SEACOR Marine (SMHI) 10-K 12 Mar 19 2018 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Mar. 01, 2019	Jun. 29, 2018
Document Information [Line Items]
Entity Registrant Name	SEACOR Marine Holdings Inc.
Entity Central Index Key	0001690334
Trading Symbol	smhi
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Emerging Growth Company	true
Entity Small Business	false
Entity Common Stock, Shares Outstanding (in shares)		21,043,080
Entity Public Float			$ 437,851,121
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Shell Company	false
Entity Ex Transition Period	true

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents		$ 95,195	$ 110,234
Restricted cash		1,657	2,317
Receivables:
Trade, net of allowance for doubtful accounts of $860 and $4,039 in 2018 and 2017, respectively		64,125	45,616
Other		12,082	12,341
Inventories		3,443	3,756
Prepaid expenses and other		2,530	3,026
Total current assets		179,032	177,290
Property and Equipment:
Historical cost	[1]	1,242,733	1,179,836
Accumulated depreciation		(561,272)	(560,160)
		681,461	619,676
Construction in progress		88,918	70,157
Net property and equipment		770,379	689,833
Investments, at Equity, and Advances to 50% or Less Owned Companies		121,773	92,169
Construction Reserve Funds		28,061	45,361
Other Assets		3,690	3,851
		1,102,935	1,008,504
Current Liabilities:
Current portion of long-term debt		16,812	22,858
Accounts payable and accrued expenses		19,370	24,024
Due to SEACOR Holdings		452	1,358
Accrued wages and benefits		5,025	5,087
Accrued income taxes		1,917	4,290
Accrued capital, repair and maintenance expenditures		18,886	19,618
Deferred revenues		1,327	10,104
Other current liabilities		19,828	11,879
Total current liabilities		83,617	99,218
Long-Term Debt		387,854	292,041
Conversion Option Liability on Convertible Senior Notes		5,276	6,832
Deferred Income Taxes		44,682	55,506
Deferred Gains and Other Liabilities		26,571	31,741
Total liabilities		548,000	485,338
SEACOR Marine Holdings Inc. stockholders' equity:
Preferred stock, $.01 par value, 10,000,000 shares authorized; none issued nor outstanding
Common stock, $.01 par value, 60,000,000 shares authorized; 20,443,215 and 17,675,356 shares issued in 2018 and 2017, respectively		204	177
Additional paid-in capital		415,372	303,996
Retained earnings		126,834	216,511
Shares held in treasury of 4,007 and 0 in 2018 and 2017, respectively, at cost		(91)
Accumulated other comprehensive loss, net of tax		(16,788)	(12,493)
		525,531	508,191
Noncontrolling interests in subsidiaries		29,404	14,975
Total equity		554,935	523,166
		$ 1,102,935	$ 1,008,504
[1]	Includes property and equipment acquired in business acquisitions at acquisition date fair value, and net of the impact of recognized impairment charges.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Trade receivables, allowance for doubtful accounts	$ 860	$ 4,039
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	60,000,000	60,000,000
Common stock, shares issued (in shares)	20,443,215	17,675,356
Shares held in treasury (in shares)	4,007	0

Consolidated Statements of Loss

Consolidated Statements of Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Revenues	$ 253,609	$ 173,783	$ 215,636
Costs and Expenses:
Operating	186,566	159,599	166,925
Administrative and general	52,813	56,217	49,308
Depreciation and amortization	72,246	62,779	58,069
	311,625	278,595	274,302
Losses on Asset Dispositions and Impairments, Net	(8,747)	(23,547)	(116,222)
Operating Loss	(66,763)	(128,359)	(174,888)
Other Income (Expense):
Interest income	1,234	1,805	4,458
Interest expense	(27,869)	(16,532)	(10,008)
SEACOR Holdings management fees		(3,208)	(7,700)
SEACOR Holdings guarantee fees	(29)	(201)	(315)
Loss on Debt Extinguishment	(638)
Marketable security gains (losses), net		10,931	(45)
Derivative gains, net	2,854	20,256	2,995
Foreign currency losses, net	(1,447)	(1,709)	(3,312)
Other, net	674	(6)	(1,490)
	(25,221)	11,336	(15,417)
Loss Before Income Tax Benefit and Equity in Earnings (Losses) of 50% or Less Owned Companies	(91,984)	(117,023)	(190,305)
Current	9,390	(13,400)	(15,421)
Deferred income tax benefit	(22,737)	(61,006)	(48,048)
	(13,347)	(74,406)	(63,469)
Loss Before Equity in (Losses) Earnings of 50% or Less Owned Companies	(78,637)	(42,617)	(126,836)
Equity in (Losses) Earnings of 50% or Less Owned Companies, Net of Tax	(3,415)	4,077	(6,314)
Net Loss	(82,052)	(38,540)	(133,150)
Net Loss attributable to Noncontrolling Interests in Subsidiaries	(4,444)	(5,639)	(1,103)
Net Loss attributable to SEACOR Marine Holdings Inc.	$ (77,608)	$ (32,901)	$ (132,047)
Basic and Diluted Loss Per Common Share of SEACOR Marine Holdings Inc. (in dollars per share)	$ (3.71)	$ (1.87)	$ (7.47)
Basic and Diluted Weighted Average Common Shares Outstanding: (in shares)	20,926,307	17,601,244	17,671,356

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Loss	$ (82,052)	$ (38,540)	$ (133,150)
Other Comprehensive Loss:
Foreign currency translation (losses) gains, net	(2,365)	4,654	(9,510)
Reclassification of foreign currency translation losses to foreign currency losses, net			74
Derivative (losses) gains on cash flow hedges	(1,939)	214	(2,493)
Other comprehensive income	(4,349)	5,375	(9,167)
Income tax (expense) benefit	(46)	(6,256)	2,823
Other comprehensive income, net	(4,395)	(881)	(6,344)
Comprehensive Loss	(86,447)	(39,421)	(139,494)
Comprehensive Loss attributable to Noncontrolling Interests in Subsidiaries	(4,544)	(5,364)	(2,205)
Comprehensive Loss attributable to SEACOR Marine Holdings Inc.	(81,903)	(34,057)	(137,289)
Interest Expense [Member]
Other Comprehensive Loss:
Reclassification of derivative losses on cash flow hedges	31	118	18
Reclassification of derivative losses on cash flow hedges	(31)	(118)	(18)
Equity Method Investments [Member]
Other Comprehensive Loss:
Reclassification of derivative losses on cash flow hedges	76	(389)	(2,744)
Reclassification of derivative losses on cash flow hedges	$ (76)	$ 389	$ 2,744

Consolidated Statements of Chan

Consolidated Statements of Changes In Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]	Total
Balance (in shares)	17,671,356
Balance (in shares) at Dec. 31, 2015	17,671,356
Balance at Dec. 31, 2015	$ 177	$ 306,359		$ 381,459	$ (6,095)	$ 7,954	$ 689,854
Distributions to noncontrolling interests						(205)	(205)
Net loss				(132,047)		(1,103)	(133,150)
Other comprehensive income (loss)					(5,242)	(1,102)	(6,344)
Balance (in shares)	17,671,356
Balance at Dec. 31, 2016	$ 177	306,359		249,412	(11,337)	5,544	550,155
Balance (in shares)	17,671,356
Balance (in shares) at Dec. 31, 2016	17,671,356
Net loss				(32,901)		(5,639)	(38,540)
Other comprehensive income (loss)					(1,156)	275	(881)
Distribution of SEACOR Marine restricted stock to Company personnel by SEACOR Holdings (in shares)	1,000
Distribution of SEACOR Marine restricted stock to Company personnel by SEACOR Holdings		(2,656)					(2,656)
Director share awards (in shares)	3,000
Director share awards		681					681
Amortization of employee share awards		726					726
Purchase of subsidiary shares from noncontrolling interests, net of tax		(1,114)				(2,579)	(3,693)
Consolidation of 50% or less owned companies						17,374	$ 17,374
Exercise of options (in shares)
Balance (in shares)	17,671,356
Balance at Dec. 31, 2017	$ 177	303,996		216,511	(12,493)	14,975	$ 523,166
Balance (in shares)	17,675,356
Balance (in shares) at Dec. 31, 2017	17,675,356
Net loss				(77,608)		(4,444)	(82,052)
Other comprehensive income (loss)					(4,295)	(100)	(4,395)
Director share awards (in shares)
Director share awards		893					893
Amortization of employee share awards		3,494					3,494
Impact of adoption of accounting principle at Dec. 31, 2017				(12,069)			(12,069)
Balance at Dec. 31, 2017	$ 177	303,996		204,442	(12,493)	14,975	511,097
Issuance of Common Stock (in shares)	2,291,084
Issuance of Common Stock	$ 23	42,973					42,996
Issuance of Warrants		62,809					$ 62,809
Exercise of options (in shares)	66,625						66,625
Exercise of options	$ 1	832					$ 833
Exercise of Warrants (in shares)	289,442		108
Exercise of Warrants	$ 3		$ (3)
Restricted stock vesting (in shares)	116,701		3,899
Restricted stock vesting			$ (88)				(88)
Acquisition of consolidated joint venture						(12,037)	(12,037)
Issuance of noncontrolling interests		375				31,010	31,385
Balance (in shares)	17,675,356
Balance at Dec. 31, 2018	$ 204	$ 415,372	$ (91)	$ 126,834	$ (16,788)	$ 29,404	$ 554,935
Balance (in shares)	20,439,208		4,007

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities:
Net Loss	$ (82,052)	$ (38,540)	$ (133,150)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	72,246	62,779	58,069
Deferred financing cost amortization	2,018
Amortization of deferred gains against charter expense	(8,037)	(8,118)	(8,199)
Debt discount and issue cost amortization, net	5,348	6,792	7,397
Director share awards	893	681
Restricted stock amortization	3,494	726
Restricted stock vesting	(88)
Bad debt (recoveries) expense	(880)	(1,283)	4,280
Losses on asset dispositions and impairments, net	8,747	23,547	116,222
Gain from other sales	(428)
Marketable security (gains) losses, net		(10,931)	45
Purchases of marketable securities			(22,997)
Proceeds from sale of marketable securities		51,877	9,169
Derivative (gains), net	(2,854)	(20,256)	(2,995)
Cash settlements on derivative transactions, net	1,372	(512)	(1,432)
Foreign currency losses, net	1,447	1,709	3,312
Deferred income tax benefit	(22,737)	(61,006)	(48,048)
Other, net			1,484
Equity in (earnings) losses of 50% or less owned companies, net of tax	3,415	(4,077)	6,314
Dividends received from 50% or less owned companies	1,724	2,642	777
Changes in operating assets and liabilities:
(Increase) decrease in receivables	(18,980)	28,937	5,637
Decrease (increase) in prepaid expenses and other assets	1,177	6,230	(18,086)
Decrease in accounts payable, accrued expenses and other liabilities	(18,850)	(6,458)	(6,985)
Net cash (used in) provided by operating activities	(53,025)	34,739	(29,186)
Cash Flows from Investing Activities:
Purchases of property and equipment	(51,980)	(69,021)	(100,884)
Cash settlements on derivative transactions, net		(369)	(373)
Proceeds from disposition of property and equipment	22,860	10,843	41,919
Sale of subsidiary to joint venture	8,017
Investments in and advances to 50% or less owned companies	(43,725)	(5,469)	(16,863)
Return of investments and advances from 50% or less owned companies		7,513
Capital distributions from equity investees	16,263	40
Payments received on third-party leases and notes receivable, net			124
Net decrease in construction reserve funds	17,300	32,848	60,406
Principal payments on notes due from equity investees	116
Cash assumed on consolidation of 50% or less owned companies		1,943
Business acquisitions, net of cash acquired		(9,751)
Net cash used in investing activities	(31,149)	(31,423)	(15,671)
Cash Flows from Financing Activities:
Payments on long-term debt	(49,405)	(11,926)	(27,152)
Proceeds from issuance of long-term debt, net of issue costs	62,017	6,545	42,947
Proceeds from exercise of stock options and warrants	833
Distribution of SEACOR Marine restricted stock to Company personnel by SEACOR Holdings		(2,656)
Issuance of stock	42,996
Issuance of warrants	12,809
Purchase of subsidiary shares from noncontrolling interests		(3,693)
Distributions to noncontrolling interests			(205)
Net cash provided by (used in) financing activities	69,250	(11,730)	15,590
Effects of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	(775)	2,194	(2,479)
Net (Decrease) in Cash, Cash Equivalents and Restricted Cash	(15,699)	(6,220)	(31,746)
Cash, Cash Equivalents and Restricted Cash, Beginning of Year	112,551	118,771	150,517
Cash, Cash Equivalents and Restricted Cash, End of Year	$ 96,852	$ 112,551	$ 118,771

Note 1 - Nature of Operations a

Note 1 - Nature of Operations and Accounting Policies	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Basis of Accounting [Text Block]	1. NATURE OF OPERATIONS AND ACCOUNTING POLICIES Nature of Operations and Segmentation. Accounting standards require public business enterprises to report information about each of their operating business segments that exceed certain quantitative thresholds or meet certain other reporting requirements. Operating business segments have been defined as a component of an enterprise about which separate financial information is available and is evaluated regularly by the chief operating decision maker in assessing performance. The Company has identified the following five United States, primarily Gulf of Mexico. Africa, primarily West Africa. Middle East and Asia. Brazil, Mexico, Central and South America. December 31, 2018, 34 seven 27 49% 49% Europe, primarily North Sea. 1991 40 36 four The Spin-off. June 1, 2017, May 22, 2017 ( two Basis of Consolidation. 50% Noncontrolling interests in consolidated subsidiaries are included in the consolidated balance sheets as a separate component of equity. The Company reports consolidated net income (loss) inclusive of both the Company's and the noncontrolling interests' share, as well as the amounts of consolidated net income (loss) attributable to each of the Company and the noncontrolling interests. If a subsidiary is deconsolidated upon a change in control, any retained noncontrolled equity investment in the former controlled subsidiary is measured at fair value and a gain or loss is recognized in net income (loss) based on such fair value. If a subsidiary is consolidated upon a change in control, any previous noncontrolled equity investment in the subsidiary is measured at fair value and a gain or loss is recognized in net income (loss) based on such fair value. The Company employs the equity method of accounting for investments in 50% not 20% 50% may 20%. may 50% may not may 50% may 50% 50% 50% The Company employs the cost method of accounting for investments in 50% not Use of Estimates. may Revenue Recognition. The Company contracts with various customers to carry out management services for vessels as agents for and on behalf of ship owners. These services include crew management, technical management, commercial management, insurance arrangements, sale and purchase of vessels, provisions and bunkering. As the manager of the vessels, the Company undertakes to use its best endeavors to provide the agreed management services as agents for and on behalf of the owners in accordance with sound ship management practice and to protect and promote the interest of the owners in all matters relating to the provision of services hereunder. The Company also contracts with various customers to carry out management services regarding engineering for vessel construction and vessel conversions. The vast majority of the ship management agreements span over the length of one three 18 Revenue that does not December 31 201 8 201 7 201 6 Balance at beginning of year $ 10,104 $ 6,953 $ 6,953 Revenues deferred during the year 3,600 4,699 — Revenues recognized during the year (12,377 ) (1,548 ) — Balance at end of year $ 1,327 $ 10,104 $ 6,953 As of December 31, 2018, of $6.8 August 17, 2012, 11 December 31, 2018 Also, as of December 31, 2018, $1.3 not 606, no The Company earns revenue primarily from the time charter and bareboat charter of vessels to customers. Since the Company charges customers based upon daily rates of hire, vessel revenues are recognized on a daily basis throughout the contract period. Under a time charter, the Company provides a vessel to a customer and is responsible for all operating expenses, typically excluding fuel. Under a bareboat charter, the Company provides a vessel to a customer and the customer assumes responsibility for all operating expenses and assumes all risks of operation. In the U.S. Gulf of Mexico, time charter durations and rates are typically established in the context of master service agreements that govern the terms and conditions of the charter. From time to time, the Company may Contract or charter durations may not two may Cash Equivalents. three Restricted Cash. For the year ended December 31, 2018 2017 2016 Cash $ 95,195 $ 110,234 $ 117,309 Cash equivalents — — — Restricted cash 1,657 2,317 1,462 Total $ 96,852 $ 112,551 $ 118,771 Marketable Securities. Trade and Other Receivables. may Derivative Instruments. not 50% 50% Concentrations of Credit Risk. not not not Inventories. first first December 31, 2018, $0.2 no December 31, 2017 2016. Property and Equipment. not may As of December 31, 2018, Offshore Support Vessels: Crew transfer vessels 10 All other offshore support vessels (excluding crew transfer) 20 The Company's property and equipment as of December 31 Historical Cost (1) Accumulated Depreciation Net Book Value 201 8 Offshore support vessels: AHTS $ 197,343 $ (168,731 ) $ 28,612 FSV (2) 404,310 (98,580 ) 305,730 Supply 64,284 (37,202 ) 27,082 Standby safety 123,731 (97,951 ) 25,780 Specialty 25,683 (20,433 ) 5,250 Liftboats 329,473 (71,887 ) 257,586 Crew transfer 73,589 (46,614 ) 26,975 General machinery and spares 8,457 (8,390 ) 67 Other (3) 15,863 (11,484 ) 4,379 $ 1,242,733 $ (561,272 ) $ 681,461 2017 Offshore support vessels: AHTS $ 198,222 $ (174,159 ) $ 24,063 FSV (2) 424,865 (89,980 ) 334,885 Supply 105,360 (51,494 ) 53,866 Standby safety 118,414 (97,603 ) 20,811 Specialty 30,529 (19,304 ) 11,225 Liftboats 196,504 (54,161 ) 142,343 Crew transfer 65,976 (40,358 ) 25,618 General machinery and spares 14,385 (13,244 ) 1,141 Other (3) 25,581 (19,857 ) 5,724 $ 1,179,836 $ (560,160 ) $ 619,676 ( 1 Includes property and equipment acquired in business acquisitions at acquisition date fair value, and net of the impact of recognized impairment charges. ( 2 Fast support vessels ("FSVs"). ( 3 Includes land, buildings, leasehold improvements, vehicles and other property and equipment. Depreciation and amortization expense totaled $72.2 $62.8 $58.0 2018, 2017 2016, Equipment maintenance and repair costs and the costs of routine overhauls, drydockings and inspections performed on vessels and equipment are charged to operating expense as incurred. Expenditures that extend the useful life or improve the marketing and commercial characteristics of vessels, as well as major renewals and improvements to other properties, are capitalized. Certain interest costs incurred during the construction of vessels are capitalized as part of the vessels' carrying values and are amortized over such vessels' estimated useful lives. Capitalized interest totaled $2.4 $3.6 $7.0 2018, 2017 2016, Intangible Assets. December 31, 2016, Impairment of Long-Lived Assets 2016, $0.1 Impairment of Long-Lived Assets. may not As a result of the difficult conditions experienced in the offshore oil and natural gas markets beginning in the second 2014 During the year ended December 31, 2018, $14.6 four three one December 31, 2017, $27.5 one not one two December 31, 2016, $119.7 one vessels (see Note 10 three The Company's other vessel classes and other individual vessels in active service and cold-stacked status, for which no For vessel classes and individual vessels with indicators of impairment but not December 31, 2018, may Impairment of 50% 50% may December 31, 2018, 2017 2016, $1.2 $8.8 $6.9 50% 4 Business Combinations. 100% 2 Debt Discount and Issue Costs . Self-insurance Liabilities . may Income Taxes . not not The Global Intangible Low Taxed Income ("GILTI") regime effectively imposes a minimum tax on worldwide foreign earnings and subjects U.S. shareholders of controlled foreign corporations ("CFCs") to current taxation on certain income earned through a CFC. The Company has made the policy election to record any liability, associated with GILTI in the period in which it is incurred. Prior to the Spin-off, SEACOR Marine was included in the consolidated U.S. federal income tax return of SEACOR Holdings. SEACOR Holdings' policy for allocation of U.S. federal income taxes required its domestic subsidiaries included in the consolidated U.S. federal income tax return to compute their provision for U.S. federal income taxes on a separate company basis and settle with SEACOR Holdings. In the normal course of business, the Company or SEACOR Holdings may may not not not Deferred Gains - Vessel Sale-Leaseback Transactions and Financed Vessel Sales . third 50% not 6 not December 31 2018 2017 2016 Balance at beginning of year $ 23,553 $ 32,035 $ 40,234 Amortization of deferred gains included in operating expenses as reduction to rental expense (8,037 ) (8,118 ) (8,199 ) Recognition of deferred gains included in losses on asset dispositions and impairments, net (4,490 ) — — Other — (364 ) — Balance at end of year $ 11,026 $ 23,553 $ 32,035 Deferred Gains - Vessel Sales to the Company's 50% 50% 50% 50% 50% December 31 201 8 2017 2016 Balance at beginning of year $ 1,453 $ 1,875 $ 3,064 Amortization of deferred gains included in losses on asset dispositions and impairments, net (25 ) — (36 ) Other (635 ) (422 ) (1,153 ) Balance at end of year $ 793 $ 1,453 $ 1,875 Foreign Currency Translation. Foreign Currency Transactions. Accumulated Other Comprehensive Loss. SEACOR Marine Holdings Inc. Stockholders' Equity Noncontrolling Interests Foreign Currency Translation Adjustments Derivative Gains (Losses) on Cash Flow Hedges, net Total Foreign Currency Translation Adjustments Derivative Gains (Losses) on Cash Flow Hedges, net Other Comprehensive Loss Year Ended December 31, 2015 $ (5,985 ) $ (110 ) $ (6,095 ) $ (529 ) $ — Other comprehensive (loss) income (8,351 ) 286 (8,065 ) (1,085 ) (17 ) $ (9,167 ) Income tax benefit (expense) 2,923 (100 ) 2,823 — — 2,823 Year Ended December 31, 2016 (11,413 ) 76 (11,337 ) (1,614 ) (17 ) $ (6,344 ) Other comprehensive income 4,397 703 5,100 257 18 $ 5,375 Income tax (expense) (1) (6,179 ) (77 ) (6,256 ) — — (6,256 ) Year Ended December 31, 2017 (13,195 ) 702 (12,493 ) (1,357 ) 1 $ (881 ) Other comprehensive loss (2,277 ) (1,972 ) (4,249 ) (88 ) (12 ) $ (4,349 ) Income tax expense — (46 ) (46 ) — — (46 ) Year Ended December 31, 2018 $ (15,472 ) $ (1,316 ) $ (16,788 ) $ (1,445 ) $ (11 ) $ (4,395 ) ( 1 For the year ended December 31, 2017, $4.5 December 22, 2017. Loss Per Share. Basi December 31, 2018, 2017 2016, 2,183,708 4,070,500 4,070,500 December 31, 2018 2017, 192,346 121,693 805,566 613,700 New Accounting Pronouncements. On May 28, 2014, 2014 09, "Revenue from Contracts with Customers (Topic 606 January 1, 2018 not not On February 25, 2016, January 1, 2019 January 1, 2019 $33.9 $32.1 n in lea $1.8 four $8.7 On October 24, 2016, January 1, 2018, $12.1 On Augu st 28, 2018, No. 2018 13, Fair Value Measurement (Topic 820 . This new guidance modifies the disclosure requirements related to fair value measurement. The new guidance is effective for fiscal years beginning after December 15, 2019. not On August 29 2018, No. 2018 15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350 40 December 15, 2019, not

