Basis of Presentation and Accounting Policies Earning Per Common Share (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net Income (Loss) attributable to SEACOR Holdings Inc.	$ (39,803,000)	$ 6,965,000	$ (122,148,000)	$ (11,917,000)
Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units	0	0	0	0
Dilutive Securities, Effect on Basic Earnings Per Share, Dilutive Convertible Securities	0	0	0	0
Net Income (Loss) Available to Common Stockholders, Diluted	$ (39,803,000)	$ 6,965,000	$ (122,148,000)	$ (11,917,000)
Weighted Average Number of Shares Outstanding, Basic	16,943,647	17,294,927	16,896,751	17,616,035
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	266,180	0	0
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	0	0	0	0
Weighted Average Number of Shares Outstanding, Diluted	16,943,647	17,561,107	16,896,751	17,616,035
Basic Earnings (Loss) Per Common Share of SEACOR Holdings Inc.	$ (2.35)	$ 0.40	$ (7.23)	$ (0.68)
Diluted Earnings (Loss) Per Common Share of SEACOR Holdings Inc.	$ (2.35)	$ 0.40	$ (7.23)	$ (0.68)
Stock Compensation Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,041,652	846,934	2,041,652	2,038,450
Two Point Five Percentage Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,382,626		4,200,525
Three Point Zero Percentage Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,825,326		1,825,326
Three Point Seven Five Percentage Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,243,500
Three Point Seven Five Percentage Convertible Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.75%		3.75%
Three Point Seven Five Percentage Convertible Notes [Member] \| Convertible Debt Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			2,243,500
Three Point Zero Percentage Convertible Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.00%		3.00%
Three Point Zero Percentage Convertible Notes [Member] \| Convertible Debt Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			1,825,326
Two Point Five Percentage Convertible Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage	2.50%		2.50%
Two Point Five Percentage Convertible Notes [Member] \| Convertible Debt Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			2,910,688

Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise of stock options or restrictive stock units (RSUs).

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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