Segment Information (Financial Information) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total revenues	$ 578,602	$ 735,904	$ 1,046,641	$ 1,343,300
Operating Income (Loss)	24,491	21,031	45,929	38,592
Nonoperating Income (Expense)	(6,400)	(6,230)	(13,570)	(10,177)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	18,091	14,801	32,359	28,415
Depreciation and amortization	7,325	6,670	14,469	12,562
Payments to Acquire Productive Assets	8,328	14,846	14,569	41,490
Assets	483,221	563,748	483,221	563,748	$ 500,951
Logistics Segment [Member]
Segment Reporting Information [Line Items]
Revenues: Affiliate	43,053	36,279	83,969	71,054
Revenues: Third-party	677	679	1,367	1,302
Total revenues	43,730	36,958	85,336	72,356
Operating Income (Loss)	18,751	12,003	32,681	23,355
Depreciation and amortization	6,119	5,563	12,080	10,378
Payments to Acquire Productive Assets	7,299	13,847	13,168	37,444
Assets	309,137	297,566	309,137	297,566
Wholesale Segment [Member]
Segment Reporting Information [Line Items]
Revenues: Affiliate	137,437	175,762	245,978	319,236
Revenues: Third-party	397,435	523,184	715,327	951,708
Total revenues	534,872	698,946	961,305	1,270,944
Operating Income (Loss)	8,797	12,171	18,750	21,160
Depreciation and amortization	1,206	1,107	2,389	2,184
Payments to Acquire Productive Assets	1,029	999	1,401	4,046
Assets	156,067	185,523	156,067	185,523
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)	(3,057)	(3,143)	(5,502)	(5,923)
Assets	$ 18,017	$ 80,659	$ 18,017	$ 80,659