Note 2 - Business Acquisitions

Note 2 - Business Acquisitions	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	2. BUSINESS ACQUISITIONS Falcon Global Holdings February 8, 2018, 72% two 15 six $112.5 $43.3 $18.8 no Sea-Cat Crewzer April 28, 2017, 100% two 50% $4.4 4 no Sea-Cat Crewzer II April 28, 2017, 100% two 50% $11.3 4 no Purchase Price Allocation. December 31 2018 2 Trade and other receivables $ — $ 235 Other current assets 211 4,148 Investments, at Equity, and Advances to 50% or Less Owned Companies — (15,700 ) Property and Equipment 140,257 61,626 Accounts payable — 747 Other current liabilities — (76 ) Long-Term Debt (106,640 ) (41,186 ) Other — (43 ) Minority Interest (18,828 ) — Purchase price (1) $ 15,000 $ 9,751 ( 1 Purchase price in 2018 Purchase price in 2017 $5.9

Note 3 - Equipment Acquisitions

Note 3 - Equipment Acquisitions and Dispositions	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Property, Plant and Equipment Disclosure [Text Block]	3. EQUIPMENT ACQUISITIONS AND DISPOSITIONS Equipment Additions. T $52.0 $69.4 $101.3 2018, 2017 2016, December 31 2018 (1) 2017 2016 FSV — 6 12 Supply — 5 2 Specialty — — 1 Liftboat 6 — — Crew transfer 2 — 2 8 11 17 ( 1 Excludes two 88 888, one Equipment Dispositions. December 31, 2018, $18.6 $18.5 $0.1 $5.9 $4.4 During the year ended December 31, 2017, $11.2 $3.9 $0.1 During the year ended December 31, 2016, $41.4 $3.5 $0.5 Major equipment dispositions for the years ended December 31 2018 (1) 2017 2016 AHTS 1 — — FSV 9 — — Standby safety 3 1 4 Supply — 1 5 Crew transfer 1 — — Liftboats 2 2 — 16 4 9 ( 1 Excludes the sale of (i) a 51% one one three one one one

Note 4 - Investments, at Equity

Note 4 - Investments, at Equity, and Advances to 50% or Less Owned Companies	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Equity Method Investments and Joint Ventures Disclosure [Text Block]	4. INVESTMENTS, AT EQUITY, AND ADVANCES TO 50% Investments, at equity, and advances to 50% December 31 Ownership 2018 2017 MexMar 49.0% $ 53,840 $ 60,980 SEACOSCO 50.0% 28,002 — OSV Partners 30.4% 11,087 10,006 SEACOR Marlin 49.0% 7,579 — MEXMAR Offshore International 49.0% 4,900 — Offshore Vessel Holdings 49.0% 4,900 — Dynamic Offshore Drilling 19.0% 2,263 4,958 Nautical Power 50.0% — 6,408 Other 20.0% — 50.0% 9,202 9,817 $ 121,773 $ 92,169 Condensed Financial Information of MexMar. December 31 2018 2017 Current assets $ 38,113 $ 71,990 Noncurrent assets 215,207 194,990 Current liabilities 27,610 23,931 Noncurrent liabilities 115,948 147,043 2018 2 017 2016 Operating Revenues $ 57,003 $ 67,003 $ 70,521 Costs and Expenses: Operating and administrative 25,932 29,405 37,613 Depreciation 16,295 15,977 13,958 42,227 45,382 51,571 Operating Income $ 14,776 $ 21,621 $ 18,950 Net Income $ 5,584 $ 9,233 $ 6,476 Condensed Financial Information of Falcon Global, Sea-Cat Crewzer and Sea-Cat Crewzer II. December 31 201 7 (1) 201 6 Operating Revenues $ 5,075 $ 21,611 Costs and Expenses: Operating and administrative 3,752 12,837 Depreciation 2,324 3,694 6,076 16,531 Operating (Loss) Income $ (1,001 ) $ 5,080 Net (Loss) Income $ (2,699 ) $ 778 ( 1 Includes 2017 No 2018 2017. Combined Condensed Financial Information of Other Investees (excluding MexMar, Falcon Global, Sea-Cat Crewzer and Sea-Cat Crewzer II). December 31 2018 2017 Current assets $ 61,287 $ 61,360 Noncurrent assets 352,421 247,038 Current liabilities 32,302 14,603 Noncurrent liabilities 209,752 138,789 2018 2017 2016 Operating Revenues $ 54,853 $ 77,409 $ 77,571 Costs and Expenses: Operating and administrative 53,967 46,748 51,136 Depreciation 10,148 12,198 13,181 64,115 58,946 64,317 Loss on Asset Dispositions and Impairments, Net (89 ) — (21,323 ) Operating (Loss) Income $ (9,351 ) $ 18,463 $ (8,069 ) Net (Loss) Income $ (20,383 ) $ 6,451 $ (19,229 ) As of December 31, 2018 2017, 50% $28.5 $46.1 MexMar. MexMar owns and operates 16 December 31, 2018, $9.8 two December 31, 2017, $7.4 December 31, 2016, $7.4 two $34.0 December 31, 2018, 2017 2016, $0.3 $0.3 $0.3 December 31, 2016, $5.1 SEACOSCO. On January 17, 2018, eight $163.3 70% two March 31, 2018, five June 30, 2018, one 2019. six six 18 50% December 31, 2018, $29.6 $2.0 first 2019. one five OSV Partners. SEA five December 31, 2017 September 28, 2018, September 28, 2021, $5.0 $5.0 $1.1 $1.1 September 30, 2020) $2.1 no not December 31, 2017, $6.0 $2.3 December 31, 2016, $1.2 December 31, 2018, 2017 2016, $0.6 $0.6 $0.5 SEACOR Marlin. September 13, 2018, 51% $8.0 $0.4 MexMar Offshore International. December 20, 2018, 49% 51% 14 12 two 11 two one two $10.0 Offshore Vessel Holdings. December 28, 2018, $4.9 49% Dynamic Offshore Drilling. Dynamic Offshore Drilling Ltd. ("Dynamic Offshore Drilling") was established to construct and operate a jack-up drilling rig that was delivered in the first 2013. December 31, 2017, $8.3 December 31, 2018, $2.7 $2.3 not N au In the quarter ending September 30, 2018, $6.4 Falcon Global. Falcon Global was formed to construct and operate two three March 31, 2017, $0.4 $2.0 March 2017, 100% March 31, 2017 Cash $ 1,943 Marketable securities 785 Trade and other receivables (291 ) Investments, at Equity, and Advances to 50% or Less Owned Companies (19,374 ) Property and Equipment 96,000 Accounts payable 3,201 Other current liabilities 1,153 Long-Term Debt 58,335 Other Liabilities (1,000 ) Noncontrolling interests in subsidiaries 17,374 Sea-Cat Crewzer II. Sea-Cat Crewzer II owns and operates two April 28, 2017, 100% 50% $11.3 2 Sea-Cat Crewzer. Sea-Cat Crewzer owns and operates two April 28, 2017, 100% 50% $4.4 2 Other. The Co 50% erate eight December 31, 2018, $1.7 50% December 31, 2018, $1.2 50% December 31, 2017, $2.6 $0.8 $0.2 50% December 31, 2017, $0.5 50% December 31, 2016, $0.8 50% $0.5 50% December 31, 2016, $0.5 50% $2.7 50% December 31, 2018, 2017 2016, ed $0.3 $0 .7 $0.8 50% Two of the Company's 50% first $0.8 December 31, 2018. The Company guarantees certain of the outstanding charter receivables of one 50% December 31, 2018, $0.3

Note 5 - Construction Reserve F

Note 5 - Construction Reserve Funds	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Restricted Assets Disclosure [Text Block]	5. CONSTRUCTION RESERVE FUNDS The Company has established, pursuant to Section 511 1936, three two one As of December 31, 2018, 2017 2016, December 31 2018 2017 2016 Withdrawals $ (17,300 ) $ (39,163 ) $ (87,820 ) Deposits — 6,315 27,414 $ (17,300 ) $ (32,848 ) $ (60,406 )

Note 6 - Leases

Note 6 - Leases	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Lessee, Operating Leases [Text Block]	6. LEASES As of December 31, 2018, eight first one three 1 Total rental expense for the Company's operating leases for the years ended December 31, 2018, 2017 2016 $13.3 $14.5 $19.4 December 31 one December 31, 2018 2019 $ 14,288 2020 13,826 2021 6,480 2022 331 2023 and beyond 661 The Company performed an impairment analysis and determined that some of the leased offshore support vessels are impaired due to an operating or cash flow loss currently and in the forecasted future. The Company recorded impairment losses of $6.8 three December 31, 2018 $5.4 one December 31, 2017. On February 25, 2016, January 1, 2019 January 1, 2019 addition of $33.9 $32.1 $1.8 four $8.7

Note 7 - Long-term Debt

Note 7 - Long-term Debt	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Long-term Debt [Text Block]	7. LONG-TERM DEBT The Company's long-term debt obligations as of December 31 2018 2017 SEACOR Marine Foreign Holdings Syndicated Credit Facility $ 126,750 $ — Convertible Senior Notes 125,000 175,000 Falcon Global USA Term Loan Facility 109,099 — Sea-Cat Crewzer III Term Loan Facility 25,989 29,078 Windcat Workboats Facilities 24,850 25,202 Falcon Global USA Revolver 15,000 — SEACOR 88/888 Term Loan 11,000 — BNDES Equipment Construction Finance Notes 5,284 7,234 Falcon Global International Term Loan Facility — 54,870 Sea-Cat Crewzer II Term Loan Facility — 20,871 Sea-Cat Crewzer Term Loan Facility — 18,504 C-Lift Acquisition Notes — 16,000 Cypress CKOR Term Loan — 1,300 442,972 348,059 Portion due within one year (16,812 ) (22,858 ) Debt discount (32,005 ) (27,373 ) Issue costs (6,301 ) (5,787 ) $ 387,854 $ 292,041 The Company's contractual long-term debt maturities for the years ended December 31 2019 $ 16,812 2020 25,489 2021 51,381 2022 25,150 2023 222,900 Years subsequent to 2023 101,240 $ 442,972 SEACOR Marine Foreign Holdings September 26, 2018, $130.0 20 2023 6.5625% $101.3 $99.9 $1.4 $30.1 $3.3 December 2018. $0.6 October 2018, $65.0 Convertible Senior Notes. December 1, 2015, $175.0 3.75%, December 1, 2022, 23.26 $1,000 $0.01 Upon completion of the Spin-off, the Company bifurcated the embedded conversion option liability of $27.3 9 10 7.95% On May 2, 2018, $50 1,886,792 $0.01 37.73 $1,000 $26.50 25 May 2, 2018. $125.0 3.75% 4.25% 12 December 1, 2023. June 15 December 15 Falcon Global USA. February 8, 2018, January 18, 2018, 11 February 8, 2018, $15.0 $131.1 $116.1 $15.0 7.0625% 2024 15 two $10.0 2020. December 31, 2018, $15.0 $7.0 two 72% Sea-Cat Crewzer III Term Loan Facility. April 21, 2016, €27.6 2.76%. December 31, 2017 2016, $7.1 $22.8 $2.7 2016 December 31, 2018 2017, $3.1 $0.6 Windcat Workboats Facilities. May 24, 2016, €25.0 38 3.00% 3.30% 2021. 1.20% 1.32% December 31, 2016, $23.5 €21.0 $22.9 $0.6 During the year ended December 31, 2018, €6.0 $7.5 $8.5 $1.0 SEACOR 88/888. July 5, 2018, $11.0 two not 2023, 5.9375% two not x $5.5 50% October 2018, $5.5 BNDES Equipment Construction Finance Notes. two first 4.00% July October 2021. December 31, 2018, 2017 2016, $2.0 $2.0 $2.0 Falcon Global International Term Loan Facility. August 3, 2015, two two $62.5 $18.0 five June 30, 2022. November 3, 2017, $0.2 In March 2017, 100% $58.3 $1.0 March 31, 2017 4 April 2017, nine December 31, 2017, $4.4 During the year ended December 31, 2018, $3.0 $51.9 September 28, 2018. Sea-Cat Crewzer II Term Loan Facility. April 28, 2017, 100% 50% 2 4 2019 first December 19, 2017, $0.1 $17.3 1.52%, 2.10% 2.75% 5.64% December 31, 2017 December 31, 2017, $1.2 During the year ended December 31, 2018, $1.8 $19.1 September 28, 2018. Sea-Cat Crewzer Term Loan Facility. April 28, 2017, 100% 50% 2 4 2019 first December 19, 2017, $0.1 $15.3 1.52%, 2.10% 2.75% 5.64% December 31, 2017 December 31, 2017, $1.1 During the year ended December 31, 2018, $1.6 $16.9 September 28, 2018. C-Lift Acquisition Notes. 50% first two December 13, 2017, $0.1 December 2019. December 31, 2017 2016, $1.5 $1.7 During the year ended December 31, 2018, $4.0 $12.0 September 28, 2018 Cypress CKOR Term Loan. December 12, 2016, 100% one one $3.1 2 December 31, 2017 2016, $1.2 $0.6 December 31, 2018, $1.3 Letters of Credit. December 31, 2018, $2.8 one

Note 8 - Income Taxes

Note 8 - Income Taxes	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Income Tax Disclosure [Text Block]	8. INCOME TAXES On December 22, 2017, 66Act 2018 • reduced U.S. Federal Corporate Income Tax Rate from 35% 21%; • created a new provision to tax the income of foreign subsidiaries referred to as GILTI; • generally eliminated U.S. Federal tax on dividends from foreign subsidiaries; • created a limitation on deductible interest expense (Sec 163 • established new limitations on the deductibility on compensation for Covered Employees (Sec 162 • changed rules regarding utilization and the carryforward period of Net Operating Losses (“NOL’s”) generated after December 31, 2017. In arriving at the 2018 The GILTI regime effectively imposes a minimum tax on worldwide foreign earnings and subjects U.S. shareholders of controlled foreign corporations ("CFC's) to current taxation on certain income earned through a CFC. For the period ending December 31, 2018, not Loss before income tax benefit and equity in earnings (losses) of 50% December 31 2018 2017 2016 United States $ (72,540 ) $ (90,696 ) $ (169,523 ) Foreign (28,226 ) (45,112 ) (28,095 ) Eliminations 8,782 18,785 7,313 $ (91,984 ) $ (117,023 ) $ (190,305 ) The components of income tax expense (benefit) for the years ended December 31 201 8 201 7 201 6 Current: Federal $ 5,987 $ (16,705 ) $ (20,718 ) State 3 (42 ) (139 ) Foreign 3,400 3,347 5,436 9,390 (13,400 ) (15,421 ) Deferred: Federal (21,466 ) (60,750 ) (47,692 ) State (1,404 ) (172 ) (446 ) Foreign 133 (84 ) 90 (22,737 ) (61,006 ) (48,048 ) $ (13,347 ) $ (74,406 ) $ (63,469 ) As of December 31, 2017, $3.9 $3.9 December 31, 2018, During the preparation of the 2017 2017 $3.4 2017 December 31, 2018. For 2018, $1.4 50% The following table reconciles the difference between the statutory federal income tax rate for the Company and the effective income tax rate for the years ended December 31: 2018 2017 2016 Statutory rate (21.0 )% (35.0 )% (35.0 )% U.S. federal income tax law changes — % (37.3 )% — % SEACOR Holdings share awards to Company personnel 0.2 % 2.3 % 0.4 % Non-deductible expenses — % 1.8 % 0.1 % Exclusion of foreign subsidiaries with accumulated losses and withholding tax 9.3 % 2.7 % 1.1 % Noncontrolling interests (1.5 )% 1.7 % 0.2 % State taxes (1.5 )% (0.2 )% (0.3 )% Other 0.0 % 0.4 % 0.1 % (14.5 )% (63.6 )% (33.4 )% For the year ending December 31, 2018, 14.5% 21% no For the year ending December 31, 2017, 63.6% 35% $43.7 35% 21% The components of net deferred income tax liabilities as of December 31 2018 2017 Deferred tax liabilities: Property and equipment $ 65,880 $ 55,262 Investments in 50% or Less Owned Companies 3,040 4,258 Other 7,789 5,901 Total deferred tax liabilities 76,709 65,421 Deferred tax assets: Federal Net Operating Loss Carryforwards 20,974 5,111 Other 11,677 5,373 32,651 10,484 Valuation Allowance (624 ) (569 ) Total deferred tax assets 32,027 9,915 Net deferred tax liabilities $ 44,682 $ 55,506 As discussed above, the Section 163 thirty December 31, 2018, $7.3 30% December 31, 2017 eighty December 31, 2018, $42.2 December 31, 2017 $57.6 2017 may 20 2037 2018 no 80 As of December 31, 2018 2017, $0.6

Note 9 - Derivative Instruments

Note 9 - Derivative Instruments and Hedging Strategies	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Derivative Instruments and Hedging Activities Disclosure [Text Block]	9. DERIVATIVE INSTRUMENTS AND HEDGING STRATEGIES Derivative instruments are classified as either assets or liabilities based on their individual fair values. The fair values of the Company's derivative instruments as of December 31 Balance Sheet 2018 2017 Classification Derivative Asset Derivative Liability Derivative Asset Derivative Liability Derivatives designated as hedging instruments: Interest rate swap agreements (cash flow hedges) Current $ — $ 1,659 $ 260 $ 20 — 1,659 260 20 Derivatives not designated as hedging instruments: Conversion option liability on Convertible Senior Notes Long-Term — 5,276 — 6,832 Interest rate swap agreements Current — — 159 46 $ — $ 6,935 $ 419 $ 6,898 _________________ Fair Value Hedges. may may December 31, 2017, $0.1 December 31, 2016, $0.8 Cash Flow Hedges. 50% 50% $1.6 December 31, 2018, $0.2 December 31, 2017 $2.5 December 31, 2016 December 31, 2018, 50% • Windcat Workboats had two 2021 0.03% €15.0 $17.2 • SEACOR Marine Foreign Holdings had an interest rate swap agreement maturing in 2023 3.32% $9.8 • SEACOR Marine Foreign Holdings had an interest rate swap agreement maturing in 2023 3.195% $54.1 • SEACOR 88/888 2023 88/888 3.5% $5.5 • MexMar had five 2023 1.71% 2.10% $97.0 Derivative Instruments. not If a derivative qualifies for hedge accounting and is designated as a cash flow hedge, the effective portion of the change in fair value of the derivative is deferred in Accumulated Other Comprehensive Income (“AOCI”), a component of owners’ equity, and reclassified to earnings when the forecasted transaction occurs. Cash flows from a derivative instrument designated as a hedge are classified in the same category as the cash flows from the item being hedged. As such, we include the cash flows from interest rate derivative instruments in interest expense. If a derivative does not not We formally document all relationships between hedging instruments and hedged items, as well as its risk management objectives and strategy for undertaking the hedge. This documentation includes the specific identification of the hedging instrument and the hedged item, the nature of the risk being hedged and the manner in which the hedging instrument’s effectiveness will be assessed. At the inception of the hedge, and on an ongoing basis, we assess whether the derivatives used in hedging transactions are highly effective in offsetting changes in cash flows of hedged items. The relationship between the hedging instrument and the hedged item must be highly effective in achieving the offset of changes in cash flows attributable to the hedged risk both at the inception of the contract and on an ongoing basis. We measure hedge ineffectiveness on a quarterly basis and reclassify any ineffective portion of the gain or loss related to the change in fair value to earnings in the current period. We will discontinue hedge accounting on a prospective basis when a hedge instrument is terminated or ceases to be highly effective. Gains and losses deferred in AOCI related to cash flow hedges for which hedge accounting has been discontinued remain deferred until the forecasted transaction occurs. If it is no For balance sheet classification purposes, we analyze the fair values of the derivative instruments on a contract by contract basis and report the related fair values and any related collateral by counterparty on a gross basis. Realized and unrealized gains and losses on derivatives designated as cash flow hedges that are entered into by the Company’s 50% 50% The fair value of our derivative instruments, depending on the type of instrument, was determined by the use of present value methods or standard option valuation models with assumptions about commodity prices based on those observed in underlying markets. The estimated fair value of our derivative instruments was a net liability of $6.9 December 31, 2018. The following tables reflect amounts recorded in Other Comprehensive Income (“OCI”) and amounts reclassified from OCI to revenue and expense for the periods indicated: Gain (Loss) Recognized in OCI on Derivatives (Effective Portion) Derivatives in Cash Flow Hedging Relationships 2018 2017 2016 Interest rate swap contracts $ (1,939 ) $ 214 $ (2,493 ) Joint venture interest rate swap contracts (76 ) 389 2,744 Gain (Loss) Reclassified from OCI into Income (Effective Portion) Location of Gain 2018 2017 2016 Interest expense $ 31 118 18 Our consolidated earnings are also affected by the use of the mark-to-market method of accounting for derivative instruments that do not not Other Derivative Instruments. not December 31 Derivative gains (losses), net 201 8 201 7 201 6 Conversion option liability on Convertible Senior Notes $ 1,556 $ 20,422 $ — Interest rate swap agreements 1,298 46 (18 ) Options on equities — — 3,095 Forward currency exchange, option and future contracts — (212 ) (82 ) $ 2,855 $ 20,256 $ 2,995 The conversion option liability relates to the bifurcated embedded conversion option in the Convertible Senior Notes (See Notes 7 10 The Company and certain of the Company's 50% December 31, 2018, 50% • OSV Partners had two 2020 1.89% 2.27% $27.9 Prior to 2017, The Company enters and settles forward currency exchange, option and future contracts with respect to various foreign currencies. These contracts enable the Company to buy currencies in the future at fixed exchange rates, which could offset possible consequences of changes in currency exchange rates with respect to the Company's business conducted outside of the United States. The Company generally does not twelve eighteen no December 31, 2018.

