Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Segment Reporting Information
Revenues, External	$ 287,696	$ 312,031
Revenues, Intersegment
Total revenues	287,696	312,031
Costs of products sold, exclusive of depreciation and amortization shown below	212,369	241,521
Operating	40,771	37,991
General and administrative	17,037	19,830
Depreciation and amortization	12,636	11,725
Gain on disposal of long-lived assets, net	(162)	0
Total expenses	282,651	311,067
Earnings from equity method investments	17,345	7,498
Operating income	22,390	8,462
Other expenses (income), net	27,862	7,616
Income (loss) from continuing operations before income taxes	(5,472)	846
Total assets	1,809,208		1,748,179
SemCrude [Member]
Segment Reporting Information
Revenues, External	171,232	179,715
Revenues, Intersegment
Total revenues	171,232	179,715
Costs of products sold, exclusive of depreciation and amortization shown below	148,451	160,508
Operating	5,738	5,454
General and administrative	3,850	2,718
Depreciation and amortization	3,507	2,967
Gain on disposal of long-lived assets, net
Total expenses	161,546	171,647
Earnings from equity method investments	10,429	6,571
Operating income	20,115	14,639
Other expenses (income), net	3,171	(237)
Income (loss) from continuing operations before income taxes	16,944	14,876
Total assets	820,561
SemStream [Member]
Segment Reporting Information
Revenues, External	0	6
Revenues, Intersegment
Total revenues	0	6
Costs of products sold, exclusive of depreciation and amortization shown below		34
Operating	1	(6)
General and administrative	156	51
Depreciation and amortization	0
Gain on disposal of long-lived assets, net	6
Total expenses	163	79
Earnings from equity method investments	6,916	927
Operating income	6,753	854
Other expenses (income), net	(968)	38
Income (loss) from continuing operations before income taxes	7,721	816
Total assets	177,043
SemCAMS [Member]
Segment Reporting Information
Revenues, External	35,781	35,165
Revenues, Intersegment
Total revenues	35,781	35,165
Costs of products sold, exclusive of depreciation and amortization shown below	183	119
Operating	26,884	26,236
General and administrative	4,145	4,418
Depreciation and amortization	2,656	2,573
Gain on disposal of long-lived assets, net
Total expenses	33,868	33,346
Earnings from equity method investments
Operating income	1,913	1,819
Other expenses (income), net	4,711	5,203
Income (loss) from continuing operations before income taxes	(2,798)	(3,384)
Total assets	301,034
SemGas [Member]
Segment Reporting Information
Revenues, External	34,654	30,710
Revenues, Intersegment	4,085	2,730
Total revenues	38,739	33,440
Costs of products sold, exclusive of depreciation and amortization shown below	29,171	26,549
Operating	4,144	2,853
General and administrative	1,591	1,843
Depreciation and amortization	2,128	1,630
Gain on disposal of long-lived assets, net	(2)
Total expenses	37,032	32,875
Earnings from equity method investments
Operating income	1,707	565
Other expenses (income), net	593	532
Income (loss) from continuing operations before income taxes	1,114	33
Total assets	137,637
SemLogistics [Member]
Segment Reporting Information
Revenues, External	3,035	3,784
Revenues, Intersegment
Total revenues	3,035	3,784
Costs of products sold, exclusive of depreciation and amortization shown below
Operating	1,839	1,454
General and administrative	1,120	1,811
Depreciation and amortization	2,340	2,318
Gain on disposal of long-lived assets, net
Total expenses	5,299	5,583
Earnings from equity method investments
Operating income	(2,264)	(1,799)
Other expenses (income), net	756	1,279
Income (loss) from continuing operations before income taxes	(3,020)	(3,078)
Total assets	161,933
SemMexico [Member]
Segment Reporting Information
Revenues, External	42,994	62,651
Revenues, Intersegment
Total revenues	42,994	62,651
Costs of products sold, exclusive of depreciation and amortization shown below	38,649	57,041
Operating	2,165	2,000
General and administrative	2,222	2,688
Depreciation and amortization	1,480	1,561
Gain on disposal of long-lived assets, net	(166)
Total expenses	44,350	63,290
Earnings from equity method investments
Operating income	(1,356)	(639)
Other expenses (income), net	(471)	(110)
Income (loss) from continuing operations before income taxes	(885)	(529)
Total assets	100,675
Corporate and Other [Member]
Segment Reporting Information
Revenues, External	0
Revenues, Intersegment	(4,085)	(2,730)
Total revenues	(4,085)	(2,730)
Costs of products sold, exclusive of depreciation and amortization shown below	(4,085)	(2,730)
Operating
General and administrative	3,953	6,301
Depreciation and amortization	525	676
Gain on disposal of long-lived assets, net
Total expenses	393	4,247
Earnings from equity method investments
Operating income	(4,478)	(6,977)
Other expenses (income), net	20,070	911
Income (loss) from continuing operations before income taxes	(24,548)	(7,888)
Total assets	$ 110,325