Basis of Presentation and Accounting Policies Earning Per Common Share (Details) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017
Net income attributable to SEACOR Holdings Inc.	$ (32,808,000)	$ (55,159,000)	$ (28,725,000)	$ (82,345,000)
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	$ (32,808,000)	$ (55,159,000)	$ (28,725,000)	$ (82,345,000)
Weighted Average Number of Shares Outstanding, Basic	17,207,831	16,928,722	17,141,306	16,873,045
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	0	299,055	0
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	0	0	0	0
Weighted Average Number of Shares Outstanding, Diluted	17,207,831	16,928,722	17,440,361	16,873,045
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.	$ (1.91)	$ (3.26)	$ (1.65)	$ (4.88)
Stock Compensation Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,644,489	2,024,421	1,563,901	2,024,421
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		2,243,500
Three Point Zero Percentage Convertible Notes [Member]
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities			2,801,147
Debt Instrument, Interest Rate, Stated Percentage	3.00%		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	2,801,147	1,825,326	2,801,147	1,825,326
Two Point Five Percentage Convertible Notes [Member]
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities			2,001,993
Debt Instrument, Interest Rate, Stated Percentage	2.50%		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	2,693,475	2,975,847	2,793,144	3,177,620

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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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise of dilutive convertible securities excluding adjustments related to ESOP convertible preferred stock, stock options, and restrictive stock units.

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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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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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