Note 10 - Fair Value Measuremen

Note 10 - Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Fair Value Disclosures [Text Block]	10. FAIR VALUE MEASUREMENTS The fair value of an asset or liability is the price that would be received to sell an asset or transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The Company utilizes a fair value hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs when measuring fair value and defines three may Level 1 Level 2 Level 1 not Level 3 no The Company's financial assets and liabilities as of December 31 Level 1 Level 2 Level 3 (1) 2018 ASSETS Construction reserve funds $ 28,221 $ — $ — LIABILITIES Derivative instruments (included in other current liabilities) — 1,659 — Conversion Option Liability on Convertible Senior Notes — — 5,276 2017 ASSETS Derivative instruments (included in other receivables) $ — $ 419 $ — Construction reserve funds 45,361 — — LIABILITIES Derivative instruments (included in other current liabilities) — 66 — Conversion Option Liability on Convertible Senior Notes — — 6,832 ( 1 For the year ended December 31, 2018, $1.6 third Level 3 Level 3 The estimated fair value of the Company's other financial assets and liabilities as of December 31 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 201 8 ASSETS Cash, cash equivalents and restricted cash $ 96,852 $ 96,852 $ — $ — Investments, at cost, in 50% or less owned companies (included in other assets) see below LIABILITIES Long-term debt, including current portion 404,666 — 388,949 — 201 7 ASSETS Cash, cash equivalents and restricted cash $ 112,551 $ 112,551 $ — $ — Investments, at cost, in 50% or less owned companies (included in other assets) 132 see below LIABILITIES Long-term debt, including current portion 314,899 — 291,932 — The carrying value of cash, cash equivalents and restricted cash approximates fair value. The fair value of the Company's long-term debt was estimated by using discounted cash flow analysis based on estimated current rates for similar types of arrangements. It was not 50% not The Company's non-financial assets and liabilities that were measured at fair value during the years ended December 31 Level 1 Level 2 Level 3 2018 ASSETS Property and equipment: AHTS $ — $ 2,000 $ — Liftboats — — 134,775 Specialty — 4,500 — 2017 ASSETS Property and equipment: AHTS $ — $ 12,400 $ — FSV — 175 — Specialty — 750 — Investments, at equity, in 50% or less owned companies — 20,658 20,430 Property and equipment. December 31, 2018 2017, $14.6 $27.5 1 Level 2 Level 3 third 2014. The significant unobservable inputs used in the fair value measurement for the AHTS fleet during 2018 Level 3 two third Level 3 two Investments, at equity, in 50% December 31, 2018, zero 50% December 31, 2017, 50% Level 2 Level 3 third 2017 100% 4

Note 11 - Warrants

Note 11 - Warrants	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Warrants and Rights [Text Block]	11. WARRANTS On April 26, 2018, $56,855,000 2,168,586 674,164 $0.01 April 26, 2018, 25 $0.01 May 2, 2018 $50.0 1,886,292 $0.01 25 May 2, 2018. May 31, 2018 June 8, 2018, 250,693 38,857 2,271,406 December 31, 2018.

Note 12 - Stockholders' Equity

Note 12 - Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Stockholders' Equity Note Disclosure [Text Block]	12. STOCKHOLDERS' EQUITY On January 1, 2018, October 24, 2016, $12.1 On February 8, 2018, 15 six $15.0 $131.1 $9.5 $0.5 $0.4 On March 26, 2018, 103,213 $1.8 4 2 On April 26, 2018, $56.9 4 2 On May 2, 2018, $50.0 4 2 On May 31, 2018 June 8, 2018, 250,693 38,857 108

Note 13 - Noncontrolling Intere

Note 13 - Noncontrolling Interests in Subsidiaries	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Noncontrolling Interest Disclosure [Text Block]	13. NONCONTROLLING INTERESTS IN SUBSIDIARIES Noncontrolling interests in the Company's consolidated subsidiaries as of December 31 Noncontrolling Interests 2018 2017 Falcon Global Holdings 28.0% $ 26,989 $ 12,087 Windcat Workboats 12.5% 2,115 2,608 Other 1.8% 300 280 $ 29,404 $ 14,975 Falcon Global Holdings. February 8, 2018, January 18, 2018, 11 15 six $112.5 $43.3 $18.8 72% During the year ended December 31, 2018, $14.3 $4.0 December 31, 2018, $98.1 Windcat Workboats. December 31, 2017, 12.5% $3.7 December 31, 2018 2017, $16.9 $21.1 December 31, 2018, $3.1 $0.4 December 31, 2017, $2.1 $0.4 December 31, 2016, $4.5 $1.1

Note 14 - Savings and Multi-emp

Note 14 - Savings and Multi-employer Pension Plans	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Pension and Other Postretirement Benefits Disclosure [Text Block]	14. SAVINGS AND MULTI-EMPLOYER PENSION PLANS SEACOR Marine Savings Plan. January 1, 2016, 401 June 1, 2017 January 1, 2019, 1.0% December 31, 2018 2017 not MNOPF and MNRPF. two 2001 1978 Under the direction of a court order, any funding deficit of the MNOPF is to be remedied through funding contributions from all participating current and former employers. Prior to 2015, $19.4 November 7, 2018, £9.0 not December 31, 2018, $1.5 $1.9 The cumulative funding deficits of the MNRPF were being recovered by additional annual contributions from current employers that were subject to adjustment following the results of future tri-annual actuarial valuations. In 2015, $6.9 October 30, 2018 July 20, 2018, second 2018 $1.19 £0.9 first September 2018 October 2018 September 2019 October 2019. December 31, 2018, $0.4 Other Plans. December 31, 2018, 2017 2016, $0.7

Note 15 - Share Based Compensat

Note 15 - Share Based Compensation	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	15. SHARE BASED COMPENSATION Equity Incentive Plan. 2017, 2017 "2017 2017 two 2,174,000 2017 10% 2017 may December 31, 2018, 1,157,924 2017 Restricted stock typically vests from one four one four 2017 no tenth 2017 Distribution of SEACOR Marine Restricted Stock by SEACOR Holdings. 2017 $2.7 120,693 16 Employee Stock Purchase Plan. 2017, 2017 85% first 300,000 ten Share Award Transactions. 2017 December 31: 2018 2017 Director Stock Awards Granted 19,285 3,000 Restricted Stock Activity: Outstanding as of the beginning of year 121,693 — Granted - 2017 Plan 120,600 1,000 Distributed by SEACOR Holdings in connection with the Spin-off — 120,693 Vested 49,947 — Forfeited — — Outstanding as of the end of year 192,346 121,693 Stock Option Activity: Outstanding as of the beginning of year 613,700 — Granted - 2017 Plan 258,491 613,700 Exercised 66,625 — Forfeited — — Expired — — Outstanding as of the end of year 805,566 613,700 During the year ended December 31, 2018, $4.4 2017 December 31, 2018, $6.8 1.7982 1.4542 During the year ended December 31, 2017, $0.8 2017 $0.6 December 31, 2017, $5.2 The weighted average fair value of restricted stock granted under the 2017 $21.63 $12.50 December 31, 2018 2017, 2017 $9.99 $6.42 December 31, 2018 2017, December 31, 2018 2017, no 50.4 52.5, 2.79% 2.22%, 6.00 2018 $0.8 During the year ended December 31, 2018, Restricted Stock Number of Shares Weight Average Grant Price Non-Vested as of December 31, 2017 121,693 $ 24.01 Granted 120,600 12.63 Vested 49,947 24.85 Non-Vested as of December 31, 2018 192,346 22.32 During the year ended December 31, Stock Options Number of Shares Weight Average Grant Price Non-Vested as of December 31, 2017 613,700 $ 12.50 Granted 258,491 19.70 Exercised 66,625 12.50 Non-Vested as of December 31, 2018 805,566 14.81 Exercisable as of December 31, 2018 (1) 261,691 14.02 ( 1 The weighted average remaining contractual term is 8.9849 As of December 31, 2018, 805,566 $14.81 9.0224 December 31, 2018, no

Note 16 - Related Party Transac

Note 16 - Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Related Party Transactions Disclosure [Text Block]	16. RELATED PARTY TRANSACTIONS The Company provided services of $0.1 December 31, 2017 2016. In connection with the Spin-off, SEACOR Marine entered into certain agreements with SEACOR Holdings that govern SEACOR Marine's relationship with SEACOR Holdings following the Spin-off, including a Distribution Agreement, two As of December 31, 2018, $40.6 6 14 December 31, 2017, $69.1 8 6 15 0.5% $0.3 $0.3 $0.4 2018, 2017 2016, Pursuant to one 50% not $6.0 not $3.0 December 31, 2018 2017, $0 $0.7 Immediately preceding the Spin-off and pursuant to an Investment Agreement dated November 30, 2015 $3.4 Following the completion of the Spin-off, the Company is no $6.3 December 31, 2018 2017, $4.5 $3.3 Prior to the Spin-off, certain costs and expenses of the Company were borne by SEACOR Holdings and charged to the Company. These costs and expenses are included in both operating and administrative and general expenses in the accompanying consolidated statements of loss and are summarized as follows for the years ended December 31 ( 2018 2017 2016 Participation in SEACOR Holdings employee benefit plans $ — $ 899 $ 3,702 Participation in SEACOR Holdings share award plans — 8,383 4,588 Shared services allocation for administrative support — 1,932 4,365 $ — $ 11,214 $ 12,655 • SEACOR Holdings maintained self-insured health benefit plans for participating employees, including those of the Company, and charged the Company for its share of total plan costs incurred based on the percentage of its participating employees. Following the Spin-off, the Company no • certain officers and employees of the Company received compensation through participation in SEACOR Holdings' share award plans. The Company paid SEACOR Holdings for the fair value of its employees' share awards. Pursuant to the Employee Matters Agreement with SEACOR Holdings, participating Company personnel vested in all outstanding SEACOR Holdings share awards upon the Spin-off and received SEACOR Marine restricted stock from the Spin-off distribution in connection with outstanding SEACOR Holdings restricted stock held. As a consequence, the Company paid SEACOR Holdings $9.4 $2.7 120,693 15 $6.7 $1.7 • prior to the Spin-off, SEACOR Holdings provided certain administrative support services to the Company under a shared services arrangement, including but not Prior to the Spin-off, SEACOR Holdings incurred various corporate costs in connection with providing certain corporate services, including, but not November 30, 2015, $7.7 December 1, 2015 Charles Fabrikant (Non-Executive Chairman of SEACOR Marine), John Gellert (President, Chief Executive Officer and Director of SEACOR Marine), other members of the Company's management and board of directors and other unaffiliated individuals indirectly invested in OSV Partners by purchasing interests from three 2018, $7.5 $5 second $2.5 December 31, 2018, $1.5 3.9%, $0.3 5.0%, $0.2 3.9%, second $0.1 3.9%, December 31, 2018, $0.3 $0.4 31.7% 30.4% 38.6% 43.0% second 43.0% third On January 25, 2019, 6.25% not one two £1,552,780 $2.0 6.25% not two 100%

Note 17 - Commitments and Conti

Note 17 - Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Commitments and Contingencies Disclosure [Text Block]	17. COMMITMENTS AND CONTINGENCIES As of December 31, 2018, $78.2 four three two three 2019 $ 51,132 2020 27,046 $ 78,178 The Company had indefinitely deferred an additional $20.2 In the normal course of its business, the Company becomes involved in various other litigation matters including, among other things, claims by third not As of December 31, 2018, five first one three 6 The Company has $2.5

Note 18 - Major Customers and S

Note 18 - Major Customers and Segment Information	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Segment Reporting Disclosure [Text Block]	18. MAJOR CUSTOMERS AND SEGMENT INFORMATION During the years ended December 31, 2018, 2017 2016, $26.5 10.3%, $26.8 15.2% $28.4 13.2%, December 31, 2018, 2017 2016, ten 47%, 59%, 58%, one For the years ended December 31, 2018, 2017 2016, 79%, 87%, 85%, 1.3 $1.9 4.2 50% The Company's offshore support vessels are highly mobile and regularly and routinely move between countries within a geographic region of the world. In addition, these vessels may one one not The following tables summarize (in thousands) the operating results and property and equipment of the Company's reportable segments. Direct vessel profit is the Company's measure of segment profitability, a key metric in assessing the performance of its fleet. Direct vessel profit is defined as operating revenues less direct operating expenses excluding leased-in equipment expense. The Company utilizes direct vessel profit as its primary financial measure to analyze and compare the operating performance of its individual vessels, fleet categories, regions and combined fleet. United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Brazil, Mexico, Central and South America Europe (primarily North Sea) Total For the year ended December 31, 2018 Operating Revenues: Time charter $ 38,802 $ 43,847 $ 50,072 $ 17,343 $ 72,188 $ 222,252 Bareboat charter — — — 4,635 — 4,635 Other 14,762 7,661 (887 ) 1,554 3,632 26,722 53,564 51,508 49,185 23,532 75,820 253,609 Direct Costs and Expenses: Operating: Personnel 18,708 16,538 16,806 4,399 38,577 95,028 Repairs and maintenance 5,152 6,330 11,172 1,011 9,614 33,279 Drydocking 1,957 2,085 1,362 128 6,055 11,587 Insurance and loss reserves 2,922 1,096 1,371 495 1,190 7,074 Fuel, lubes and supplies 3,568 3,826 4,027 1,225 4,329 16,975 Other 393 4,313 3,980 1,130 1,332 11,148 32,700 34,188 38,718 8,388 61,097 175,091 Direct Vessel Profit $ 20,864 $ 17,320 $ 10,467 $ 15,144 $ 14,723 78,518 Other Costs and Expenses: Operating: Leased-in equipment $ 7,420 $ 3,843 $ — $ — $ 212 11,475 Administrative and general 52,813 Depreciation and amortization $ 23,227 $ 10,453 $ 18,762 $ 7,908 $ 11,896 72,246 136,534 Losses on Asset Dispositions and Impairments, Net (8,747 ) Operating Loss $ (66,763 ) As of December 31, 2018 Property and Equipment: Historical cost $ 432,336 $ 184,361 $ 306,897 $ 124,177 $ 194,963 $ 1,242,734 Accumulated depreciation (224,737 ) (55,206 ) (81,378 ) (57,002 ) (142,949 ) (561,272 ) $ 207,599 $ 129,155 $ 225,519 $ 67,175 $ 52,014 $ 681,462 Total Assets (1) $ 351,748 $ 140,335 $ 260,002 $ 137,983 $ 59,716 $ 949,784 ( 1 Total assets exclude $153,151 United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Brazil, Mexico, Central and South America Europe (primarily North Sea) Total For the year ended December 31, 2017 Operating Revenues: Time charter $ 18,079 $ 32,866 $ 33,410 $ 2,977 $ 73,213 $ 160,545 Bareboat charter — — — 4,636 — 4,636 Other 4,217 1,080 474 552 2,279 8,602 22,296 33,946 33,884 8,165 75,492 173,783 Direct Costs and Expenses: Operating: Personnel 15,621 13,419 16,883 809 34,768 81,500 Repairs and maintenance 3,594 5,957 9,037 274 8,793 27,655 Drydocking 1,828 2,180 968 — 4,059 9,035 Insurance and loss reserves 3,286 677 1,444 316 801 6,524 Fuel, lubes and supplies 1,485 2,815 3,727 223 3,782 12,032 Other 249 3,319 5,240 117 980 9,905 26,063 28,367 37,299 1,739 53,183 146,651 Direct Vessel Profit (Loss) $ (3,767 ) $ 5,579 $ (3,415 ) $ 6,426 $ 22,309 27,132 Other Costs and Expenses: Operating: Leased-in equipment $ 8,152 $ 3,870 $ 862 $ — $ 64 12,948 Administrative and general 56,217 Depreciation and amortization $ 22,060 $ 9,280 $ 17,724 $ 3,608 $ 10,107 62,779 131,944 Losses on Asset Dispositions and Impairments, Net (23,547 ) Operating Loss $ (128,359 ) As of December 31, 2017 Property and Equipment: Historical cost $ 410,475 $ 192,600 $ 326,378 $ 72,484 $ 177,899 $ 1,179,836 Accumulated depreciation (230,636 ) (57,228 ) (100,435 ) (37,281 ) (134,580 ) (560,160 ) $ 179,839 $ 135,372 $ 225,943 $ 35,203 $ 43,319 $ 619,676 Total Assets (1) $ 310,675 $ 140,173 $ 234,471 $ 103,135 $ 50,704 $ 839,158 ( 1 Total assets exclude $169,346 United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Brazil, Mexico, Central and South America Europe (primarily North Sea) Total For the year ended December 31, 2016 Operating Revenues: Time charter $ 28,902 $ 36,706 $ 41,657 $ 196 $ 78,866 $ 186,327 Bareboat charter — — — 8,833 — 8,833 Other 3,954 856 12,230 1,180 2,256 20,476 32,856 37,562 53,887 10,209 81,122 215,636 Direct Costs and Expenses: Operating: Personnel 22,305 12,628 18,381 2,117 39,713 95,144 Repairs and maintenance 2,721 2,628 6,426 232 9,275 21,282 Drydocking 228 1,098 2,117 — 4,378 7,821 Insurance and loss reserves 3,363 539 731 43 1,006 5,682 Fuel, lubes and supplies 1,392 2,512 4,215 21 3,948 12,088 Other 271 2,519 3,247 114 1,180 7,331 30,280 21,924 35,117 2,527 59,500 149,348 Direct Vessel Profit $ 2,576 $ 15,638 $ 18,770 $ 7,682 $ 21,622 66,288 Other Costs and Expenses: Operating: Leased-in equipment $ 7,975 $ 3,898 $ 4,389 $ 913 $ 402 17,577 Administrative and general 49,308 Depreciation and amortization $ 27,052 $ 6,720 $ 11,550 $ 4,083 $ 8,664 58,069 124,954 Losses on Asset Dispositions and Impairments, Net (116,222 ) Operating Loss $ (174,888 ) As of December 31, 2016 Property and Equipment: Historical cost $ 404,226 $ 136,428 $ 197,389 $ 57,744 $ 162,972 $ 958,759 Accumulated depreciation (233,075 ) (60,794 ) (97,433 ) (34,455 ) (114,862 ) (540,619 ) $ 171,151 $ 75,634 $ 99,956 $ 23,289 $ 48,110 $ 418,140 Total Assets (1) $ 325,190 $ 96,847 $ 140,166 $ 94,373 $ 84,783 $ 992,692 ( 1 Total assets exclude $22,427 The Company's investments in 50% December 31, 2018, 50% 50% $53.8 $65.8 4 50% December 31 2018 2017 2016 MexMar $ 2,736 $ 10,103 $ 3,556 Other (6,151 ) (6,026 ) (9,870 ) $ (3,415 ) $ 4,077 $ (6,314 )

