Business Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 segment	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting [Abstract]
Number of Reportable Segments			4
Segment Reporting Information [Line Items]
Operating Revenues	$ 392,895	$ 361,979	$ 1,313,596	$ 1,157,782
Intersegment Revenues Eliminations	(2,910)	(2,363)	(7,638)	(6,292)
Total revenues	389,985	359,616	1,305,958	1,151,490
Depreciation and amortization	16,743	13,698	45,329	37,944
Operating Income (Loss) after Eliminations	12,015	12,243	52,630	58,887
Capital Expenditures	17,285	39,972	58,522	68,591
Impairment of long-lived assets	3,445	0	3,445	0
Total assets:
Total assets	1,588,736		1,588,736		1,097,919
Terminalling and storage [Member]
Segment Reporting Information [Line Items]
Operating Revenues	80,948	90,205	255,162	256,320
Intersegment Revenues Eliminations	(1,333)	(1,199)	(3,863)	(3,507)
Total revenues	79,615	89,006	251,299	252,813
Depreciation and amortization	9,512	8,532	27,902	22,925
Operating Income (Loss) after Eliminations	5,920	7,350	22,596	25,968
Capital Expenditures	9,735	33,563	39,131	59,930
Total assets:
Total assets	463,509		463,509		461,160
Natural gas services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	236,058	204,926	818,361	653,080
Intersegment Revenues Eliminations	0	0	0	0
Total revenues	236,058	204,926	818,361	653,080
Depreciation and amortization	2,684	598	3,863	1,444
Operating Income (Loss) after Eliminations	7,484	5,466	22,764	18,858
Capital Expenditures	4,611	2,398	5,185	2,513
Total assets:
Total assets	817,864		817,864		320,631
Sulfur services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	50,030	42,097	166,818	173,378
Intersegment Revenues Eliminations	0	0	0	0
Total revenues	50,030	42,097	166,818	173,378
Depreciation and amortization	2,078	2,024	6,092	5,947
Operating Income (Loss) after Eliminations	1,635	(527)	17,589	16,518
Capital Expenditures	694	2,068	3,775	2,690
Total assets:
Total assets	148,162		148,162		151,982
Marine transportation [Member]
Segment Reporting Information [Line Items]
Operating Revenues	25,859	24,751	73,255	75,004
Intersegment Revenues Eliminations	(1,577)	(1,164)	(3,775)	(2,785)
Total revenues	24,282	23,587	69,480	72,219
Depreciation and amortization	2,469	2,544	7,472	7,628
Operating Income (Loss) after Eliminations	1,455	3,733	3,895	8,813
Capital Expenditures	2,245	1,943	10,431	3,458
Impairment of long-lived assets	3,445		3,445
Total assets:
Total assets	159,201		159,201		164,146
Indirect selling, general and administrative [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0	0	0	0
Intersegment Revenues Eliminations	0	0	0	0
Total revenues	0	0	0	0
Depreciation and amortization	0	0	0	0
Operating Income (Loss) after Eliminations	(4,479)	(3,779)	(14,214)	(11,270)
Capital Expenditures	$ 0	$ 0	$ 0	$ 0