Condensed Consolidated Statements Of Income (Loss) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Operating Revenues	$ 115,791,000	$ 99,647,000	$ 234,205,000	$ 204,699,000
Costs and Expenses [Abstract]
Operating	69,686,000	64,027,000	144,898,000	127,063,000
Administrative and general	25,540,000	21,361,000	48,418,000	44,037,000
Depreciation and amortization	17,469,000	15,043,000	34,188,000	30,141,000
Total costs and expenses	112,695,000	100,431,000	227,504,000	201,241,000
Gains on Asset Dispositions and Impairments, Net	5,897,000	2,586,000	5,709,000	3,183,000
Operating Loss	8,993,000	1,802,000	12,410,000	6,641,000
Other Income (Expense):
Interest income	2,150,000	4,179,000	4,284,000	8,608,000
Interest expense	11,676,000	10,258,000	21,980,000	19,937,000
Debt extinguishment gains, net	(97,000)	1,615,000	(97,000)	4,838,000
Marketable security gains (losses), net	(21,674,000)	(21,459,000)	(838,000)	(42,970,000)
Derivative gains, net	16,897,000	(2,574,000)	19,727,000	(2,665,000)
Foreign currency gains, net	(1,470,000)	797,000	(71,000)	2,394,000
Other, net	424,000	(7,652,000)	4,000	(7,649,000)
Total Other Nonoperating Income (Expense)	(15,446,000)	(35,352,000)	1,029,000	(57,381,000)
Income (Loss) Before Income Tax Expense (Benefit) and Equity in Earnings (Losses) of 50% or Less Owned Companies	(6,453,000)	(33,550,000)	13,439,000	(50,740,000)
Income Tax Expense (Benefit)	(3,664,000)	(13,633,000)	232,000	(22,757,000)
Income (Loss) Before Equity in Earnings (Losses) of 50% or Less Owned Companies	(2,789,000)	(19,917,000)	13,207,000	(27,983,000)
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	2,333,000	(3,847,000)	2,441,000	(6,057,000)
Net Income (Loss)	(456,000)	(23,764,000)	15,648,000	(34,040,000)
Loss from Discontinued Operations, Net of Tax	(28,629,000)	(27,169,000)	(34,077,000)	(37,417,000)
Net Loss	(29,085,000)	(50,933,000)	(18,429,000)	(71,457,000)
Net Income Attributable to Noncontrolling Interests in Subsidiaries	3,723,000	4,226,000	10,296,000	10,888,000
Net Loss attributable to SEACOR Holdings Inc.	$ (32,808,000)	$ (55,159,000)	$ (28,725,000)	$ (82,345,000)
Basic Earnings (Loss) Per Common Share of SEACOR Holdings Inc.:
Continuing operations	$ (0.39)	$ (1.61)	$ 0.17	$ (2.63)
Discontinued operations	(1.52)	(1.65)	(1.85)	(2.25)
Basic Earnings (Loss) Per Common Share of SEACOR Holdings Inc.	(1.91)	(3.26)	(1.68)	(4.88)
Diluted Earnings (Loss) Per Common Share of SEACOR Holdings Inc.:
Continuing operations	(0.39)	(1.61)	0.17	(2.63)
Discontinued operations	(1.52)	(1.65)	(1.82)	(2.25)
Diluted Earnings (Loss) Per Common Share of SEACOR Holdings Inc.	$ (1.91)	$ (3.26)	$ (1.65)	$ (4.88)
Weighted Average Common Shares Outstanding:
Basic	17,207,831	16,928,722	17,141,306	16,873,045
Diluted	17,207,831	16,928,722	17,440,361	16,873,045