Note 19 - Supplemental Informat

Note 19 - Supplemental Information for Statements of Cash Flows	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Cash Flow, Supplemental Disclosures [Text Block]	19. SUPPLEMENTAL INFORMATION FOR STATEMENTS OF CASH FLOWS Supplemental information for the years ended December 31 2018 2017 2016 Income taxes (paid) refunded, net $ (316 ) $ 33,773 $ 10,224 Interest paid, excluding capitalized interest 21,031 9,216 2,698 Exchange of receivable for investment in 50% or less owned company — 1,000 — Equipment received to settle notes receivable — — 11,900

Note 20 - Subsequent Events

Note 20 - Subsequent Events	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Subsequent Events [Text Block]	20. SUBSEQUENT EVENTS On January 9, 2019, three 603,872 ten four On January 25, 2019, 6.25% not one two £1,552,780 $2.0 6.25% not two 100%

Note 21 - Quarterly Financial I

Note 21 - Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
Quarterly Financial Information [Text Block]	21. QUARTERLY FINANCIAL INFORMATION (UNAUDITED) Selected financial information for interim quarterly periods is presented below (in thousands, except share data). Earnings (loss) per common share of SEACOR Marine Holdings Inc. are computed independently for each of the quarters presented and the sum of the quarterly earnings per share may not Three Months Ended Dec. 31, Sept. 30, June 30, March 31, 2018 Operating Revenues $ 70,932 $ 70,255 $ 60,701 $ 51,721 Operating Loss (11,189 ) (10,158 ) (21,002 ) (24,414 ) Net Loss (7,969 ) (15,766 ) (26,629 ) (31,688 ) Net Loss attributable to SEACOR Marine Holdings Inc. (7,794 ) (15,957 ) (25,024 ) (28,833 ) Basic Loss Per Common Share of SEACOR Marine Holdings Inc. $ (0.35 ) $ (0.71 ) $ (1.19 ) $ (1.64 ) Diluted Loss Per Common Share of SEACOR Marine Holdings Inc. $ (0.35 ) $ (0.71 ) $ (1.19 ) $ (1.64 ) 2017 Operating Revenues $ 49,343 $ 47,813 $ 42,323 $ 34,304 Operating Loss (35,830 ) (29,129 ) (44,815 ) (18,585 ) Net Income (Loss) 27,904 (22,356 ) (36,489 ) (7,599 ) Net Income (Loss) attributable to SEACOR Marine Holdings Inc. 28,961 (20,475 ) (33,992 ) (7,395 ) Basic Income (Loss) Per Common Share of SEACOR Marine Holdings Inc. $ 1.65 $ (1.17 ) $ (1.93 ) $ (0.42 ) Diluted Income (Loss) Per Common Share of SEACOR Marine Holdings Inc. $ 1.20 $ (1.25 ) $ (1.93 ) $ (0.42 )

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2018
Notes to Financial Statements
SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]	SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS For the Years Ended December 31, 201 8 , 201 7 and 201 6 (in thousands) Description Balance Beginning of Year Charges (Recoveries) to Cost and Expenses Deductions (1) Balance End of Year Year Ended December 31, 2018 Allowance for doubtful accounts (deducted from trade and notes receivable) $ 4,039 $ (928 ) $ (2,251 ) $ 860 Year Ended December 31, 2017 Allowance for doubtful accounts (deducted from trade and notes receivable) $ 5,359 $ (1,283 ) $ (37 ) $ 4,039 Year Ended December 31, 2016 Allowance for doubtful accounts (deducted from trade and notes receivable) $ 1,177 $ 4,280 $ (98 ) $ 5,359 ( 1 Trade receivable amounts deemed uncollectible that were removed from accounts receivable and allowance for doubtful accounts.

Significant Accounting Policies

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Segment Reporting, Policy [Policy Text Block]	Nature of Operations and Segmentation. Accounting standards require public business enterprises to report information about each of their operating business segments that exceed certain quantitative thresholds or meet certain other reporting requirements. Operating business segments have been defined as a component of an enterprise about which separate financial information is available and is evaluated regularly by the chief operating decision maker in assessing performance. The Company has identified the following five United States, primarily Gulf of Mexico. Africa, primarily West Africa. Middle East and Asia. Brazil, Mexico, Central and South America. December 31, 2018, 34 seven 27 49% 49% Europe, primarily North Sea. 1991 40 36 four The Spin-off. June 1, 2017, May 22, 2017 ( two
Consolidation, Policy [Policy Text Block]	Basis of Consolidation. 50% Noncontrolling interests in consolidated subsidiaries are included in the consolidated balance sheets as a separate component of equity. The Company reports consolidated net income (loss) inclusive of both the Company's and the noncontrolling interests' share, as well as the amounts of consolidated net income (loss) attributable to each of the Company and the noncontrolling interests. If a subsidiary is deconsolidated upon a change in control, any retained noncontrolled equity investment in the former controlled subsidiary is measured at fair value and a gain or loss is recognized in net income (loss) based on such fair value. If a subsidiary is consolidated upon a change in control, any previous noncontrolled equity investment in the subsidiary is measured at fair value and a gain or loss is recognized in net income (loss) based on such fair value. The Company employs the equity method of accounting for investments in 50% not 20% 50% may 20%. may 50% may not may 50% may 50% 50% 50% The Company employs the cost method of accounting for investments in 50% not
Use of Estimates, Policy [Policy Text Block]	Use of Estimates. may
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition. The Company contracts with various customers to carry out management services for vessels as agents for and on behalf of ship owners. These services include crew management, technical management, commercial management, insurance arrangements, sale and purchase of vessels, provisions and bunkering. As the manager of the vessels, the Company undertakes to use its best endeavors to provide the agreed management services as agents for and on behalf of the owners in accordance with sound ship management practice and to protect and promote the interest of the owners in all matters relating to the provision of services hereunder. The Company also contracts with various customers to carry out management services regarding engineering for vessel construction and vessel conversions. The vast majority of the ship management agreements span over the length of one three 18 Revenue that does not December 31 201 8 201 7 201 6 Balance at beginning of year $ 10,104 $ 6,953 $ 6,953 Revenues deferred during the year 3,600 4,699 — Revenues recognized during the year (12,377 ) (1,548 ) — Balance at end of year $ 1,327 $ 10,104 $ 6,953 As of December 31, 2018, of $6.8 August 17, 2012, 11 December 31, 2018 Also, as of December 31, 2018, $1.3 not 606, no The Company earns revenue primarily from the time charter and bareboat charter of vessels to customers. Since the Company charges customers based upon daily rates of hire, vessel revenues are recognized on a daily basis throughout the contract period. Under a time charter, the Company provides a vessel to a customer and is responsible for all operating expenses, typically excluding fuel. Under a bareboat charter, the Company provides a vessel to a customer and the customer assumes responsibility for all operating expenses and assumes all risks of operation. In the U.S. Gulf of Mexico, time charter durations and rates are typically established in the context of master service agreements that govern the terms and conditions of the charter. From time to time, the Company may Contract or charter durations may not two may
Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block]	Cash Equivalents. three
Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]	Restricted Cash. For the year ended December 31, 2018 2017 2016 Cash $ 95,195 $ 110,234 $ 117,309 Cash equivalents — — — Restricted cash 1,657 2,317 1,462 Total $ 96,852 $ 112,551 $ 118,771
Marketable Securities, Policy [Policy Text Block]	Marketable Securities.
Receivables, Policy [Policy Text Block]	Trade and Other Receivables. may
Derivatives, Policy [Policy Text Block]	Derivative Instruments. not 50% 50%
Concentration Risk, Credit Risk, Policy [Policy Text Block]	Concentrations of Credit Risk. not not not
Inventory, Policy [Policy Text Block]	Inventories. first first December 31, 2018, $0.2 no December 31, 2017 2016.
Property, Plant and Equipment, Policy [Policy Text Block]	Property and Equipment. not may As of December 31, 2018, Offshore Support Vessels: Crew transfer vessels 10 All other offshore support vessels (excluding crew transfer) 20 The Company's property and equipment as of December 31 Historical Cost (1) Accumulated Depreciation Net Book Value 201 8 Offshore support vessels: AHTS $ 197,343 $ (168,731 ) $ 28,612 FSV (2) 404,310 (98,580 ) 305,730 Supply 64,284 (37,202 ) 27,082 Standby safety 123,731 (97,951 ) 25,780 Specialty 25,683 (20,433 ) 5,250 Liftboats 329,473 (71,887 ) 257,586 Crew transfer 73,589 (46,614 ) 26,975 General machinery and spares 8,457 (8,390 ) 67 Other (3) 15,863 (11,484 ) 4,379 $ 1,242,733 $ (561,272 ) $ 681,461 2017 Offshore support vessels: AHTS $ 198,222 $ (174,159 ) $ 24,063 FSV (2) 424,865 (89,980 ) 334,885 Supply 105,360 (51,494 ) 53,866 Standby safety 118,414 (97,603 ) 20,811 Specialty 30,529 (19,304 ) 11,225 Liftboats 196,504 (54,161 ) 142,343 Crew transfer 65,976 (40,358 ) 25,618 General machinery and spares 14,385 (13,244 ) 1,141 Other (3) 25,581 (19,857 ) 5,724 $ 1,179,836 $ (560,160 ) $ 619,676 ( 1 Includes property and equipment acquired in business acquisitions at acquisition date fair value, and net of the impact of recognized impairment charges. ( 2 Fast support vessels ("FSVs"). ( 3 Includes land, buildings, leasehold improvements, vehicles and other property and equipment. Depreciation and amortization expense totaled $72.2 $62.8 $58.0 2018, 2017 2016, Equipment maintenance and repair costs and the costs of routine overhauls, drydockings and inspections performed on vessels and equipment are charged to operating expense as incurred. Expenditures that extend the useful life or improve the marketing and commercial characteristics of vessels, as well as major renewals and improvements to other properties, are capitalized. Certain interest costs incurred during the construction of vessels are capitalized as part of the vessels' carrying values and are amortized over such vessels' estimated useful lives. Capitalized interest totaled $2.4 $3.6 $7.0 2018, 2017 2016,
Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block]	Intangible Assets. December 31, 2016, Impairment of Long-Lived Assets 2016, $0.1
Impairment or Disposal of Long-Lived Assets, Including Intangible Assets, Policy [Policy Text Block]	Impairment of Long-Lived Assets. may not As a result of the difficult conditions experienced in the offshore oil and natural gas markets beginning in the second 2014 During the year ended December 31, 2018, $14.6 four three one December 31, 2017, $27.5 one not one two December 31, 2016, $119.7 one vessels (see Note 10 three The Company's other vessel classes and other individual vessels in active service and cold-stacked status, for which no For vessel classes and individual vessels with indicators of impairment but not December 31, 2018, may Impairment of 50% 50% may December 31, 2018, 2017 2016, $1.2 $8.8 $6.9 50% 4
Business Combinations Policy [Policy Text Block]	Business Combinations. 100% 2
Deferred Charges, Policy [Policy Text Block]	Debt Discount and Issue Costs .
Self Insurance Reserve [Policy Text Block]	Self-insurance Liabilities . may
Income Tax, Policy [Policy Text Block]	Income Taxes . not not The Global Intangible Low Taxed Income ("GILTI") regime effectively imposes a minimum tax on worldwide foreign earnings and subjects U.S. shareholders of controlled foreign corporations ("CFCs") to current taxation on certain income earned through a CFC. The Company has made the policy election to record any liability, associated with GILTI in the period in which it is incurred. Prior to the Spin-off, SEACOR Marine was included in the consolidated U.S. federal income tax return of SEACOR Holdings. SEACOR Holdings' policy for allocation of U.S. federal income taxes required its domestic subsidiaries included in the consolidated U.S. federal income tax return to compute their provision for U.S. federal income taxes on a separate company basis and settle with SEACOR Holdings. In the normal course of business, the Company or SEACOR Holdings may may not not not
Deferred Gains [Policy Text Block]	Deferred Gains - Vessel Sale-Leaseback Transactions and Financed Vessel Sales . third 50% not 6 not December 31 2018 2017 2016 Balance at beginning of year $ 23,553 $ 32,035 $ 40,234 Amortization of deferred gains included in operating expenses as reduction to rental expense (8,037 ) (8,118 ) (8,199 ) Recognition of deferred gains included in losses on asset dispositions and impairments, net (4,490 ) — — Other — (364 ) — Balance at end of year $ 11,026 $ 23,553 $ 32,035 Deferred Gains - Vessel Sales to the Company's 50% 50% 50% 50% 50% December 31 201 8 2017 2016 Balance at beginning of year $ 1,453 $ 1,875 $ 3,064 Amortization of deferred gains included in losses on asset dispositions and impairments, net (25 ) — (36 ) Other (635 ) (422 ) (1,153 ) Balance at end of year $ 793 $ 1,453 $ 1,875
Foreign Currency Transactions and Translations Policy [Policy Text Block]	Foreign Currency Translation. Foreign Currency Transactions.
Comprehensive Income, Policy [Policy Text Block]	Accumulated Other Comprehensive Loss. SEACOR Marine Holdings Inc. Stockholders' Equity Noncontrolling Interests Foreign Currency Translation Adjustments Derivative Gains (Losses) on Cash Flow Hedges, net Total Foreign Currency Translation Adjustments Derivative Gains (Losses) on Cash Flow Hedges, net Other Comprehensive Loss Year Ended December 31, 2015 $ (5,985 ) $ (110 ) $ (6,095 ) $ (529 ) $ — Other comprehensive (loss) income (8,351 ) 286 (8,065 ) (1,085 ) (17 ) $ (9,167 ) Income tax benefit (expense) 2,923 (100 ) 2,823 — — 2,823 Year Ended December 31, 2016 (11,413 ) 76 (11,337 ) (1,614 ) (17 ) $ (6,344 ) Other comprehensive income 4,397 703 5,100 257 18 $ 5,375 Income tax (expense) (1) (6,179 ) (77 ) (6,256 ) — — (6,256 ) Year Ended December 31, 2017 (13,195 ) 702 (12,493 ) (1,357 ) 1 $ (881 ) Other comprehensive loss (2,277 ) (1,972 ) (4,249 ) (88 ) (12 ) $ (4,349 ) Income tax expense — (46 ) (46 ) — — (46 ) Year Ended December 31, 2018 $ (15,472 ) $ (1,316 ) $ (16,788 ) $ (1,445 ) $ (11 ) $ (4,395 ) ( 1 For the year ended December 31, 2017, $4.5 December 22, 2017.
Earnings Per Share, Policy [Policy Text Block]	Loss Per Share. Basi December 31, 2018, 2017 2016, 2,183,708 4,070,500 4,070,500 December 31, 2018 2017, 192,346 121,693 805,566 613,700
New Accounting Pronouncements, Policy [Policy Text Block]	New Accounting Pronouncements. On May 28, 2014, 2014 09, "Revenue from Contracts with Customers (Topic 606 January 1, 2018 not not On February 25, 2016, January 1, 2019 January 1, 2019 $33.9 $32.1 n in lea $1.8 four $8.7 On October 24, 2016, January 1, 2018, $12.1 On Augu st 28, 2018, No. 2018 13, Fair Value Measurement (Topic 820 . This new guidance modifies the disclosure requirements related to fair value measurement. The new guidance is effective for fiscal years beginning after December 15, 2019. not On August 29 2018, No. 2018 15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350 40 December 15, 2019, not

Note 1 - Nature of Operations_2

Note 1 - Nature of Operations and Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Deferred Revenue, by Arrangement, Disclosure [Table Text Block]	201 8 201 7 201 6 Balance at beginning of year $ 10,104 $ 6,953 $ 6,953 Revenues deferred during the year 3,600 4,699 — Revenues recognized during the year (12,377 ) (1,548 ) — Balance at end of year $ 1,327 $ 10,104 $ 6,953
Schedule of Cash, Cash Equivalents and Restricted Cash [Table Text Block]	2018 2017 2016 Cash $ 95,195 $ 110,234 $ 117,309 Cash equivalents — — — Restricted cash 1,657 2,317 1,462 Total $ 96,852 $ 112,551 $ 118,771
Property, Plant and Equipment, Estimated Useful Life [Table Text Block]	Offshore Support Vessels: Crew transfer vessels 10 All other offshore support vessels (excluding crew transfer) 20
Property, Plant and Equipment [Table Text Block]	Historical Cost (1) Accumulated Depreciation Net Book Value 201 8 Offshore support vessels: AHTS $ 197,343 $ (168,731 ) $ 28,612 FSV (2) 404,310 (98,580 ) 305,730 Supply 64,284 (37,202 ) 27,082 Standby safety 123,731 (97,951 ) 25,780 Specialty 25,683 (20,433 ) 5,250 Liftboats 329,473 (71,887 ) 257,586 Crew transfer 73,589 (46,614 ) 26,975 General machinery and spares 8,457 (8,390 ) 67 Other (3) 15,863 (11,484 ) 4,379 $ 1,242,733 $ (561,272 ) $ 681,461 2017 Offshore support vessels: AHTS $ 198,222 $ (174,159 ) $ 24,063 FSV (2) 424,865 (89,980 ) 334,885 Supply 105,360 (51,494 ) 53,866 Standby safety 118,414 (97,603 ) 20,811 Specialty 30,529 (19,304 ) 11,225 Liftboats 196,504 (54,161 ) 142,343 Crew transfer 65,976 (40,358 ) 25,618 General machinery and spares 14,385 (13,244 ) 1,141 Other (3) 25,581 (19,857 ) 5,724 $ 1,179,836 $ (560,160 ) $ 619,676
Schedule of Deferred Gain [Table Text Block]	2018 2017 2016 Balance at beginning of year $ 23,553 $ 32,035 $ 40,234 Amortization of deferred gains included in operating expenses as reduction to rental expense (8,037 ) (8,118 ) (8,199 ) Recognition of deferred gains included in losses on asset dispositions and impairments, net (4,490 ) — — Other — (364 ) — Balance at end of year $ 11,026 $ 23,553 $ 32,035 201 8 2017 2016 Balance at beginning of year $ 1,453 $ 1,875 $ 3,064 Amortization of deferred gains included in losses on asset dispositions and impairments, net (25 ) — (36 ) Other (635 ) (422 ) (1,153 ) Balance at end of year $ 793 $ 1,453 $ 1,875
Comprehensive Income (Loss) [Table Text Block]	SEACOR Marine Holdings Inc. Stockholders' Equity Noncontrolling Interests Foreign Currency Translation Adjustments Derivative Gains (Losses) on Cash Flow Hedges, net Total Foreign Currency Translation Adjustments Derivative Gains (Losses) on Cash Flow Hedges, net Other Comprehensive Loss Year Ended December 31, 2015 $ (5,985 ) $ (110 ) $ (6,095 ) $ (529 ) $ — Other comprehensive (loss) income (8,351 ) 286 (8,065 ) (1,085 ) (17 ) $ (9,167 ) Income tax benefit (expense) 2,923 (100 ) 2,823 — — 2,823 Year Ended December 31, 2016 (11,413 ) 76 (11,337 ) (1,614 ) (17 ) $ (6,344 ) Other comprehensive income 4,397 703 5,100 257 18 $ 5,375 Income tax (expense) (1) (6,179 ) (77 ) (6,256 ) — — (6,256 ) Year Ended December 31, 2017 (13,195 ) 702 (12,493 ) (1,357 ) 1 $ (881 ) Other comprehensive loss (2,277 ) (1,972 ) (4,249 ) (88 ) (12 ) $ (4,349 ) Income tax expense — (46 ) (46 ) — — (46 ) Year Ended December 31, 2018 $ (15,472 ) $ (1,316 ) $ (16,788 ) $ (1,445 ) $ (11 ) $ (4,395 )

Note 2 - Business Acquisitions

Note 2 - Business Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	2018 2 Trade and other receivables $ — $ 235 Other current assets 211 4,148 Investments, at Equity, and Advances to 50% or Less Owned Companies — (15,700 ) Property and Equipment 140,257 61,626 Accounts payable — 747 Other current liabilities — (76 ) Long-Term Debt (106,640 ) (41,186 ) Other — (43 ) Minority Interest (18,828 ) — Purchase price (1) $ 15,000 $ 9,751

Note 3 - Equipment Acquisitio_2

Note 3 - Equipment Acquisitions and Dispositions (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Shedule of Vessel Acquired and Disposed of [Table Text Block]	2018 (1) 2017 2016 FSV — 6 12 Supply — 5 2 Specialty — — 1 Liftboat 6 — — Crew transfer 2 — 2 8 11 17 2018 (1) 2017 2016 AHTS 1 — — FSV 9 — — Standby safety 3 1 4 Supply — 1 5 Crew transfer 1 — — Liftboats 2 2 — 16 4 9

