Discontinued Operations Discontinued Operations (Notes) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total costs and expenses	$ 539,045	$ 424,182	$ 493,307
(Gains) Losses on asset dispositions and impairments, net	11,637	(25,983)	14,609
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(23,637)	(119,221)	(8,678)
SEACOR Marine Holdings Inc. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue	62,291	215,636	368,868
Disposal Group, Including Discontinued Operation, Operating Expense	65,888	166,925	275,972
Disposal Group, Including Discontinued Operation, General and Administrative Expense	29,682	49,308	53,085
Depreciation and Amortization, Discontinued Operations	22,181	58,069	61,729
Total costs and expenses	117,751	274,302	390,786
(Gains) Losses on asset dispositions and impairments, net	4,219	(116,222)	(17,017)
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	(51,241)	(174,888)	(38,935)
Disposal Group, Including Discontinued Operation, Other Expense	(1,780)	(15,417)	(13,641)
Discontinued Operation, Tax Effect of Discontinued Operation	(12,931)	(63,468)	(16,973)
Income (Loss) from Ongoing Equity Method Investment in Discontinued Operation after Disposal	1,663	(6,314)	8,757
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(34,867)	(133,151)	(26,846)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest	(1,892)	(1,103)	403
Illinois Corn Processing Llc [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue	78,061	177,401	166,905
Disposal Group, Including Discontinued Operation, Operating Expense	76,306	158,495	143,967
Disposal Group, Including Discontinued Operation, General and Administrative Expense	2,140	3,011	2,307
Depreciation and Amortization, Discontinued Operations	2,354	4,299	3,902
Total costs and expenses	80,800	165,805	150,176
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	(2,739)	11,596	16,729
Disposal Group, Including Discontinued Operation, Other Expense	(20,557)	(4,520)	(6,150)
Discontinued Operation, Tax Effect of Discontinued Operation	7,818	4,901	5,133
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	10,000	11,215	17,746
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest	(539)	3,688	5,862
Intersegment Eliminations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue	(1,176)	(2,517)	(3,024)
Disposal Group, Including Discontinued Operation, Operating Expense	(1,289)	(2,862)	(2,942)
Disposal Group, Including Discontinued Operation, General and Administrative Expense	(42)	(100)	(124)
Total costs and expenses	(1,331)	(2,962)	(3,066)
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	155	445	42
Disposal Group, Including Discontinued Operation, Other Expense	(1,738)	(3,732)	(608)
Discontinued Operation, Tax Effect of Discontinued Operation	663	1,462	228
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 1,230	$ 2,715	$ 422