Segments (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information
Revenue		$ 382,493	$ 397,065	$ 377,226	$ 298,310	$ 547,237	$ 594,235	$ 482,224	$ 498,883	$ 1,455,094	$ 2,122,579	$ 1,427,016
Earnings from equity method investments		20,687	16,237	23,903	20,559	15,827	14,223	19,187	14,962	81,386	64,199	52,477
Depreciation and amortization expense										100,882	98,397	66,409
Income tax expense (benefit)		3,921	10,006	14,861	4,742	12,569	24,090	(6,672)	16,526	33,530	46,513	(17,254)
Total assets		2,870,690				2,589,802				2,870,690	2,589,802
Equity method investments		551,078				577,920				551,078	577,920
Unrealized Gain (Loss) on Derivatives										2,014	(1,734)	(974)
Interest Income (Expense), Net										69,675	49,044	25,142
Foreign Currency Transaction Gain (Loss), before Tax										(1,067)	(86)	(1,633)
Other Nonoperating Income (Expense)										(15,801)	(20,536)	45,906
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest		1	1	2	0	(4)	0	0	5	4	1	(59)
Net income (loss)		(977)	$ 9,580	$ 28,433	$ 5,776	12,707	$ 32,196	$ (12,584)	$ 19,738	42,812	52,057	65,812
Crude Transportation [Member]
Segment Reporting Information
Earnings from equity method investments										76,355	61,856	45,354
Depreciation and amortization expense										35,500	33,679	17,814
Segment profit	[1]									81,028	76,705	51,100
Additions to long-lived assets										219,227	160,471	244,777
Total assets		877,017				746,723				877,017	746,723
Equity method investments		438,291				415,674				438,291	415,674
Crude Facilities [Member]
Segment Reporting Information
Depreciation and amortization expense										5,829	5,365	4,833
Segment profit	[1]									33,757	32,286	37,083
Additions to long-lived assets										30,118	8,207	11,783
Total assets		155,186				116,784				155,186	116,784
Crude Supply and Logistics [Member]
Segment Reporting Information
Depreciation and amortization expense										159	549	673
Segment profit	[1]									30,088	24,021	15,010
Additions to long-lived assets										2,564	11,662	1,868
Total assets		328,419				271,444				328,419	271,444
SemGas [Member]
Segment Reporting Information
Depreciation and amortization expense										31,803	26,353	14,517
Segment profit	[1]									61,669	41,715	32,483
Additions to long-lived assets										110,908	153,088	410,508
Total assets		719,789				662,223				719,789	662,223
SemCAMS [Member]
Segment Reporting Information
Depreciation and amortization expense										12,940	14,295	10,766
Income tax expense (benefit)										4,847	3,135	6,348
Segment profit	[1]									36,013	45,326	32,886
Additions to long-lived assets										142,368	35,286	56,122
Total assets		331,749				279,191				331,749	279,191
SemLogistics [Member]
Segment Reporting Information
Depreciation and amortization expense										8,543	10,005	9,426
Income tax expense (benefit)										(2,195)	(2,231)	(5,699)
Segment profit	[1]									7,249	25	(2,007)
Additions to long-lived assets										12,289	2,974	2,071
Total assets		155,794				150,498				155,794	150,498
SemMexico [Member]
Segment Reporting Information
Depreciation and amortization expense										4,076	6,031	5,991
Income tax expense (benefit)										2,611	4,053	2,589
Segment profit	[1]									15,614	16,139	13,493
Additions to long-lived assets										7,051	9,690	6,375
Total assets		89,608				107,225				89,608	107,225
SemStream [Member]
Segment Reporting Information
Earnings from equity method investments										11,416	31,363	33,996
Segment profit	[1]									11,391	31,280	33,389
Additions to long-lived assets										0	0	18,775
Total assets		112,787				162,246				112,787	162,246
Equity method investments		112,787				162,246				112,787	162,246
Corporate, Non-Segment [Member]
Segment Reporting Information
Depreciation and amortization expense										2,032	2,120	2,389
Income tax expense (benefit)										28,267	41,556	(20,492)
Segment profit	[1]									(44,760)	(43,841)	(30,088)
Additions to long-lived assets										1,919	1,906	1,211
Total assets		100,947				93,468				100,947	93,468
Operating Segments [Member]
Segment Reporting Information
Earnings from equity method investments										87,771	93,219	79,350
Depreciation and amortization expense										100,882	98,397	66,409
Income tax expense (benefit)										33,530	46,513	(17,254)
Segment profit	[1]									232,049	223,656	183,349
Additions to long-lived assets										526,444	383,284	753,490
Total assets		$ 2,871,296				$ 2,589,802				2,871,296	2,589,802
Operating Segments [Member]
Segment Reporting Information
Revenue										1,455,094	2,122,579	1,427,016
Operating Segments [Member] | Crude Transportation [Member]
Segment Reporting Information
Revenue										81,991	84,718	34,917
Operating Segments [Member] | Crude Facilities [Member]
Segment Reporting Information
Revenue										45,936	44,007	46,697
Operating Segments [Member] | Crude Supply and Logistics [Member]
Segment Reporting Information
Revenue										716,784	1,169,372	685,588
Operating Segments [Member] | SemGas [Member]
Segment Reporting Information
Revenue										231,569	342,286	207,134
Operating Segments [Member] | SemCAMS [Member]
Segment Reporting Information
Revenue										136,197	176,724	198,450
Operating Segments [Member] | SemLogistics [Member]
Segment Reporting Information
Revenue										24,351	12,650	11,671
Operating Segments [Member] | SemMexico [Member]
Segment Reporting Information
Revenue										211,291	290,869	242,559
Operating Segments [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information
Revenue										6,975	1,953	0
Intersegment Eliminations [Member] | Crude Transportation [Member]
Segment Reporting Information
Revenue										15,021	10,840	225
Intersegment Eliminations [Member] | SemGas [Member]
Segment Reporting Information
Revenue										20,605	37,897	23,985
Intersegment Eliminations [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information
Revenue										$ (35,626)	$ (48,737)	$ (24,210)

[1] (1) Segment profit 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.