Note 4 - Investments, at Equi_2

Note 4 - Investments, at Equity, and Advances to 50% or Less Owned Companies (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Equity Method Investments [Table Text Block]	Ownership 2018 2017 MexMar 49.0% $ 53,840 $ 60,980 SEACOSCO 50.0% 28,002 — OSV Partners 30.4% 11,087 10,006 SEACOR Marlin 49.0% 7,579 — MEXMAR Offshore International 49.0% 4,900 — Offshore Vessel Holdings 49.0% 4,900 — Dynamic Offshore Drilling 19.0% 2,263 4,958 Nautical Power 50.0% — 6,408 Other 20.0% — 50.0% 9,202 9,817 $ 121,773 $ 92,169 2018 2017 Current assets $ 38,113 $ 71,990 Noncurrent assets 215,207 194,990 Current liabilities 27,610 23,931 Noncurrent liabilities 115,948 147,043 2018 2 017 2016 Operating Revenues $ 57,003 $ 67,003 $ 70,521 Costs and Expenses: Operating and administrative 25,932 29,405 37,613 Depreciation 16,295 15,977 13,958 42,227 45,382 51,571 Operating Income $ 14,776 $ 21,621 $ 18,950 Net Income $ 5,584 $ 9,233 $ 6,476 201 7 (1) 201 6 Operating Revenues $ 5,075 $ 21,611 Costs and Expenses: Operating and administrative 3,752 12,837 Depreciation 2,324 3,694 6,076 16,531 Operating (Loss) Income $ (1,001 ) $ 5,080 Net (Loss) Income $ (2,699 ) $ 778 2018 2017 Current assets $ 61,287 $ 61,360 Noncurrent assets 352,421 247,038 Current liabilities 32,302 14,603 Noncurrent liabilities 209,752 138,789 2018 2017 2016 Operating Revenues $ 54,853 $ 77,409 $ 77,571 Costs and Expenses: Operating and administrative 53,967 46,748 51,136 Depreciation 10,148 12,198 13,181 64,115 58,946 64,317 Loss on Asset Dispositions and Impairments, Net (89 ) — (21,323 ) Operating (Loss) Income $ (9,351 ) $ 18,463 $ (8,069 ) Net (Loss) Income $ (20,383 ) $ 6,451 $ (19,229 )
Assets of Investment in Non-controlling Interest [Table Text Block]	Cash $ 1,943 Marketable securities 785 Trade and other receivables (291 ) Investments, at Equity, and Advances to 50% or Less Owned Companies (19,374 ) Property and Equipment 96,000 Accounts payable 3,201 Other current liabilities 1,153 Long-Term Debt 58,335 Other Liabilities (1,000 ) Noncontrolling interests in subsidiaries 17,374

Note 5 - Construction Reserve_2

Note 5 - Construction Reserve Funds (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Other Assets, Noncurrent [Table Text Block]	2018 2017 2016 Withdrawals $ (17,300 ) $ (39,163 ) $ (87,820 ) Deposits — 6,315 27,414 $ (17,300 ) $ (32,848 ) $ (60,406 )

Note 6 - Leases (Tables)

Note 6 - Leases (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	2019 $ 14,288 2020 13,826 2021 6,480 2022 331 2023 and beyond 661

Note 7 - Long-term Debt (Tables

Note 7 - Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Long-term Debt Instruments [Table Text Block]	2018 2017 SEACOR Marine Foreign Holdings Syndicated Credit Facility $ 126,750 $ — Convertible Senior Notes 125,000 175,000 Falcon Global USA Term Loan Facility 109,099 — Sea-Cat Crewzer III Term Loan Facility 25,989 29,078 Windcat Workboats Facilities 24,850 25,202 Falcon Global USA Revolver 15,000 — SEACOR 88/888 Term Loan 11,000 — BNDES Equipment Construction Finance Notes 5,284 7,234 Falcon Global International Term Loan Facility — 54,870 Sea-Cat Crewzer II Term Loan Facility — 20,871 Sea-Cat Crewzer Term Loan Facility — 18,504 C-Lift Acquisition Notes — 16,000 Cypress CKOR Term Loan — 1,300 442,972 348,059 Portion due within one year (16,812 ) (22,858 ) Debt discount (32,005 ) (27,373 ) Issue costs (6,301 ) (5,787 ) $ 387,854 $ 292,041
Schedule of Maturities of Long-term Debt [Table Text Block]	2019 $ 16,812 2020 25,489 2021 51,381 2022 25,150 2023 222,900 Years subsequent to 2023 101,240 $ 442,972

Note 8 - Income Taxes (Tables)

Note 8 - Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	2018 2017 2016 United States $ (72,540 ) $ (90,696 ) $ (169,523 ) Foreign (28,226 ) (45,112 ) (28,095 ) Eliminations 8,782 18,785 7,313 $ (91,984 ) $ (117,023 ) $ (190,305 )
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	201 8 201 7 201 6 Current: Federal $ 5,987 $ (16,705 ) $ (20,718 ) State 3 (42 ) (139 ) Foreign 3,400 3,347 5,436 9,390 (13,400 ) (15,421 ) Deferred: Federal (21,466 ) (60,750 ) (47,692 ) State (1,404 ) (172 ) (446 ) Foreign 133 (84 ) 90 (22,737 ) (61,006 ) (48,048 ) $ (13,347 ) $ (74,406 ) $ (63,469 )
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	2018 2017 2016 Statutory rate (21.0 )% (35.0 )% (35.0 )% U.S. federal income tax law changes — % (37.3 )% — % SEACOR Holdings share awards to Company personnel 0.2 % 2.3 % 0.4 % Non-deductible expenses — % 1.8 % 0.1 % Exclusion of foreign subsidiaries with accumulated losses and withholding tax 9.3 % 2.7 % 1.1 % Noncontrolling interests (1.5 )% 1.7 % 0.2 % State taxes (1.5 )% (0.2 )% (0.3 )% Other 0.0 % 0.4 % 0.1 % (14.5 )% (63.6 )% (33.4 )%
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	2018 2017 Deferred tax liabilities: Property and equipment $ 65,880 $ 55,262 Investments in 50% or Less Owned Companies 3,040 4,258 Other 7,789 5,901 Total deferred tax liabilities 76,709 65,421 Deferred tax assets: Federal Net Operating Loss Carryforwards 20,974 5,111 Other 11,677 5,373 32,651 10,484 Valuation Allowance (624 ) (569 ) Total deferred tax assets 32,027 9,915 Net deferred tax liabilities $ 44,682 $ 55,506

Note 9 - Derivative Instrumen_2

Note 9 - Derivative Instruments and Hedging Strategies (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]	Balance Sheet 2018 2017 Classification Derivative Asset Derivative Liability Derivative Asset Derivative Liability Derivatives designated as hedging instruments: Interest rate swap agreements (cash flow hedges) Current $ — $ 1,659 $ 260 $ 20 — 1,659 260 20 Derivatives not designated as hedging instruments: Conversion option liability on Convertible Senior Notes Long-Term — 5,276 — 6,832 Interest rate swap agreements Current — — 159 46 $ — $ 6,935 $ 419 $ 6,898
Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) [Table Text Block]	Gain (Loss) Recognized in OCI on Derivatives (Effective Portion) Derivatives in Cash Flow Hedging Relationships 2018 2017 2016 Interest rate swap contracts $ (1,939 ) $ 214 $ (2,493 ) Joint venture interest rate swap contracts (76 ) 389 2,744 Gain (Loss) Reclassified from OCI into Income (Effective Portion) Location of Gain 2018 2017 2016 Interest expense $ 31 118 18
Derivatives Not Designated as Hedging Instruments [Table Text Block]	Derivative gains (losses), net 201 8 201 7 201 6 Conversion option liability on Convertible Senior Notes $ 1,556 $ 20,422 $ — Interest rate swap agreements 1,298 46 (18 ) Options on equities — — 3,095 Forward currency exchange, option and future contracts — (212 ) (82 ) $ 2,855 $ 20,256 $ 2,995

Note 10 - Fair Value Measurem_2

Note 10 - Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	Level 1 Level 2 Level 3 (1) 2018 ASSETS Construction reserve funds $ 28,221 $ — $ — LIABILITIES Derivative instruments (included in other current liabilities) — 1,659 — Conversion Option Liability on Convertible Senior Notes — — 5,276 2017 ASSETS Derivative instruments (included in other receivables) $ — $ 419 $ — Construction reserve funds 45,361 — — LIABILITIES Derivative instruments (included in other current liabilities) — 66 — Conversion Option Liability on Convertible Senior Notes — — 6,832
Fair Value, by Balance Sheet Grouping [Table Text Block]	Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 201 8 ASSETS Cash, cash equivalents and restricted cash $ 96,852 $ 96,852 $ — $ — Investments, at cost, in 50% or less owned companies (included in other assets) see below LIABILITIES Long-term debt, including current portion 404,666 — 388,949 — 201 7 ASSETS Cash, cash equivalents and restricted cash $ 112,551 $ 112,551 $ — $ — Investments, at cost, in 50% or less owned companies (included in other assets) 132 see below LIABILITIES Long-term debt, including current portion 314,899 — 291,932 —
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block]	Level 1 Level 2 Level 3 2018 ASSETS Property and equipment: AHTS $ — $ 2,000 $ — Liftboats — — 134,775 Specialty — 4,500 — 2017 ASSETS Property and equipment: AHTS $ — $ 12,400 $ — FSV — 175 — Specialty — 750 — Investments, at equity, in 50% or less owned companies — 20,658 20,430

Note 13 - Noncontrolling Inte_2

Note 13 - Noncontrolling Interests in Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Noncontrolling Interest [Table Text Block]	Noncontrolling Interests 2018 2017 Falcon Global Holdings 28.0% $ 26,989 $ 12,087 Windcat Workboats 12.5% 2,115 2,608 Other 1.8% 300 280 $ 29,404 $ 14,975

Note 15 - Share Based Compens_2

Note 15 - Share Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Share-based Compensation, Activity [Table Text Block]	2018 2017 Director Stock Awards Granted 19,285 3,000 Restricted Stock Activity: Outstanding as of the beginning of year 121,693 — Granted - 2017 Plan 120,600 1,000 Distributed by SEACOR Holdings in connection with the Spin-off — 120,693 Vested 49,947 — Forfeited — — Outstanding as of the end of year 192,346 121,693 Stock Option Activity: Outstanding as of the beginning of year 613,700 — Granted - 2017 Plan 258,491 613,700 Exercised 66,625 — Forfeited — — Expired — — Outstanding as of the end of year 805,566 613,700
Nonvested Restricted Stock Shares Activity [Table Text Block]	Restricted Stock Number of Shares Weight Average Grant Price Non-Vested as of December 31, 2017 121,693 $ 24.01 Granted 120,600 12.63 Vested 49,947 24.85 Non-Vested as of December 31, 2018 192,346 22.32
Share-based Compensation, Stock Options, Activity [Table Text Block]	Stock Options Number of Shares Weight Average Grant Price Non-Vested as of December 31, 2017 613,700 $ 12.50 Granted 258,491 19.70 Exercised 66,625 12.50 Non-Vested as of December 31, 2018 805,566 14.81 Exercisable as of December 31, 2018 (1) 261,691 14.02

Note 16 - Related Party Trans_2

Note 16 - Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Related Party Transactions [Table Text Block]	2018 2017 2016 Participation in SEACOR Holdings employee benefit plans $ — $ 899 $ 3,702 Participation in SEACOR Holdings share award plans — 8,383 4,588 Shared services allocation for administrative support — 1,932 4,365 $ — $ 11,214 $ 12,655

Note 17 - Commitments and Con_2

Note 17 - Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Unrecorded Unconditional Purchase Obligations Disclosure [Table Text Block]	2019 $ 51,132 2020 27,046 $ 78,178

Note 18 - Major Customers and_2

Note 18 - Major Customers and Segment Information (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Segment Reporting Information, by Segment [Table Text Block]	United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Brazil, Mexico, Central and South America Europe (primarily North Sea) Total For the year ended December 31, 2018 Operating Revenues: Time charter $ 38,802 $ 43,847 $ 50,072 $ 17,343 $ 72,188 $ 222,252 Bareboat charter — — — 4,635 — 4,635 Other 14,762 7,661 (887 ) 1,554 3,632 26,722 53,564 51,508 49,185 23,532 75,820 253,609 Direct Costs and Expenses: Operating: Personnel 18,708 16,538 16,806 4,399 38,577 95,028 Repairs and maintenance 5,152 6,330 11,172 1,011 9,614 33,279 Drydocking 1,957 2,085 1,362 128 6,055 11,587 Insurance and loss reserves 2,922 1,096 1,371 495 1,190 7,074 Fuel, lubes and supplies 3,568 3,826 4,027 1,225 4,329 16,975 Other 393 4,313 3,980 1,130 1,332 11,148 32,700 34,188 38,718 8,388 61,097 175,091 Direct Vessel Profit $ 20,864 $ 17,320 $ 10,467 $ 15,144 $ 14,723 78,518 Other Costs and Expenses: Operating: Leased-in equipment $ 7,420 $ 3,843 $ — $ — $ 212 11,475 Administrative and general 52,813 Depreciation and amortization $ 23,227 $ 10,453 $ 18,762 $ 7,908 $ 11,896 72,246 136,534 Losses on Asset Dispositions and Impairments, Net (8,747 ) Operating Loss $ (66,763 ) As of December 31, 2018 Property and Equipment: Historical cost $ 432,336 $ 184,361 $ 306,897 $ 124,177 $ 194,963 $ 1,242,734 Accumulated depreciation (224,737 ) (55,206 ) (81,378 ) (57,002 ) (142,949 ) (561,272 ) $ 207,599 $ 129,155 $ 225,519 $ 67,175 $ 52,014 $ 681,462 Total Assets (1) $ 351,748 $ 140,335 $ 260,002 $ 137,983 $ 59,716 $ 949,784 United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Brazil, Mexico, Central and South America Europe (primarily North Sea) Total For the year ended December 31, 2017 Operating Revenues: Time charter $ 18,079 $ 32,866 $ 33,410 $ 2,977 $ 73,213 $ 160,545 Bareboat charter — — — 4,636 — 4,636 Other 4,217 1,080 474 552 2,279 8,602 22,296 33,946 33,884 8,165 75,492 173,783 Direct Costs and Expenses: Operating: Personnel 15,621 13,419 16,883 809 34,768 81,500 Repairs and maintenance 3,594 5,957 9,037 274 8,793 27,655 Drydocking 1,828 2,180 968 — 4,059 9,035 Insurance and loss reserves 3,286 677 1,444 316 801 6,524 Fuel, lubes and supplies 1,485 2,815 3,727 223 3,782 12,032 Other 249 3,319 5,240 117 980 9,905 26,063 28,367 37,299 1,739 53,183 146,651 Direct Vessel Profit (Loss) $ (3,767 ) $ 5,579 $ (3,415 ) $ 6,426 $ 22,309 27,132 Other Costs and Expenses: Operating: Leased-in equipment $ 8,152 $ 3,870 $ 862 $ — $ 64 12,948 Administrative and general 56,217 Depreciation and amortization $ 22,060 $ 9,280 $ 17,724 $ 3,608 $ 10,107 62,779 131,944 Losses on Asset Dispositions and Impairments, Net (23,547 ) Operating Loss $ (128,359 ) As of December 31, 2017 Property and Equipment: Historical cost $ 410,475 $ 192,600 $ 326,378 $ 72,484 $ 177,899 $ 1,179,836 Accumulated depreciation (230,636 ) (57,228 ) (100,435 ) (37,281 ) (134,580 ) (560,160 ) $ 179,839 $ 135,372 $ 225,943 $ 35,203 $ 43,319 $ 619,676 Total Assets (1) $ 310,675 $ 140,173 $ 234,471 $ 103,135 $ 50,704 $ 839,158 United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Brazil, Mexico, Central and South America Europe (primarily North Sea) Total For the year ended December 31, 2016 Operating Revenues: Time charter $ 28,902 $ 36,706 $ 41,657 $ 196 $ 78,866 $ 186,327 Bareboat charter — — — 8,833 — 8,833 Other 3,954 856 12,230 1,180 2,256 20,476 32,856 37,562 53,887 10,209 81,122 215,636 Direct Costs and Expenses: Operating: Personnel 22,305 12,628 18,381 2,117 39,713 95,144 Repairs and maintenance 2,721 2,628 6,426 232 9,275 21,282 Drydocking 228 1,098 2,117 — 4,378 7,821 Insurance and loss reserves 3,363 539 731 43 1,006 5,682 Fuel, lubes and supplies 1,392 2,512 4,215 21 3,948 12,088 Other 271 2,519 3,247 114 1,180 7,331 30,280 21,924 35,117 2,527 59,500 149,348 Direct Vessel Profit $ 2,576 $ 15,638 $ 18,770 $ 7,682 $ 21,622 66,288 Other Costs and Expenses: Operating: Leased-in equipment $ 7,975 $ 3,898 $ 4,389 $ 913 $ 402 17,577 Administrative and general 49,308 Depreciation and amortization $ 27,052 $ 6,720 $ 11,550 $ 4,083 $ 8,664 58,069 124,954 Losses on Asset Dispositions and Impairments, Net (116,222 ) Operating Loss $ (174,888 ) As of December 31, 2016 Property and Equipment: Historical cost $ 404,226 $ 136,428 $ 197,389 $ 57,744 $ 162,972 $ 958,759 Accumulated depreciation (233,075 ) (60,794 ) (97,433 ) (34,455 ) (114,862 ) (540,619 ) $ 171,151 $ 75,634 $ 99,956 $ 23,289 $ 48,110 $ 418,140 Total Assets (1) $ 325,190 $ 96,847 $ 140,166 $ 94,373 $ 84,783 $ 992,692
Schedule of Income (Loss) in Equity Method Investment [Table Text Block]	2018 2017 2016 MexMar $ 2,736 $ 10,103 $ 3,556 Other (6,151 ) (6,026 ) (9,870 ) $ (3,415 ) $ 4,077 $ (6,314 )

Note 19 - Supplemental Inform_2

Note 19 - Supplemental Information for Statements of Cash Flows (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]	2018 2017 2016 Income taxes (paid) refunded, net $ (316 ) $ 33,773 $ 10,224 Interest paid, excluding capitalized interest 21,031 9,216 2,698 Exchange of receivable for investment in 50% or less owned company — 1,000 — Equipment received to settle notes receivable — — 11,900

Note 21 - Quarterly Financial_2

Note 21 - Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Quarterly Financial Information [Table Text Block]	Three Months Ended Dec. 31, Sept. 30, June 30, March 31, 2018 Operating Revenues $ 70,932 $ 70,255 $ 60,701 $ 51,721 Operating Loss (11,189 ) (10,158 ) (21,002 ) (24,414 ) Net Loss (7,969 ) (15,766 ) (26,629 ) (31,688 ) Net Loss attributable to SEACOR Marine Holdings Inc. (7,794 ) (15,957 ) (25,024 ) (28,833 ) Basic Loss Per Common Share of SEACOR Marine Holdings Inc. $ (0.35 ) $ (0.71 ) $ (1.19 ) $ (1.64 ) Diluted Loss Per Common Share of SEACOR Marine Holdings Inc. $ (0.35 ) $ (0.71 ) $ (1.19 ) $ (1.64 ) 2017 Operating Revenues $ 49,343 $ 47,813 $ 42,323 $ 34,304 Operating Loss (35,830 ) (29,129 ) (44,815 ) (18,585 ) Net Income (Loss) 27,904 (22,356 ) (36,489 ) (7,599 ) Net Income (Loss) attributable to SEACOR Marine Holdings Inc. 28,961 (20,475 ) (33,992 ) (7,395 ) Basic Income (Loss) Per Common Share of SEACOR Marine Holdings Inc. $ 1.65 $ (1.17 ) $ (1.93 ) $ (0.42 ) Diluted Income (Loss) Per Common Share of SEACOR Marine Holdings Inc. $ 1.20 $ (1.25 ) $ (1.93 ) $ (0.42 )

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts (Tables)	12 Months Ended
	Dec. 31, 2018
Notes Tables
Schedule II Valuation and Qualifying Accounts [Table Text Block]	Description Balance Beginning of Year Charges (Recoveries) to Cost and Expenses Deductions (1) Balance End of Year Year Ended December 31, 2018 Allowance for doubtful accounts (deducted from trade and notes receivable) $ 4,039 $ (928 ) $ (2,251 ) $ 860 Year Ended December 31, 2017 Allowance for doubtful accounts (deducted from trade and notes receivable) $ 5,359 $ (1,283 ) $ (37 ) $ 4,039 Year Ended December 31, 2016 Allowance for doubtful accounts (deducted from trade and notes receivable) $ 1,177 $ 4,280 $ (98 ) $ 5,359

