Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Activities by Segment [Abstract]
Revenues	$ 1,159,931	$ 965,098	$ 2,109,120	$ 1,917,533
Depreciation Depletion and Amortization	6,109	5,245	12,215	10,774
Segment operating earnings [Abstract]
General and administrative expenses	(2,147)	(2,431)	(4,401)	(4,463)
Operating earnings	6,076	10,458	14,488	23,127
Interest income	45	32	87	70
Interest expense	0	(21)	0	(23)
Earnings from continuing operations before income taxes	6,121	10,469	14,575	23,174
Identifiable assets by segment [Abstract]
Assets	483,144		483,144		448,082
Operating Segments [Member]
Activities by Segment [Abstract]
Revenues	1,159,931	965,098	2,109,120	1,917,533
Segment operating earnings (loss)	8,223	12,889	18,889	27,590
Depreciation Depletion and Amortization	6,109	5,245	12,215	10,774
Property and Equipment Additions	4,319	12,395	12,089	16,298
Segment operating earnings [Abstract]
Segment operating earnings (loss)	8,223	12,889	18,889	27,590
General and administrative expenses	(2,147)	(2,431)	(4,401)	(4,463)
Operating earnings	6,076	10,458	14,488	23,127
Interest income	45	32	87	70
Interest expense	0	(21)	0	(23)
Earnings from continuing operations before income taxes	6,121	10,469	14,575	23,174
Identifiable assets by segment [Abstract]
Assets	483,144		483,144		448,082
Marketing [Member] | Operating Segments [Member]
Activities by Segment [Abstract]
Revenues	1,139,004	943,843	2,066,208	1,875,719
Segment operating earnings (loss)	7,776	10,681	17,146	24,115
Depreciation Depletion and Amortization	2,287	1,814	4,556	3,578
Property and Equipment Additions	1,855	7,219	5,931	8,580
Segment operating earnings [Abstract]
Segment operating earnings (loss)	7,776	10,681	17,146	24,115
Identifiable assets by segment [Abstract]
Assets	354,784		354,784		306,693
Transportation [Member] | Operating Segments [Member]
Activities by Segment [Abstract]
Revenues	17,303	17,543	34,952	34,889
Segment operating earnings (loss)	955	1,833	2,130	3,231
Depreciation Depletion and Amortization	1,818	1,740	3,631	3,476
Property and Equipment Additions	226	1,428	429	1,573
Segment operating earnings [Abstract]
Segment operating earnings (loss)	955	1,833	2,130	3,231
Identifiable assets by segment [Abstract]
Assets	32,841		32,841		34,406
Oil and Gas [Member] | Operating Segments [Member]
Activities by Segment [Abstract]
Revenues	3,624	3,712	7,960	6,925
Segment operating earnings (loss)	(508)	375	(387)	244
Depreciation Depletion and Amortization	2,004	1,691	4,028	3,720
Property and Equipment Additions	2,238	3,748	5,729	6,145
Segment operating earnings [Abstract]
Segment operating earnings (loss)	(508)	375	(387)	244
Identifiable assets by segment [Abstract]
Assets	37,095		37,095		37,093
Other [Member] | Operating Segments [Member]
Identifiable assets by segment [Abstract]
Assets	$ 58,424		$ 58,424		$ 69,890