369
Operating	50,778	40,771
General and administrative	18,736	17,037
Depreciation and amortization	23,637	12,636
Gain on disposal of long-lived assets, net	(58)	(162)
Total expenses	478,206	282,651
Earnings from equity method investments	14,962	17,345
Gain on issuance of common units by equity method investee	8,127	0
Operating income	43,766	22,390
Other expenses (income), net	7,497	27,862
Income (loss) from continuing operations before income taxes	36,269	(5,472)
Total assets at March 31, 2014 (excluding intersegment receivables)	2,561,394		2,470,614
Crude [Member]
Segment Reporting Information [Line Items]
Revenue	292,514	171,232
Costs of products sold, exclusive of depreciation and amortization shown below	254,537	148,451
Operating	15,139	5,738
General and administrative	3,942	3,850
Depreciation and amortization	11,482	3,507
Gain on disposal of long-lived assets, net	(34)
Total expenses	285,066	161,546
Earnings from equity method investments	11,371	10,429
Gain on issuance of common units by equity method investee	0
Operating income	18,819	20,115
Other expenses (income), net	4,663	3,171
Income (loss) from continuing operations before income taxes	14,156	16,944
Total assets at March 31, 2014 (excluding intersegment receivables)	1,116,662
SemStream [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Costs of products sold, exclusive of depreciation and amortization shown below	0	0
Operating	0	1
General and administrative	113	156
Depreciation and amortization	0	0
Gain on disposal of long-lived assets, net	0	6
Total expenses	113	163
Earnings from equity method investments	3,591	6,916
Gain on issuance of common units by equity method investee	8,127
Operating income	11,605	6,753
Other expenses (income), net	(1,264)	(968)
Income (loss) from continuing operations before income taxes	12,869	7,721
Total assets at March 31, 2014 (excluding intersegment receivables)	215,225
SemCAMS [Member]
Segment Reporting Information [Line Items]
Revenue	39,283	35,781
Costs of products sold, exclusive of depreciation and amortization shown below	67	183
Operating	23,666	26,884
General and administrative	3,980	4,145
Depreciation and amortization	2,829	2,656
Gain on disposal of long-lived assets, net	0	0
Total expenses	30,542	33,868
Earnings from equity method investments	0	0
Gain on issuance of common units by equity method investee	0
Operating income	8,741	1,913
Other expenses (income), net	4,155	4,711
Income (loss) from continuing operations before income taxes	4,586	(2,798)
Total assets at March 31, 2014 (excluding intersegment receivables)	294,405
SemGas [Member]
Segment Reporting Information [Line Items]
Revenue	100,578	38,739
Costs of products sold, exclusive of depreciation and amortization shown below	78,582	29,171
Operating	7,444	4,144
General and administrative	1,972	1,591
Depreciation and amortization	4,969	2,128
Gain on disposal of long-lived assets, net	4	(2)
Total expenses	92,971	37,032
Earnings from equity method investments	0	0
Gain on issuance of common units by equity method investee	0
Operating income	7,607	1,707
Other expenses (income), net	1,689	593
Income (loss) from continuing operations before income taxes	5,918	1,114
Total assets at March 31, 2014 (excluding intersegment receivables)	594,878
SemLogistics [Member]
Segment Reporting Information [Line Items]
Revenue	4,790	3,035
Costs of products sold, exclusive of depreciation and amortization shown below	350
Operating	2,080	1,839
General and administrative	1,422	1,120
Depreciation and amortization	2,495	2,340
Gain on disposal of long-lived assets, net	0	0
Total expenses	6,347	5,299
Earnings from equity method investments	0	0
Gain on issuance of common units by equity method investee	0
Operating income	(1,557)	(2,264)
Other expenses (income), net	251	756
Income (loss) from continuing operations before income taxes	(1,808)	(3,020)
Total assets at March 31, 2014 (excluding intersegment receivables)	168,751
SemMexico [Member]
Segment Reporting Information [Line Items]
Revenue	71,610	42,994
Costs of products sold, exclusive of depreciation and amortization shown below	61,469	38,649
Operating	2,449	2,165
General and administrative	2,751	2,222
Depreciation and amortization	1,427	1,480
Gain on disposal of long-lived assets, net	(28)	(166)
Total expenses	68,068	44,350
Earnings from equity method investments	0	0
Gain on issuance of common units by equity method investee	0
Operating income	3,542	(1,356)
Other expenses (income), net	(45)	(471)
Income (loss) from continuing operations before income taxes	3,587	(885)
Total assets at March 31, 2014 (excluding intersegment receivables)	109,518
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue	(9,892)	(4,085)
Costs of products sold, exclusive of depreciation and amortization shown below	(9,892)	(4,085)
Operating		0
General and administrative	4,556	3,953
Depreciation and amortization	435	525
Gain on disposal of long-lived assets, net	0	0
Total expenses	(4,901)	393
Earnings from equity method investments	0	0
Gain on issuance of common units by equity method investee	0
Operating income	(4,991)	(4,478)
Other expenses (income), net	(1,952)	20,070
Income (loss) from continuing operations before income taxes	(3,039)	(24,548)
Total assets at March 31, 2014 (excluding intersegment receivables)	61,955
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	498,883	287,696
Operating Segments [Member] | Crude [Member]
Segment Reporting Information [Line Items]
Revenue	292,514	171,232
Operating Segments [Member] | SemStream [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Operating Segments [Member] | SemCAMS [Member]
Segment Reporting Information [Line Items]
Revenue	39,283	35,781
Operating Segments [Member] | SemGas [Member]
Segment Reporting Information [Line Items]
Revenue	90,686	34,654
Operating Segments [Member] | SemLogistics [Member]
Segment Reporting Information [Line Items]
Revenue	4,790	3,035
Operating Segments [Member] | SemMexico [Member]
Segment Reporting Information [Line Items]
Revenue	71,610	42,994
Operating Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Intersegment Eliminations [Member] | Crude [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Intersegment Eliminations [Member] | SemStream [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Intersegment Eliminations [Member] | SemCAMS [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Intersegment Eliminations [Member] | SemGas [Member]
Segment Reporting Information [Line Items]
Revenue	9,892	4,085
Intersegment Eliminations [Member] | SemLogistics [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Intersegment Eliminations [Member] | SemMexico [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Intersegment Eliminations [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue	$ (9,892)	$ (4,085)