Note 1 - Nature of Operations_3

Note 1 - Nature of Operations and Accounting Policies (Details Textual) $ in Thousands	Jan. 01, 2019USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)
Number of Reportable Segments			5
Contract with Customer, Liability, Total			$ 1,327	$ 10,104	$ 6,953	$ 6,953
Inventory Valuation Reserves, Ending Balance			200	0	0
Depreciation, Total			72,200	62,800	58,000
Capitalized Interest Costs, Including Allowance for Funds Used During Construction, Total			2,400	3,600	7,000
Amortization of Intangible Assets, Total					100
Impairment of Long-Lived Assets Held-for-use			14,600	27,500	119,700
Equity Method Investment, Other than Temporary Impairment			$ 1,200	8,800	$ 6,900
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount				$ 4,500
Incremental Common Shares Attributable to Conversion of Debt Securities, Total | shares			2,183,708	4,070,500	4,070,500
Accounting Standards Update 2016-02 [Member] | Subsequent Event [Member]
Operating Lease, Right-of-Use Asset	$ 33,900
Operating Lease, Liability, Total	32,100
Accounting Standards Update 2016-02 [Member] | Subsequent Event [Member] | Change in Accounting Principle for Equipment, Office and Land Leases [Member]
Cumulative Effect on Retained Earnings, Net of Tax, Total	1,800
Accounting Standards Update 2016-02 [Member] | Subsequent Event [Member] | Change in Accounting Principle for Unamortized Deferred Gains [Member]
Cumulative Effect on Retained Earnings, Net of Tax, Total	$ 8,700
Accounting Standards Update 2016-16 [Member]
Cumulative Effect on Retained Earnings, Net of Tax, Total		$ 12,100
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares			192,346	121,693
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares			805,566	613,700
Geographic Distribution, Domestic [Member]
Contract with Customer, Liability, Total			$ 6,800
Geographic Distribution, Foreign [Member]
Contract with Customer, Liability, Total			$ 1,300
MexMar [Member]
Equity Method Investment, Ownership Percentage			49.00%
MEXMAR Offshore [Member]
Equity Method Investment, Ownership Percentage			49.00%
Brazil, Mexico, Central and South America [Member]
Number of Vessels			34
Number of Vessels Owned			7
Number of Vessels Joint Ventured			27
Europe [Member]
Number of Vessels			40
Number of Vessels Owned			36
Number of Vessels Joint Ventured			4

Note 1 - Nature of Operations_4

Note 1 - Nature of Operations and Accounting Policies - Deferred Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Balance at beginning of year	$ 10,104	$ 6,953	$ 6,953
Revenues deferred during the year	3,600	4,699
Revenues recognized during the year	(12,377)	(1,548)
Balance at end of year	$ 1,327	$ 10,104	$ 6,953

Note 1 - Nature of Operations_5

Note 1 - Nature of Operations and Accounting Policies - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash	$ 95,195	$ 110,234	$ 117,309
Cash equivalents
Restricted cash	1,657	2,317	1,462
Total	$ 96,852	$ 112,551	$ 118,771

Note 1 - Nature of Operations_6

Note 1 - Nature of Operations and Accounting Policies - Property and Equipment Useful Life (Details)	12 Months Ended
	Dec. 31, 2018
Crew Transfer Vessels [Member]
Estimated useful life (Year)	10 years
All Other Offshore Support Vessels [Member]
Estimated useful life (Year)	20 years

Note 1 - Nature of Operations_7

Note 1 - Nature of Operations and Accounting Policies - Summary of Property and Equipment (Details) - USD ($) $ in Thousands		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Historical cost		$ 1,242,733	[1]	$ 1,179,836	[1]	$ 958,759
Accumulated depreciation		(561,272)		(560,160)		(540,619)
Net book value		681,461		619,676		$ 418,140
Offshore Support Vessels, Anchor Handling Towing Supply [Member]
Historical cost	[1]	197,343		198,222
Accumulated depreciation		(168,731)		(174,159)
Net book value		28,612		24,063
Fast Support Vessels [Member]
Historical cost	[1],[2]	404,310		424,865
Accumulated depreciation	[2]	(98,580)		(89,980)
Net book value	[2]	305,730		334,885
Offshore Support Vessels, Supply [Member]
Historical cost	[1]	64,284		105,360
Accumulated depreciation		(37,202)		(51,494)
Net book value		27,082		53,866
Offshore Support Vessels, Standby Safety [Member]
Historical cost	[1]	123,731		118,414
Accumulated depreciation		(97,951)		(97,603)
Net book value		25,780		20,811
Offshore Support Vessels, Specialty [Member]
Historical cost	[1]	25,683		30,529
Accumulated depreciation		(20,433)		(19,304)
Net book value		5,250		11,225
Offshore Support Vessels, Liftboats [Member]
Historical cost	[1]	329,473		196,504
Accumulated depreciation		(71,887)		(54,161)
Net book value		257,586		142,343
Crew Transfer Vessels [Member]
Historical cost	[1]	73,589		65,976
Accumulated depreciation		(46,614)		(40,358)
Net book value		26,975		25,618
General Machinery and Spares [Member]
Historical cost	[1]	8,457		14,385
Accumulated depreciation		(8,390)		(13,244)
Net book value		67		1,141
Property, Plant and Equipment, Other Types [Member]
Historical cost	[1],[3]	15,863		25,581
Accumulated depreciation	[3]	(11,484)		(19,857)
Net book value	[3]	$ 4,379		$ 5,724
[1]	Includes property and equipment acquired in business acquisitions at acquisition date fair value, and net of the impact of recognized impairment charges.
[2]	Fast support vessels ("FSVs").
[3]	Includes land, buildings, leasehold improvements, vehicles and other property and equipment.

Note 1 - Nature of Operations_8

Note 1 - Nature of Operations and Accounting Policies - Deferred Gain Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Sale-leaseback and Financed Equipment Sales [Member]
Balance at beginning of year	$ 23,553	$ 32,035	$ 40,234
Amortization of deferred gains	(8,037)	(8,118)	(8,199)
Recognition of deferred gains included in losses on asset dispositions and impairments, net	(4,490)
Other		(364)
Balance at end of year	11,026	23,553	32,035
Vessel Sales to Fifty Percent or Less Owned Subsidiaries [Member]
Balance at beginning of year	1,453	1,875	3,064
Amortization of deferred gains	(25)		(36)
Other	(635)	(422)	(1,153)
Balance at end of year	$ 793	$ 1,453	$ 1,875

Note 1 - Nature of Operations_9

Note 1 - Nature of Operations and Accounting Policies - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Balance	$ 523,166	$ 550,155		$ 689,854
Other comprehensive (loss) income	(4,349)	5,375		(9,167)
Income tax benefit (expense)	(46)	(6,256)		2,823
Other comprehensive (loss) income, net	(4,395)	(881)		(6,344)
Balance	554,935	523,166		550,155
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Balance	(13,195)	(11,413)		(5,985)
Other comprehensive (loss) income	(2,277)	4,397		(8,351)
Income tax benefit (expense)		(6,179)	[1]	2,923
Balance	(15,472)	(13,195)		(11,413)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Balance	702	76		(110)
Other comprehensive (loss) income	(1,972)	703		286
Income tax benefit (expense)	(46)	(77)	[1]	(100)
Balance	(1,316)	702		76
AOCI Attributable to Parent [Member]
Balance	(12,493)	(11,337)		(6,095)
Other comprehensive (loss) income	(4,249)	5,100		(8,065)
Income tax benefit (expense)	(46)	(6,256)	[1]	2,823
Other comprehensive (loss) income, net	(4,295)	(1,156)		(5,242)
Balance	(16,788)	(12,493)		(11,337)
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest [Member]
Balance	(1,357)	(1,614)		(529)
Other comprehensive (loss) income	(88)	257		(1,085)
Income tax benefit (expense)			[1]
Balance	(1,445)	(1,357)		(1,614)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Noncontrolling Interest [Member]
Balance	1	(17)
Other comprehensive (loss) income	(12)	18		(17)
Income tax benefit (expense)			[1]
Balance	(11)	1		(17)
AOCI Attributable to Noncontrolling Interest [Member]
Other comprehensive (loss) income	(4,349)	5,375		(9,167)
Income tax benefit (expense)	(46)	(6,256)		2,823
Other comprehensive (loss) income, net	$ (4,395)	$ (881)		$ (6,344)
[1]	For the year ended December 31, 2017, income tax expense included income tax provisions of $4.5 million recognized as a result of new U.S. tax legislation signed into law on December 22, 2017.

Note 2 - Business Acquisition_2

Note 2 - Business Acquisitions (Details Textual) $ in Thousands	Feb. 08, 2018USD ($)	Apr. 28, 2017USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Cash Acquired from Acquisition				$ 1,943
Sea-cat Crewzer I and II [Member]
Cash Acquired from Acquisition				$ 5,900
Sea-Cat Crewzer [Member]
Business Acquisition, Percentage of Voting Interests Acquired		100.00%
Number of Equipment Operated		2	2
Equity Method Investment, Ownership Percentage		50.00%
Payments to Acquire Businesses, Gross		$ 4,400
Sea-Cat Crewzer II [Member]
Business Acquisition, Percentage of Voting Interests Acquired		100.00%
Number of Equipment Operated		2	2
Equity Method Investment, Ownership Percentage		50.00%
Payments to Acquire Businesses, Gross		$ 11,300
Falcon Global Holdings [Member]
Joint Venture, Total Capital	$ 112,500
Joint Venture, Contribution from Previous Joint Venture	43,300
Joint Venture, Contribution from Noncontrolling Interest	$ 18,800
Falcon Global Holdings [Member]
Noncontrolling Interest, Ownership Percentage by Parent	72.00%		72.00%
Business Acquisition, Percentage of Voting Interests Acquired		100.00%

Note 2 - Business Acquisition_3

Note 2 - Business Acquisitions - Allocation of the Purchase Price for the Company's Acquisitions (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Trade and other receivables			$ 235
Other current assets		211	4,148
Investments, at Equity, and Advances to 50% or Less Owned Companies			(15,700)
Property and Equipment		140,257	61,626
Accounts payable			747
Other current liabilities			(76)
Long-Term Debt		(106,640)	(41,186)
Other			(43)
Minority Interest		(18,828)
Purchase price (1)	[1]	$ 15,000	$ 9,751
[1]	Purchase price in 2018 was used to pay MOI's debtor-in-possession obligations. Purchase price in 2017 is net of cash acquired totaling $5.9 million.

Note 3 - Equipment Acquisitio_3

Note 3 - Equipment Acquisitions and Dispositions (Details Textual) $ in Millions	Sep. 13, 2018	Dec. 31, 2018USD ($)		Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Payments to Acquire Property, Plant and Equipment and Fair Value Derivative Hedges		$ 52		$ 69.4	$ 101.3
Number of Equipment Acquired		8	[1]	11	17
Proceeds from Sale of Property, Plant, and Equipment, Including Deposits		$ 18.6		$ 11.2	$ 41.4
Proceeds from Sale of Property, Plant, and Equipment, Excluding Deposits for Future Vessel Sales		18.5
Proceeds from Deposits		0.1
Gain (Loss) on Disposition of Property Plant Equipment, Total		5.9		3.9	3.5
Increase (Decrease) in Contract with Customer, Liability		$ 4.4		$ 0.1	$ 0.5
Number of Equipment Removed from Service		16	[2]	4	9
SEACOR Marlin LLC [Member]
Equity Method Investment, Ownership, Percent Sold	51.00%	51.00%
Anchor Handling Towing Supply [Member] | SEACOR 88/888 [Member]
Number of Equipment Acquired		2
Crew Transfer Vessels [Member]
Number of Equipment Acquired		2	[1]		2
Number of Equipment Sold		1
Number of Equipment Removed from Service		1	[2]
Crew Transfer Vessels [Member] | Windcat Offshore Logistics [Member]
Number of Equipment Acquired		1
Supply Vessels [Member]
Number of Equipment Sold		1
Number of Equipment Removed from Service		1
Offshore Support Vessels, Anchor Handling Towing Supply [Member]
Number of Equipment Acquired			[1]	5	2
Number of Equipment Removed from Service		1	[2]
Tow-supply Vessel [Member]
Number of Equipment Removed from Service		1
[1]	Excludes two AHTS vessels purchased from Managed Entity Seacor 88 and Seacor 888, and one crew transfer vessel purchased from the Company's joint venture FRS Windcat Offshore Logistics.
[2]	Excludes the sale of (i) a 51% interest in one supply vessel held by the joint venture Seacor Marlin LLC, (ii) one crew transfer vessel to the joint venture FRS Windcat Offshore Logistics and (iii) three vessels that were previously removed from service (one FSV, one tow-supply vessel and one supply vessel).

Note 3 - Equipment Acquisitio_4

Note 3 - Equipment Acquisitions and Dispositions - Equipment Acquisitions and Dispositions (Details)	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Acquired	8	[1]	11	17
Removed from service	16	[2]	4	9
Fast Support Vessels [Member]
Acquired		[1]	6	12
Removed from service	9	[2]
Offshore Support Vessels, Anchor Handling Towing Supply [Member]
Acquired		[1]	5	2
Removed from service	1	[2]
Offshore Support Vessels, Specialty [Member]
Acquired		[1]		1
Offshore Support Vessels, Standby Safety [Member]
Removed from service	3	[2]	1	4
Offshore Support Vessels, Liftboats [Member]
Acquired	6	[1]
Removed from service	2	[2]	2
Offshore Support Vessels, Supply [Member]
Removed from service		[2]	1	5
Crew Transfer Vessels [Member]
Acquired	2	[1]		2
Removed from service	1	[2]
[1]	Excludes two AHTS vessels purchased from Managed Entity Seacor 88 and Seacor 888, and one crew transfer vessel purchased from the Company's joint venture FRS Windcat Offshore Logistics.
[2]	Excludes the sale of (i) a 51% interest in one supply vessel held by the joint venture Seacor Marlin LLC, (ii) one crew transfer vessel to the joint venture FRS Windcat Offshore Logistics and (iii) three vessels that were previously removed from service (one FSV, one tow-supply vessel and one supply vessel).

Note 4 - Investments, at Equi_3

Note 4 - Investments, at Equity, and Advances to 50% or Less Owned Companies (Details Textual)	Dec. 28, 2018USD ($)	Dec. 20, 2018USD ($)	Sep. 28, 2018USD ($)	Sep. 13, 2018USD ($)	Jan. 17, 2018USD ($)	Apr. 28, 2017USD ($)	Sep. 30, 2018USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)		Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Equity Method Investment, Unrealized Intercompany Profit (Loss) Not Eliminated, Amount									$ 28,500,000		$ 46,100,000
Proceeds from Equity Method Investment, Distribution, Return of Capital									$ 16,263,000		$ 40,000
Number of Equipment Acquired									8	[1]	11	17
Payments to Acquire Property, Plant, and Equipment, Total									$ 51,980,000		$ 69,021,000	$ 100,884,000
Unrecorded Unconditional Purchase Obligation, Total									78,178,000
Proceeds from Divestiture of Interest in Joint Venture									8,017,000
Equity Method Investment, Other than Temporary Impairment									1,200,000		8,800,000	6,900,000
Income (Loss) from Equity Method Investments, Total									(3,415,000)		4,077,000	(6,314,000)
Equity Method Investments									121,773,000		92,169,000
Repayment of Notes Receivable from Related Parties									116,000
MEXMAR Offshore [Member]
Partners' Capital Account, Contributions		$ 10,000,000
Noncontrolling Interest, Ownership Percentage by Parent		49.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		51.00%
Offshore Vessel Holdings [Member]
Noncontrolling Interest, Ownership Percentage by Parent	49.00%
Payments to Acquire Interest in Joint Venture	$ 4,900,000
Offshore Support Vessels, Supply [Member]
Number of Equipment Operated		11
ROV Support Vessels [Member]
Number of Equipment Operated		2
Offshore Terminal Vessel [Member]
Number of Equipment Operated		1
MexMar [Member]
Proceeds from Equity Method Investment, Distribution, Return of Capital									9,800,000		7,400,000
Partners' Capital Account, Contributions												$ 7,400,000
Number of Equipment Acquired												2
Payments to Acquire Machinery and Equipment												$ 34,000,000
Revenue from Related Parties									$ 300,000		300,000	300,000
Related Party Transaction, Expenses from Transactions with Related Party												5,100,000
Equity Method Investment, Ownership Percentage									49.00%
Income (Loss) from Equity Method Investments, Total									$ 2,736,000		10,103,000	3,556,000
Equity Method Investments									$ 53,840,000		60,980,000
MexMar [Member] | Offshore Support Vessels [Member]
Number of Equipment Operated									16
SeaCosco Offshore LLC [Member]
Number of Equipment Operated					8
Partners' Capital Account, Contributions									$ 29,600,000
Payments to Acquire Property, Plant, and Equipment, Total					$ 163,300,000
Equity Method Investment, Ownership Percentage					50.00%				50.00%
Unrecorded Unconditional Purchase Obligation, Total									$ 2,000,000
Equity Method Investments									28,002,000
OSV Partners [Member]
Partners' Capital Account, Contributions											2,300,000	1,200,000
Revenue from Related Parties									$ 600,000		600,000	500,000
Equity Method Investment, Ownership Percentage									30.40%
Investment in Affiliates, Amount of Preferred Equity Offereing Participated			$ 5,000,000
Payments to Acquire Interest in Subsidiaries and Affiliates, Total			1,100,000
Commitment to Invest Additional Funds if Call By General Partner			1,100,000
Payments to Acquire Loans Receivable			2,100,000
Equity Method Investments									$ 11,087,000		10,006,000
OSV Partners [Member] | General Partner [Member]
Partners' Capital Account, Contributions			$ 5,000,000								6,000,000
Equity Method Investment, Ownership Percentage									38.60%
OSV Partners [Member] | Offshore Support Vessels [Member]
Number of Equipment Operated									5
SEACOR Marlin LLC [Member]
Equity Method Investment, Ownership Percentage									49.00%
Equity Method Investment, Ownership, Percent Sold				51.00%					51.00%
Proceeds from Divestiture of Interest in Joint Venture				$ 8,000,000
Gain (Loss) on Disposition of Business				$ 400,000
Equity Method Investments									$ 7,579,000
MEXMAR Offshore [Member]
Number of Equipment Operated		14
Equity Method Investment, Ownership Percentage									49.00%
Equity Method Investments									$ 4,900,000
MEXMAR Offshore [Member] | BRAZIL
Number of Equipment Operated		12
MEXMAR Offshore [Member] | UNITED KINGDOM
Number of Equipment Operated		2
Dynamic Offshore [Member]
Equity Method Investment, Ownership Percentage									19.00%
Equity Method Investment, Other than Temporary Impairment											8,300,000
Income (Loss) from Equity Method Investments, Total									$ (2,700,000)
Equity Method Investments									$ 2,263,000		4,958,000
Nautical Power [Member]
Equity Method Investment, Ownership Percentage									50.00%
Proceeds from Divestiture of Interest in Joint Venture							$ 6,400,000
Equity Method Investments											6,408,000
Falcon Global [Member]
Partners' Capital Account, Contributions								$ 400,000
Payments for Advance to Affiliate								$ 2
Business Acquisition, Percentage of Voting Interests Acquired								100.00%
Falcon Global [Member] | Liftboats [Member]
Number of Equipment Operated									2
Sea-Cat Crewzer II [Member]
Number of Equipment Operated						2			2
Equity Method Investment, Ownership Percentage						50.00%
Business Acquisition, Percentage of Voting Interests Acquired						100.00%
Payments to Acquire Businesses, Gross						$ 11,300,000
Sea-Cat Crewzer [Member]
Number of Equipment Operated						2			2
Equity Method Investment, Ownership Percentage						50.00%
Business Acquisition, Percentage of Voting Interests Acquired						100.00%
Payments to Acquire Businesses, Gross						$ 4,400,000
Other Offshore Marine Services Joint Ventures [Member]
Number of Equipment Operated									8
Proceeds from Equity Method Investment, Distribution, Return of Capital									$ 1,700,000		2,600,000	800,000
Partners' Capital Account, Contributions											800,000	500,000
Revenue from Related Parties									300,000		700,000	800,000
Equity Method Investment, Other than Temporary Impairment									1,200,000		500,000	500,000
Income (Loss) from Equity Method Investments, Total									(6,151,000)		(6,026,000)	(9,870,000)
Equity Method Investments									9,202,000		9,817,000
Repayment of Notes Receivable from Related Parties											$ 200,000
Allocable Share of Uncalled Capital									800,000
Guarantee of Outstanding Charter Receivables									$ 300,000
Other Offshore Marine Services Joint Ventures [Member] | Offshore Support Vessels [Member]
Asset Impairment Charges, Total												$ 2,700,000
[1]	Excludes two AHTS vessels purchased from Managed Entity Seacor 88 and Seacor 888, and one crew transfer vessel purchased from the Company's joint venture FRS Windcat Offshore Logistics.

