Segment Information (Financial Information) (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]
Total revenues	$ 627,509	$ 578,602	$ 1,232,201	$ 1,046,641
Operating Income (Loss)	25,039	16,597	51,401	29,785
Nonoperating Income (Expense)	(6,561)	(6,400)	(13,147)	(13,570)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	18,478	10,197	38,254	16,215
Depreciation and amortization	9,784	9,553	19,516	18,891
Payments to Acquire Productive Assets			14,317	16,088
Assets	564,871	588,956	564,871	588,956	$ 580,854
Operating Segments [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	9,784	9,553	19,516	18,891
Payments to Acquire Productive Assets	8,847	7,732	14,317	16,088
Operating Segments [Member] | Logistics Segment [Member]
Segment Reporting Information [Line Items]
Revenues: Affiliate	53,567	43,053	103,204	83,969
Revenues: Third-party	703	677	1,322	1,367
Total revenues	54,270	43,730	104,526	85,336
Operating Income (Loss)	17,611	11,064	32,641	16,977
Depreciation and amortization	8,781	8,347	17,362	16,502
Payments to Acquire Productive Assets	8,703	6,703	14,154	14,687
Assets	411,581	414,872	411,581	414,872
Operating Segments [Member] | Wholesale Segment [Member]
Segment Reporting Information [Line Items]
Revenues: Affiliate	153,986	137,437	294,893	245,978
Revenues: Third-party	419,253	397,435	832,782	715,327
Total revenues	573,239	534,872	1,127,675	961,305
Operating Income (Loss)	13,180	8,797	28,154	18,750
Depreciation and amortization	1,003	1,206	2,154	2,389
Payments to Acquire Productive Assets	144	1,029	163	1,401
Assets	126,345	156,067	126,345	156,067
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)	(5,752)	(3,264)	(9,394)	(5,942)
Assets	$ 26,945	$ 18,017	$ 26,945	$ 18,017