Segments (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016		Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Loss (gain) on disposal or impairment		$ 234	$ (1,685)		$ (2,176)	$ (14,992)
Revenue, Net		473,089	287,377		929,189	602,228
Depreciation and amortization		25,602	25,055		50,201	49,106
Income (Loss) from Equity Method Investments and Issuance of Common Units by Equity Method Investee		17,753	17,078		34,844	40,108
Total assets		3,166,218			3,166,218		$ 3,074,972
Income tax expense (benefit)		3,625	4,658		3,720	(16,749)
Interest Expense		13,477	18,011		27,344	35,588
Foreign currency transaction loss (gain)		(1,011)	1,543		(1,011)	3,012
Loss (gain) on sale or impairment of equity method investment		0	(9,120)		0	30,644
Other expense (income), net		(441)	(490)		(591)	(678)
Loss from discontinued operations, net of income taxes		0	2		0	4
Net income (loss)		9,611	10,787		(666)	5,894
Equity method investments		430,514			430,514		434,289
Loss on early extinguishment of debt		8	0		19,930	0
Crude Transportation [Member]
Segment Reporting Information [Line Items]
Loss (gain) on disposal or impairment					4,500
Corporate and Reconciling Items And Eliminations [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		548	496		1,039	986
Income (Loss) from Equity Method Investments and Issuance of Common Units by Equity Method Investee	[1]	6	0		9	2,191
Total assets		103,993			103,993		116,699
Income tax expense (benefit)		461	4,286		(1,466)	(18,752)
Segment profit	[2]	(10,792)	(8,008)		(17,686)	(14,168)
Equity method investments		18,942			18,942		18,933
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net		473,089	287,377		929,189	602,228
Operating Segments [Member] | Crude Transportation [Member]
Segment Reporting Information [Line Items]
Revenue, Net		14,019	15,643		27,998	32,839
Depreciation and amortization		6,498	6,174		12,425	12,034
Income (Loss) from Equity Method Investments and Issuance of Common Units by Equity Method Investee		17,747	17,078		34,835	37,917
Total assets		1,161,673			1,161,673		1,042,327
Segment profit	[2]	18,548	18,161	[3]	35,410	43,579
Equity method investments		411,572			411,572		415,356
Operating Segments [Member] | SemCAMS [Member]
Segment Reporting Information [Line Items]
Revenue, Net		60,114	33,815		96,912	64,681
Depreciation and amortization		4,434	4,294		8,930	8,245
Total assets		423,262			423,262		379,785
Income tax expense (benefit)		2,267	451		3,691	1,416
Segment profit	[2]	15,452	9,000		27,048	18,904
Operating Segments [Member] | SemGas [Member]
Segment Reporting Information [Line Items]
Revenue, Net		55,758	48,200		113,510	91,720
Depreciation and amortization		9,099	9,198		18,026	18,125
Total assets		703,094			703,094		683,952
Segment profit	[2]	16,654	12,304		32,403	11,312
Operating Segments [Member] | SemLogistics [Member]
Segment Reporting Information [Line Items]
Revenue, Net		6,968	5,932		14,496	12,312
Depreciation and amortization		1,901	1,983		3,716	3,943
Total assets		145,317			145,317		135,387
Income tax expense (benefit)		372	(273)		753	(214)
Segment profit	[2]	2,960	2,002		6,704	4,661
Operating Segments [Member] | SemMexico [Member]
Segment Reporting Information [Line Items]
Revenue, Net		35,086	30,286		68,023	60,420
Depreciation and amortization		1,022	949		1,959	1,890
Total assets		85,102			85,102		75,440
Income tax expense (benefit)		525	194		742	801
Segment profit	[2]	1,708	2,024		3,387	4,342
Operating Segments [Member] | Crude Facilities [Member]
Segment Reporting Information [Line Items]
Revenue, Net		9,825	10,300		19,460	20,433
Depreciation and amortization		2,022	1,921		3,966	3,803
Total assets		149,653			149,653		156,907
Segment profit	[2]	8,877	9,371		17,839	18,958
Operating Segments [Member] | Crude Supply and Logistics [Member]
Segment Reporting Information [Line Items]
Revenue, Net		291,319	143,201		588,790	319,823
Depreciation and amortization		78	40		140	80
Total assets		394,124			394,124		$ 484,475
Segment profit	[2]	(3,464)	10,069		(7,079)	19,162
Intersegment Eliminations [Member] | Crude Transportation [Member]
Segment Reporting Information [Line Items]
Revenue, Net		6,901	5,128		13,455	12,341
Intersegment Eliminations [Member] | SemGas [Member]
Segment Reporting Information [Line Items]
Revenue, Net		2,630	2,521		6,541	5,267
Intersegment Eliminations [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue, Net		(12,021)	(10,175)		(24,992)	(22,880)
Intersegment Eliminations [Member] | Crude Facilities [Member]
Segment Reporting Information [Line Items]
Revenue, Net		2,490	2,526		4,996	5,272
Operating segments and corporate nonsegment [Member]
Segment Reporting Information [Line Items]
Segment profit	[2]	49,943	54,923		98,026	106,750
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		25,602	25,055		50,201	49,106
Income tax expense (benefit)		3,625	4,658		3,720	(16,749)
Net unrealized loss (gain) related to derivative instruments		(928)	4,477		(901)	(71)
Interest Expense		13,477	18,011		27,344	35,588
Foreign currency transaction loss (gain)		(1,011)	1,543		(1,011)	3,012
Loss (gain) on sale or impairment of equity method investment		0	(9,120)		0	30,644
Other expense (income), net		(441)	(490)		(591)	(678)
Loss from discontinued operations, net of income taxes		$ 0	$ 2		$ 0	$ 4

[1] (1) Includes historical earnings from equity method investments including gain (loss) on issuance of common units by equity method investee related to our investment in NGL Energy.

[2] (1) Segment profit (loss) represents revenues excluding unrealized gains (losses) related to derivative instruments plus earnings from equity method investments less cost of sales excluding depreciation and amortization and less operating and general and administrative expenses, including gains or losses on disposals or impairments.

[3] (2) The six months ended June 30, 2017, includes a $4.5 million out of period loss on the disposal of right-of-way related to immaterial prior period errors.