Note 4 - Investments, at Equi_4

Note 4 - Investments, at Equity, and Advances to 50% or Less Owned Companies - Equity Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 17, 2018
Investments at equity	$ 121,773	$ 92,169
MexMar [Member]
Ownership percentage	49.00%
Investments at equity	$ 53,840	60,980
Current assets	38,113	71,990
Noncurrent assets	215,207	194,990
Current liabilities	27,610	23,931
Noncurrent liabilities	115,948	147,043
Operating Revenues	57,003	67,003	$ 70,521
Operating and administrative	25,932	29,405	37,613
Depreciation	16,295	15,977	13,958
	42,227	45,382	51,571
Operating Income	14,776	21,621	18,950
Net Income	5,584	9,233	6,476
All Other Excluding MexMar, Falcon Global, Sea-Cat Crewzer and Sea-Cat Crewzer II [Member]
Current assets	61,287	61,360
Noncurrent assets	352,421	247,038
Current liabilities	32,302	14,603
Noncurrent liabilities	209,752	138,789
Operating Revenues	54,853	77,409	77,571
Operating and administrative	53,967	46,748	51,136
Depreciation	10,148	12,198	13,181
	64,115	58,946	64,317
Operating Income	(9,351)	18,463	(8,069)
Net Income	(20,383)	6,451	(19,229)
Loss on Asset Dispositions and Impairments, Net	$ (89)		(21,323)
SeaCosco Offshore LLC [Member]
Ownership percentage	50.00%			50.00%
Investments at equity	$ 28,002
OSV Partners [Member]
Ownership percentage	30.40%
Investments at equity	$ 11,087	10,006
SEACOR Marlin LLC [Member]
Ownership percentage	49.00%
Investments at equity	$ 7,579
MEXMAR Offshore [Member]
Ownership percentage	49.00%
Investments at equity	$ 4,900
Offshore Vessel Holdings [Member]
Ownership percentage	49.00%
Investments at equity	$ 4,900
Dynamic Offshore [Member]
Ownership percentage	19.00%
Investments at equity	$ 2,263	4,958
Nautical Power [Member]
Ownership percentage	50.00%
Investments at equity		6,408
Other Offshore Marine Services Joint Ventures [Member]
Investments at equity	$ 9,202	9,817
Other Offshore Marine Services Joint Ventures [Member] | Minimum [Member]
Ownership percentage	20.00%
Other Offshore Marine Services Joint Ventures [Member] | Maximum [Member]
Ownership percentage	50.00%
Falcon Global, Sea-Cat Crewzer and Sea-Cat Crewzer II [Member]
Operating Revenues		5,075	21,611
Operating and administrative		3,752	12,837
Depreciation		2,324	3,694
		6,076	16,531
Operating Income		(1,001)	5,080
Net Income		$ (2,699)	$ 778

Note 4 - Investments, at Equi_5

Note 4 - Investments, at Equity, and Advances to 50% or Less Owned Companies - Consolidation Net Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Trade and other receivables		$ 235
Investments, at Equity, and Advances to 50% or Less Owned Companies		15,700
Property and Equipment	140,257	61,626
Accounts payable		747
Other current liabilities		76
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	106,640	41,186
Other Liabilities		43
Noncontrolling interests in subsidiaries	$ 29,404	$ 14,975
Falcon Global [Member] | Segment Reconciling Items [Member]
Cash			$ 1,943
Marketable securities			785
Trade and other receivables			(291)
Investments, at Equity, and Advances to 50% or Less Owned Companies			(19,374)
Property and Equipment			96,000
Accounts payable			3,201
Other current liabilities			1,153
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt			58,335
Other Liabilities			(1,000)
Noncontrolling interests in subsidiaries			$ 17,374

Note 5 - Construction Reserve_3

Note 5 - Construction Reserve Funds - Construction Reserve Funds (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Withdrawals	$ (17,300)	$ (39,163)	$ (87,820)
Deposits		6,315	27,414
	$ (17,300)	$ (32,848)	$ (60,406)

Note 6 - Leases (Details Textua

Note 6 - Leases (Details Textual) $ in Thousands	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Number of Vessels Leased		8
Operating Leases, Rent Expense, Net, Total		$ 13,300	$ 14,500	$ 19,400
Operating Lease, Impairment Loss		$ 6,800	$ 5,400
Number of Operating Leases Impaired		3	1
Subsequent Event [Member] | Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset	$ 33,900
Operating Lease, Liability, Total	32,100
Subsequent Event [Member] | Accounting Standards Update 2016-02 [Member] | Change in Accounting Principle for Equipment, Office and Land Leases [Member]
Cumulative Effect on Retained Earnings, Net of Tax, Total	1,800
Subsequent Event [Member] | Accounting Standards Update 2016-02 [Member] | Change in Accounting Principle for Unamortized Deferred Gains [Member]
Cumulative Effect on Retained Earnings, Net of Tax, Total	$ 8,700
Minimum [Member]
Lessee, Operating Lease, Term of Contract		1 year
Maximum [Member]
Lessee, Operating Lease, Term of Contract		3 years

Note 6 - Leases - Schedule of F

Note 6 - Leases - Schedule of Future Minimum Rental Payments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
2019	$ 14,288
2020	13,826
2021	6,480
2022	331
2023 and beyond	$ 661

Note 7 - Long-term Debt (Detail

Note 7 - Long-term Debt (Details Textual) $ / shares in Units, € in Millions	Sep. 28, 2018USD ($)	Sep. 26, 2018USD ($)	May 02, 2018USD ($)$ / sharesshares	Feb. 08, 2018USD ($)	Nov. 03, 2017USD ($)	Apr. 28, 2017USD ($)	Dec. 12, 2016USD ($)	Dec. 31, 2017USD ($)	Dec. 12, 2016USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2018EUR (€)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2016EUR (€)	Oct. 31, 2018USD ($)	Sep. 30, 2018$ / shares	Jul. 05, 2018USD ($)	Mar. 31, 2017USD ($)	May 24, 2016EUR (€)	Apr. 21, 2016EUR (€)	Dec. 01, 2015USD ($)	Aug. 03, 2015USD ($)
Debt Instrument, Increase (Decrease), Net, Total		$ 30,100,000								$ 1,000,000
Gain (Loss) on Extinguishment of Debt, Total										(638,000)
Debt Instrument, Unamortized Discount, Total								$ 27,373,000		32,005,000		27,373,000
Repayments of Long-term Debt, Total										49,405,000		11,926,000	27,152,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt								$ 41,186,000		106,640,000		$ 41,186,000
Long-term Debt Obligation [Member]
Letters of Credit Outstanding, Amount										$ 2,800,000
Falcon Global [Member]
Business Acquisition, Percentage of Voting Interests Acquired																		100.00%
Sea-Cat Crewzer II [Member]
Business Acquisition, Percentage of Voting Interests Acquired						100.00%
Equity Method Investment, Ownership Percentage						50.00%
Payments to Acquire Businesses, Gross						$ 11,300,000
Sea-Cat Crewzer [Member]
Debt Instrument, Interest Rate, Stated Percentage								1.52%				1.52%
Payments of Debt Issuance Costs												$ 100,000
Business Acquisition, Percentage of Voting Interests Acquired						100.00%
Equity Method Investment, Ownership Percentage						50.00%
Debt Instrument, Final Baloon Payment								$ 15,300,000				$ 15,300,000
Payments to Acquire Businesses, Gross						$ 4,400,000
C-Lift [Member]
Business Acquisition, Percentage of Voting Interests Acquired								50.00%				50.00%
Cypress CKOR LLC [Member]
Equity Method Investment, Ownership Percentage							100.00%		100.00%
Payments to Acquire Businesses, Gross							$ 1
Minimum [Member] | Sea-Cat Crewzer [Member]
Debt Instrument, Basis Spread on Variable Rate												2.10%
Maximum [Member] | Sea-Cat Crewzer [Member]
Debt Instrument, Basis Spread on Variable Rate												2.75%
Falcon Global Holdings [Member]
Noncontrolling Interest, Ownership Percentage by Parent				72.00%						72.00%
Business Acquisition, Percentage of Voting Interests Acquired						100.00%
Falcon Global USA LLC [Member]
Payments for Debtor-in-possession Obligations				$ 15,000,000
Convertible Senior Notes Converted to Warrants [Member] | Carlyle Group [Member]
Debt Instrument, Convertible, Conversion Ratio			37.73
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares			$ 0.01
Debt Conversion, Original Debt, Amount			$ 50,000,000
Debt Conversion, Converted Instrument, Shares Issued | shares			1,886,792
Debt Instrument, Convertible, Conversion Price | $ / shares			$ 26.50
Conversion Revolving Credit Facility from Windcat Workboats [Member]
Debt Conversion, Original Debt, Amount | €											€ 6
Carlyle Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares																$ 0.01
Warrants and Rights Outstanding, Term			25 years
Loan Facility With DNB Bank ASA [Member]
Line of Credit Facility, Maximum Borrowing Capacity		$ 130,000,000
Debt Instrument, Interest Rate, Effective Percentage		6.5625%
Debt Instrument, Periodic Payment, Principal		$ 3,300,000
Loan Facility With DNB Bank ASA [Member] | Interest Rate Swap [Member]
Derivative, Notional Amount															$ 65,000,000
Other DNB Credit Facilities [Member]
Repayments of Lines of Credit		101,300,000
Long-term Debt, Total		99,900,000
Interest Payable		1,400,000
Gain (Loss) on Extinguishment of Debt, Total		$ 600,000
Convertible Senior Notes 3.75% [Member]
Convertible Debt, Total			$ 125,000,000																		$ 175,000,000
Debt Instrument, Interest Rate, Stated Percentage			4.25%																		3.75%
Debt Instrument, Convertible, Conversion Ratio										23.26	23.26
Three Point Seven Five Percentage Convertible Notes [Member]
Debt Instrument, Interest Rate, Effective Percentage										7.95%
Embedded Derivative, Fair Value of Embedded Derivative Liability																					$ 27,300,000
FGUSA Credit Facility [Member]
Debt Agreement, Maximum Borrowing Capacity				131,100,000
Debt Instrument, Unamortized Discount, Total				10,000,000
FGUSA Credit Facility [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity				15,000,000
Debt Instrument, Interest Rate, Effective Percentage										7.0625%
Debt Instrument, Unamortized Discount, Total				500,000
Proceeds from Lines of Credit, Total										$ 15,000,000
FGUSA Credit Facility [Member] | Term Loan [Member]
Long-term Debt, Total				116,100,000
Debt Instrument, Periodic Payment, Principal										7,000,000
Debt Instrument, Unamortized Discount, Total				$ 9,500,000
Sea-Cat Crewzer III [Member]
Debt Instrument, Interest Rate, Effective Percentage								2.76%				2.76%
Debt Instrument, Face Amount | €																				€ 27.6
Proceeds from Issuance of Debt												$ 7,100,000	22,800,000
Debt Issuance Costs, Gross													2,700,000
Repayments of Long-term Debt, Total										3,100,000		600,000
Windcat Workboats Ltd. [Member]
Line of Credit Facility, Maximum Borrowing Capacity | €																			€ 25
Proceeds from Lines of Credit, Total													23,500,000	€ 21
Debt Issuance Costs, Gross													600,000
Repayments of Long-term Debt, Total													$ 22,900,000
Windcat Workboats Ltd. [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate													3.00%	3.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage													1.20%	1.20%
Windcat Workboats Ltd. [Member] | Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate													3.30%	3.30%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage													1.32%	1.32%
Euro Debt [Member]
Repayments of Long-term Debt, Total										7,500,000
Pound Sterling Debt [Member]
Proceeds from Issuance of Long-term Debt, Total										$ 8,500,000
Term Loan to Acquire Two Vessels [Member]
Debt Instrument, Interest Rate, Effective Percentage																	5.9375%
Debt Instrument, Face Amount																	$ 11,000,000
Term Loan to Acquire Two Vessels [Member] | Interest Rate Swap [Member]
Derivative, Notional Amount															$ 5,500,000
BNDES [Member]
Debt Instrument, Interest Rate, Effective Percentage										4.00%
Repayments of Long-term Debt, Total										$ 2,000,000		$ 2,000,000	$ 2,000,000
Tranche A [Member] | Falcon Global [Member]
Debt Instrument, Face Amount																						$ 62,500,000
Tranche B [Member] | Falcon Global [Member]
Debt Instrument, Face Amount																						$ 18,000,000
Falcon Global [Member]
Debt Issuance Costs, Gross																		$ 1,000,000
Repayments of Long-term Debt, Total	$ 51,900,000							$ 4,400,000		3,000,000
Payments of Debt Issuance Costs					$ 200,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt																		$ 58,300,000
Sea-Cat Crewzer II [Member]
Debt Instrument, Interest Rate, Effective Percentage								5.64%				5.64%
Debt Instrument, Interest Rate, Stated Percentage								1.52%				1.52%
Repayments of Long-term Debt, Total	19,100,000									1,800,000		$ 1,200,000
Payments of Debt Issuance Costs												100,000
Debt Instrument, Final Baloon Payment								$ 17,300,000				$ 17,300,000
Sea-Cat Crewzer II [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate												2.10%
Sea-Cat Crewzer II [Member] | Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate												2.75%
Sea-Cat Crewzer [Member]
Debt Instrument, Interest Rate, Effective Percentage								5.64%				5.64%
Repayments of Long-term Debt, Total	16,900,000									1,600,000		$ 1,100,000
C-Lift [Member]
Repayments of Long-term Debt, Total	$ 12,000,000									4,000,000		1,500,000	$ 1,700,000
Payments of Debt Issuance Costs												100,000
Cypress CKOR LLC [Member]
Repayments of Long-term Debt, Total									$ 600,000	$ 1,300,000		$ 1,200,000
Secured Long-term Debt, Noncurrent							$ 3,100,000		$ 3,100,000

Note 7 - Long-term Debt - Sched

Note 7 - Long-term Debt - Schedule of long-term Debt Obligation (Details) - USD ($)	Dec. 31, 2018	Feb. 08, 2018	Dec. 31, 2017
Long-term Debt, Gross	$ 442,972,000		$ 348,059,000
	442,972,000		348,059,000
Portion due within one year	(16,812,000)		(22,858,000)
Debt discount	(32,005,000)		(27,373,000)
Issue costs	(6,301,000)		(5,787,000)
	387,854,000		292,041,000
Loan Facility With DNB Bank ASA [Member]
Long-term Debt, Gross	126,750,000
	126,750,000
Three Point Seven Five Percentage Convertible Notes [Member]
Long-term Debt, Gross	125,000,000		175,000,000
	125,000,000		175,000,000
Falcon Global Holdings [Member]
Long-term Debt, Gross	109,099,000
	109,099,000
Sea-Cat Crewzer III [Member]
Long-term Debt, Gross	25,989,000		29,078,000
	25,989,000		29,078,000
Windcat Workboats Ltd. [Member]
Long-term Debt, Gross	24,850,000		25,202,000
	24,850,000		25,202,000
FGUSA Credit Facility [Member]
Long-term Debt, Gross	15,000,000
	15,000,000
Debt discount		$ (10,000,000)
Term Loan to Acquire Two Vessels [Member]
Long-term Debt, Gross	11,000,000
	11,000,000
BNDES [Member]
Long-term Debt, Gross	5,284,000		7,234,000
	5,284,000		7,234,000
Falcon Global [Member]
Long-term Debt, Gross			54,870,000
			54,870,000
Sea-Cat Crewzer II [Member]
Long-term Debt, Gross			20,871,000
			20,871,000
Sea-Cat Crewzer [Member]
Long-term Debt, Gross			18,504,000
			18,504,000
C-Lift [Member]
Long-term Debt, Gross			16,000,000
			16,000,000
Cypress CKOR LLC [Member]
Long-term Debt, Gross			1,300,000
			$ 1,300,000

Note 7 - Long-term Debt - Sch_2

Note 7 - Long-term Debt - Schedule of Long-term Debt Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
2019	$ 16,812
2020	25,489
2021	51,381
2022	25,150
2023	222,900
Years subsequent to 2023	101,240
	$ 442,972	$ 348,059

Note 8 - Income Taxes (Details

Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%	35.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability		$ (3,900)
Increase (Decrease) in Transition Tax Liability		$ 3,400
Current Income Tax Expense (Benefit), Nonqualified Withdrwal of Funds from Capital Construction Fund	$ 1,400
Effective Income Tax Rate Reconciliation, Percent, Total	14.50%	63.60%	(33.40%)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount		$ 4,500
Interest Expense Suspended	$ 7,300
Interest Expense Suspended, Limitation Percentage	30.00%
Operating Loss Carryforwards, Percentage of Taxable Income, Utilization Limitation	80.00%
Operating Loss Carryforwards, Total	$ 57,600	$ 42,200
Operating Loss Carryforwards, Expiration Period		20 years
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Valuation Allowance, Total	$ 600	$ 600

Note 8 - Income Taxes - Schedul

Note 8 - Income Taxes - Schedule of Income before Income Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Before Income Tax Expense (Benefit) and Equity in Earnings of 50% or Less Owned Companies	$ (91,984)	$ (117,023)	$ (190,305)
Domestic Tax Authority [Member]
Income Before Income Tax Expense (Benefit) and Equity in Earnings of 50% or Less Owned Companies	(72,540)	(90,696)	(169,523)
Foreign Tax Authority [Member]
Income Before Income Tax Expense (Benefit) and Equity in Earnings of 50% or Less Owned Companies	(28,226)	(45,112)	(28,095)
Eliminations [Member]
Income Before Income Tax Expense (Benefit) and Equity in Earnings of 50% or Less Owned Companies	$ 8,782	$ 18,785	$ 7,313

Note 8 - Income Taxes - Compone

Note 8 - Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Federal, Current	$ 5,987	$ (16,705)	$ (20,718)
State, Current	3	(42)	(139)
Foreign, Current	3,400	3,347	5,436
Current Income Tax Expense	9,390	(13,400)	(15,421)
Federal, deferred	(21,466)	(60,750)	(47,692)
State, deferred	(1,404)	(172)	(446)
Foreign, deferred	133	(84)	90
Deferred Income Tax Benefit	(22,737)	(61,006)	(48,048)
Income Tax Benefit	$ (13,347)	$ (74,406)	$ (63,469)

Note 8 - Income Taxes - Income

Note 8 - Income Taxes - Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statutory rate	(21.00%)	(35.00%)	(35.00%)
U.S. federal income tax law changes		(37.30%)
SEACOR Holdings share awards to Company personnel	0.20%	2.30%	0.40%
Non-deductible expenses		1.80%	0.10%
Exclusion of foreign subsidiaries with accumulated losses and withholding tax	9.30%	2.70%	1.10%
Noncontrolling interests	(1.50%)	1.70%	0.20%
State taxes	(1.50%)	(0.20%)	(0.30%)
Other	0.00%	0.40%	0.10%
	14.50%	63.60%	(33.40%)

Note 8 - Income Taxes - Sched_2

Note 8 - Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property and equipment	$ 65,880	$ 55,262
Investments in 50% or Less Owned Companies	3,040	4,258
Other	7,789	5,901
Total deferred tax liabilities	76,709	65,421
Federal Net Operating Loss Carryforwards	20,974	5,111
Other	11,677	5,373
Total deferred tax assets	32,651	10,484
Valuation Allowance	(624)	(569)
Total deferred tax assets	32,027	9,915
Net deferred tax liabilities	$ 44,682	$ 55,506

Note 9 - Derivative Instrumen_3

Note 9 - Derivative Instruments and Hedging Strategies (Details Textual) $ in Thousands, € in Millions	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2018EUR (€)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	$ 1,939	$ (214)	$ 2,493
Derivative, Fair Value, Net, Total	6,900
Interest Rate Swap [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	$ (1,939)	214	(2,493)
Interest Rate Swap [Member] | OSV Partners [Member]
Derivative, Number of Instruments Held, Total	2			2
Derivative, Notional Amount	$ 27,900
Interest Rate Swap [Member] | OSV Partners [Member] | Minimum [Member]
Derivative, Fixed Interest Rate	1.89%			1.89%
Interest Rate Swap [Member] | OSV Partners [Member] | Maximum [Member]
Derivative, Fixed Interest Rate	2.27%			2.27%
Cash Flow Hedging [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	$ (1,600)	200	(2,500)
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative, Number of Instruments Held, Total	2			2
Derivative, Fixed Interest Rate	0.03%			0.03%
Derivative, Notional Amount	$ 17,200			€ 15
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | SEACOR Marine Foreign Holdings [Member]
Derivative, Fixed Interest Rate	3.32%			3.32%
Derivative, Notional Amount	$ 9,800
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | SEACOR 88/888 [Member]
Derivative, Fixed Interest Rate	3.50%			3.50%
Derivative, Notional Amount	$ 5,500
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | MexMar [Member]
Derivative, Number of Instruments Held, Total	5			5
Derivative, Notional Amount	$ 97,000
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | MexMar [Member] | Minimum [Member]
Derivative, Fixed Interest Rate	1.71%			1.71%
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | MexMar [Member] | Maximum [Member]
Derivative, Fixed Interest Rate	2.10%			2.10%
Cash Flow Hedging [Member] | Interest Rate Swap 2 [Member] | Designated as Hedging Instrument [Member] | SEACOR Marine Foreign Holdings [Member]
Derivative, Fixed Interest Rate	3.195%			3.195%
Derivative, Notional Amount	$ 54,100
Construction in Progress [Member] | Fair Value Hedging [Member]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge		$ 100	$ (800)

Note 9 - Derivative Instrumen_4

Note 9 - Derivative Instruments and Hedging Strategies - Derivative Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivative instruments (included in other receivables)		$ 419
Derivative Liability	6,935	6,898
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative instruments (included in other receivables)		260
Derivative Liability	1,659	20
Not Designated as Hedging Instrument [Member] | Non-current Liabilities [Member]
Conversion option liability on Convertible Senior Notes	5,276	6,832
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Current Assets [Member]
Derivative instruments (included in other receivables)		260
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Current Liabilities [member]
Derivative Liability	1,659	20
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member] | Current Assets [Member]
Derivative instruments (included in other receivables)		159
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member] | Current Liabilities [member]
Derivative Liability		$ 46

Note 9 - Derivative Instrumen_5

Note 9 - Derivative Instruments and Hedging Strategies - Effect of Derivative Instruments on Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	$ 1,939	$ (214)	$ 2,493
Interest Expense [Member]
Gain (Loss) Reclassified from OCI into Income (Effective Portion)	31	118	18
Interest Rate Swap [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	(1,939)	214	(2,493)
Joint Venture Interest Rate Swap [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	$ (76)	$ 389	$ 2,744

Note 9 - Derivative Instrumen_6

Note 9 - Derivative Instruments and Hedging Strategies - Gains (Losses) on Derivative Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Gains (losses) on derivative instruments	$ 2,855	$ 20,256	$ 2,995
Embedded Derivative Financial Instruments [Member]
Gains (losses) on derivative instruments	1,556	20,422
Interest Rate Swap [Member]
Gains (losses) on derivative instruments	1,298	46	(18)
Equity Option [Member]
Gains (losses) on derivative instruments			3,095
Foreign Exchange Option [Member]
Gains (losses) on derivative instruments		$ (212)	$ (82)

Note 10 - Fair Value Measurem_3

Note 10 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative, Gain (Loss) on Derivative, Net, Total	$ 1,600
Impairment of Long-Lived Assets Held-for-use	$ 14,600	$ 27,500	$ 119,700

Note 10 - Fair Value Measurem_4

Note 10 - Fair Value Measurements - Assets and Liabilities on Recurring Basis (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Derivative Liability		$ 6,935	$ 6,898
Derivative instruments (included in other receivables)			419
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Construction reserve funds		28,221	45,361
Derivative Liability
Exchange Option Liability on Subsidiary Convertible Senior Notes
Derivative instruments (included in other receivables)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Construction reserve funds
Derivative Liability		1,659	66
Exchange Option Liability on Subsidiary Convertible Senior Notes
Derivative instruments (included in other receivables)			419
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Construction reserve funds	[1]
Derivative Liability	[1]
Exchange Option Liability on Subsidiary Convertible Senior Notes	[1]	$ 5,276	6,832
Derivative instruments (included in other receivables)	[1]
[1]	For the year ended December 31, 2018, the Company recognized a $1.6 million gain in the fair market valuation of the Convertible Senior Notes, as valued by an independent third-party.

Note 10 - Fair Value Measurem_5

Note 10 - Fair Value Measurements - Estimated Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Reported Value Measurement [Member]
Cash, cash equivalents and restricted cash	$ 96,852	$ 112,551
Investments, at cost, in 50% or less owned companies (included in other assets)	132	132
Long-term debt, including current portion	404,666	314,899
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash, cash equivalents and restricted cash	96,852	112,551
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash, cash equivalents and restricted cash
Investments, at cost, in 50% or less owned companies (included in other assets)
Long-term debt, including current portion	388,949	291,932
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash, cash equivalents and restricted cash
Investments, at cost, in 50% or less owned companies (included in other assets)
Long-term debt, including current portion

Note 10 - Fair Value Measurem_6

Note 10 - Fair Value Measurements - Other Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Inputs, Level 1 [Member]
Equity Method Investments, Fair Value Disclosure
Fair Value, Inputs, Level 1 [Member] | Anchor Handling Towing Supply [Member]
Property and equipment, Fair Value Disclosure
Property and equipment, Fair Value Disclosure
Fair Value, Inputs, Level 1 [Member] | Liftboats [Member]
Property and equipment, Fair Value Disclosure
Property and equipment, Fair Value Disclosure
Fair Value, Inputs, Level 1 [Member] | Offshore Support Vessels, Specialty [Member]
Property and equipment, Fair Value Disclosure
Property and equipment, Fair Value Disclosure
Fair Value, Inputs, Level 2 [Member]
Equity Method Investments, Fair Value Disclosure		20,658
Fair Value, Inputs, Level 2 [Member] | Anchor Handling Towing Supply [Member]
Property and equipment, Fair Value Disclosure	2,000	12,400
Property and equipment, Fair Value Disclosure	2,000	12,400
Fair Value, Inputs, Level 2 [Member] | Liftboats [Member]
Property and equipment, Fair Value Disclosure		175
Property and equipment, Fair Value Disclosure		175
Fair Value, Inputs, Level 2 [Member] | Offshore Support Vessels, Specialty [Member]
Property and equipment, Fair Value Disclosure	4,500	750
Property and equipment, Fair Value Disclosure	4,500	750
Fair Value, Inputs, Level 3 [Member]
Equity Method Investments, Fair Value Disclosure		20,430
Fair Value, Inputs, Level 3 [Member] | Anchor Handling Towing Supply [Member]
Property and equipment, Fair Value Disclosure
Property and equipment, Fair Value Disclosure
Fair Value, Inputs, Level 3 [Member] | Liftboats [Member]
Property and equipment, Fair Value Disclosure	134,775
Property and equipment, Fair Value Disclosure	134,775
Fair Value, Inputs, Level 3 [Member] | Offshore Support Vessels, Specialty [Member]
Property and equipment, Fair Value Disclosure
Property and equipment, Fair Value Disclosure

Note 11 - Warrants (Details Tex

Note 11 - Warrants (Details Textual) - USD ($)	Jun. 08, 2018	May 31, 2018	May 02, 2018	Apr. 26, 2018	Dec. 31, 2018
Stock Issued During Period, Value, New Issues					$ 42,996,000
Class of Warrant or Right, Exercised During Period	38,857	250,693
Class of Warrant or Right, Exercised During Period, Exercise Price	$ 0.01	$ 0.01
Carlyle Group [Member] | Convertible Senior Notes Converted to Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights			$ 0.01
Debt Conversion, Original Debt, Amount			$ 50,000,000
Warrants Issued in Private Placement [Member]
Class of Warrant or Right, Outstanding				2,168,586
Class of Warrant or Right, Number of Securities Called by Warrants or Rights				674,164
Class of Warrant or Right, Exercise Price of Warrants or Rights				$ 0.01
PIPE Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 0.01
Warrants and Rights Outstanding, Term				25 years
Exchange Warrants [Member]
Class of Warrant or Right, Outstanding					2,271,406
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 0.01
Warrants and Rights Outstanding, Term			25 years
Class of Warrant or Right, Exercised During Period	38,857	250,693
Class of Warrant or Right, Exercised During Period, Exercise Price	$ 0.01	$ 0.01
Exchange Warrants [Member] | Carlyle Group [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights			1,886,292
Private Placement [Member]
Stock Issued During Period, Value, New Issues				$ 56,855,000

Note 12 - Stockholders' Equity

Note 12 - Stockholders' Equity (Details Textual) - USD ($)	Jun. 08, 2018	May 31, 2018	May 02, 2018	Apr. 26, 2018	Mar. 26, 2018	Feb. 08, 2018	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Cumulative Effect of New Accounting Principle in Period of Adoption									$ (12,069,000)
Debt Instrument, Unamortized Discount, Total							$ 32,005,000		27,373,000
Adjustment to Stockholders Equity Due to Unamortized Debt Discount						$ 400,000
Stock Issued During Period, Shares, New Issues					103,213
Proceeds from Issuance of Private Placement					$ 1,800,000
Stock Issued During Period, Value, New Issues							$ 42,996,000
Class of Warrant or Right, Exercised During Period	38,857	250,693
Class of Warrant or Right, Exercised During Period, Exercise Price	$ 0.01	$ 0.01
Common Stock Held in Treasury in Exchange for Payment of Warrants Converted							108
Carlyle Group [Member] | Convertible Senior Notes Converted to Warrants [Member]
Debt Conversion, Original Debt, Amount			$ 50,000,000
Private Placement [Member]
Stock Issued During Period, Value, New Issues				$ 56,855,000
FGUSA Credit Facility [Member]
Debt Agreement, Maximum Borrowing Capacity						131,100,000
Debt Instrument, Unamortized Discount, Total						10,000,000
FGUSA Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument, Unamortized Discount, Total						500,000
FGUSA Credit Facility [Member] | Term Loan [Member]
Debt Instrument, Unamortized Discount, Total						9,500,000
Falcon Global USA LLC [Member]
Payments for Debtor-in-possession Obligations						$ 15,000,000
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption								$ (12,100,000)	$ (12,069,000)
Stock Issued During Period, Value, New Issues

Note 13 - Noncontrolling Inte_3

Note 13 - Noncontrolling Interests in Subsidiaries (Details Textual) - USD ($) $ in Thousands	Feb. 08, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Apr. 28, 2017
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total		$ (31,688)	$ (26,629)	$ (15,766)	$ (7,969)	$ (7,599)	$ (36,489)	$ (22,356)	$ 27,904	$ (82,052)	$ (38,540)	$ (133,150)
Net Income (Loss) Attributable to Noncontrolling Interest, Total										(4,444)	$ (5,639)	(1,103)
Windcat Workboats [Member]
Business Acquisition, Percentage of Voting Interests Acquired						12.50%					12.50%
Payments to Acquire Businesses, Gross											$ 3,700
Falcon Global Holdings [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	72.00%
Business Acquisition, Percentage of Voting Interests Acquired													100.00%
Falcon Global Holdings [Member]
Joint Venture, Total Capital	$ 112,500
Joint Venture, Contribution from Previous Joint Venture	43,300
Joint Venture, Contribution from Noncontrolling Interest	18,800
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	$ 14,300
Net Income (Loss) Attributable to Noncontrolling Interest, Total										4,000
Net Assets, Ending Balance		98,100								98,100
Windcat Workboats [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total										(3,100)	(2,100)	(4,500)
Net Income (Loss) Attributable to Noncontrolling Interest, Total										(400)	(400)	$ (1,100)
Net Assets, Ending Balance		$ 16,900				$ 21,100				$ 16,900	$ 21,100

Note 13 - Noncontrolling Inte_4

Note 13 - Noncontrolling Interests in Subsidiaries - Noncontrolling Interest (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Noncontrolling interest	$ 29,404	$ 14,975
Falcon Global [Member]
Noncontrolling interest percent	28.00%
Noncontrolling interest	$ 26,989	12,087
Windcat Workboats [Member]
Noncontrolling interest percent	12.50%
Noncontrolling interest	$ 2,115	2,608
Other Noncontrolling Interests [Member]
Noncontrolling interest percent	1.80%
Noncontrolling interest	$ 300	$ 280

Note 14 - Savings and Multi-e_2

Note 14 - Savings and Multi-employer Pension Plans (Details Textual) $ in Thousands, € in Millions, £ in Millions	Jan. 01, 2019	Jun. 30, 2018USD ($)	Jun. 30, 2018EUR (€)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2014USD ($)	Nov. 07, 2018GBP (£)	Dec. 31, 2015USD ($)
Other Defined Contribution Plan [Member]
Defined Contribution Plan, Cost				$ 700	$ 700	$ 700
United Kingdom Merchant Navy Officers Pension Fund [Member] | Foreign Pension Plan [Member]
Pension and Other Postretirement Benefits Cost (Reversal of Cost), Total							$ 19,400
Merchant Navy Ratings Pension Fund [Member]
Liability, Defined Benefit Pension Plan, Current				400
Multiemployer Plan, Contributions by Employer		$ 1,190	€ 0.9
Merchant Navy Ratings Pension Fund [Member] | Foreign Pension Plan [Member]
Pension and Other Post-retirement Benefit Plans, Total Funding Deficit								£ 9	$ 6,900
Liability, Defined Benefit Pension Plan, Current				1,500
Liability, Defined Benefit Pension Plan, Noncurrent				$ 1,900
Subsequent Event [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	1.00%

Note 15 - Share Based Compens_3

Note 15 - Share Based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Payments for Distribution of Restricted Stock, Spin-off		$ 2,700
Distribution of Restricted Stock in Connection with Spin-off		120,693
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total	$ 6,800	$ 5,200
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance	$ 14.81
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	8 years 359 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	805,566	613,700
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	9 years 8 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Restricted Stock [Member]
Distribution of Restricted Stock in Connection with Spin-off		120,693
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 12.63
Restricted Stock, Spin-off [Member]
Allocated Share-based Compensation Expense, Total		$ 600
2017 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	2,174,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	1,157,924
Allocated Share-based Compensation Expense, Total	$ 4,400	$ 800
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance	$ 9.99	$ 6.42
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	0.00%	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	50.40%	52.50%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Discount for Postvesting Restrictions	2.79%	2.22%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	6 years	6 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 800
2017 Equity Incentive Plan [Member] | Restricted Stock [Member]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 165 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 21.63	$ 12.50
2017 Equity Incentive Plan [Member] | Restricted Stock [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year
2017 Equity Incentive Plan [Member] | Restricted Stock [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
2017 Equity Incentive Plan [Member] | Employee Stock Option [Member]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 291 days
2017 Equity Incentive Plan [Member] | Employee Stock Option [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year
2017 Equity Incentive Plan [Member] | Employee Stock Option [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	300,000
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date		85.00%

Note 15 - Share Based Compens_4

Note 15 - Share Based Compensation - Equity Incentive Plan Transactions (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Distributed by SEACOR Holdings in connection with the Spin-off (in shares)		120,693
Outstanding as of the beginning of year (in shares)	613,700
Granted - 2017 Plan (in shares)	258,491	613,700
Exercised (in shares)	66,625
Forfeited (in shares)
Expired (in shares)
Outstanding as of the end of year (in shares)	805,566	613,700
Director Stock Awards [Member]
Granted (in shares)	19,285	3,000
Restricted Stock [Member]
Granted (in shares)	120,600	1,000
Outstanding as of the beginning of year (in shares)	121,693
Distributed by SEACOR Holdings in connection with the Spin-off (in shares)		120,693
Vested (in shares)	49,947
Forfeited (in shares)
Outstanding as of the end of year (in shares)	192,346	121,693

Note 15 - Share Based Compens_5

Note 15 - Share Based Compensation - Restricted Stock Transactions (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Outstanding as of the beginning of year (in shares)	121,693
Non-Vested, weight average grant price (in dollars per share)	$ 24.01
Granted (in shares)	120,600	1,000
Granted, weight average grant price (in dollars per share)	$ 12.63
Vested, shares (in shares)	49,947
Vested, weight average grant price (in dollars per share)	$ 24.85
Outstanding as of the end of year (in shares)	192,346	121,693
Non-Vested, weight average grant price (in dollars per share)	$ 22.32	$ 24.01

Note 15 - Share Based Compens_6

Note 15 - Share Based Compensation - Stock Option Transactions (Details) - $ / shares		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Non-Vested, shares (in shares)		613,700
Non-Vested, weight average grant price (in dollars per share)		$ 12.50
Granted, shares (in shares)		258,491	613,700
Granted, weight average grant price (in dollars per share)		$ 19.70
Exercise of options (in shares)		66,625
Exercised (in dollars per share)		$ 12.50
Non-Vested, shares (in shares)		805,566	613,700
Non-Vested, weight average grant price (in dollars per share)		$ 14.81	$ 12.50
Exercisable, shares (in shares)	[1]	261,691
Exercisable, weight average grant price (in dollars per share)		$ 14.02
[1]	The weighted average remaining contractual term is 8.9849 years.

Note 16 - Related Party Trans_3

Note 16 - Related Party Transactions (Details Textual)	Jan. 25, 2019USD ($)	Jan. 25, 2019GBP (£)	Nov. 30, 2015USD ($)	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Related Party Transaction, Rate				0.50%
Interest Expense, Related Party				$ 300,000	$ 300,000	$ 400,000
Related Party Transaction, Amounts of Transaction					$ 11,214,000	12,655,000
Windcat Workboats [Member]
Business Acquisition, Percentage of Voting Interests Acquired					12.50%
OSV Partners [Member]
Revenue from Related Parties				600,000	$ 600,000	500,000
Proceeds from Sale of Interest in Partnership Unit				$ 7,500,000
Equity Method Investment, Ownership Percentage				30.40%
OSV Partners [Member] | General Partner [Member]
Equity Method Investment, Ownership Percentage				38.60%
OSV Partners [Member] | Series A Preferred Stock [Member]
Proceeds from Issuance of Redeemable Preferred Stock				$ 2,500,000
Equity Method Investment, Ownership Percentage				43.00%
OSV Partners [Member] | Second Lien Debt [Member]
Proceeds from Issuance of Debt				$ 5,000,000
Equity Method Investment, Ownership Percentage				43.00%
Restricted Stock [Member]
Adjustments to Additional Paid in Capital, Other				$ 2,700,000
Stock Issued During Period, Shares, Restricted Stock Award, Gross | shares				120,693
Share Distribution [Member]
Related Party Transaction, Amounts of Transaction				$ 6,700,000
SEACOR Holdings [Member]
Related Party Transaction, Amounts of Transaction				9,400,000
Officer [Member] | OSV Partners [Member] | Limited Partner [Member] | Fabrikant [Member]
Limited Partners' Capital Account, Total				300,000
Officer [Member] | OSV Partners [Member] | Limited Partner [Member] | Gellert [Member]
Limited Partners' Capital Account, Total				$ 400,000
Officer [Member] | OSV Partners [Member] | Limited Partner [Member] | Fabrikant and Gellert [Member]
Equity Method Investment, Ownership Percentage				31.70%
Officer [Member] | OSV Partners [Member] | Series A Preferred Stock [Member] | General Partner [Member]
Equity Method Investment, Ownership Percentage				3.90%
General Partners' Capital Account, Total				$ 100,000
Officer [Member] | OSV Partners [Member] | Second Lien Debt [Member] | General Partner [Member]
Equity Method Investment, Ownership Percentage				3.90%
General Partners' Capital Account, Total				$ 200,000
Transition Services Agreement [Member]
Related Party Transaction, Amounts of Transaction				4,500,000	3,300,000
Management Services [Member]
Related Party Transaction, Amounts of Transaction					1,932,000	4,365,000
General and Administrative Expense [Member]
Related Party Transaction, Amounts of Transaction			$ 3,400,000
Maximum [Member] | Officer [Member] | OSV Partners [Member]
Limited Partners' Capital Account, Total				$ 1,500,000
Maximum [Member] | Officer [Member] | OSV Partners [Member] | Limited Partner [Member]
Equity Method Investment, Ownership Percentage				3.90%
Maximum [Member] | Officer [Member] | OSV Partners [Member] | General Partner [Member]
Equity Method Investment, Ownership Percentage				5.00%
General Partners' Capital Account, Total				$ 300,000
Maximum [Member] | Transition Services Agreement [Member]
Related Party Transaction, Amounts of Transaction				6,300,000
Maximum [Member] | Management Services [Member]
Related Party Transaction, Amounts of Transaction				7,700,000
Restructuring Charges [Member]
Related Party Transaction, Amounts of Transaction				6,000,000
Restructuring Charges [Member] | Maximum [Member]
Related Party Transaction, Amounts of Transaction				3,000,000
Employee Severance [Member]
Related Party Transaction, Amounts of Transaction				0	700,000
SEACOR Holdings [Member]
Revenue from Related Parties					100,000	$ 100,000
Guarantor Obligations, Maximum Exposure, Undiscounted				40,600,000	$ 69,100,000
Allocated Share-based Compensation Expense, Total				$ 1,700,000
Seabulk Overseas [Member] | Subsequent Event [Member] | Windcat Workboats [Member]
Ownership Percentage	100.00%	100.00%
Seabulk Overseas [Member] | Windcat Workboats [Member] | Subsequent Event [Member]
Business Acquisition, Percentage of Voting Interests Acquired	6.25%	6.25%
Business Combination, Consideration Transferred, Total	$ 2,000,000	£ 1,552,780

Note 16 - Related Party Trans_4

Note 16 - Related Party Transactions - Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related party transactions		$ 11,214	$ 12,655
Health Insurance [Member]
Related party transactions		899	3,702
Stock Compensation Plan [Member]
Related party transactions		8,383	4,588
Management Services [Member]
Related party transactions		$ 1,932	$ 4,365

Note 17 - Commitments and Con_3

Note 17 - Commitments and Contingencies (Details Textual) $ in Thousands	Dec. 31, 2018USD ($)
Unrecorded Unconditional Purchase Obligation, Total	$ 78,178
Unrecorded Unconditional Purchase Obligation, Due within Four Years	20,200
Windcat Workboats Ltd. [Member]
Line of Credit Facility, Remaining Borrowing Capacity	$ 2,500
Minimum [Member]
Lessee, Operating Lease, Term of Contract	1 year
Maximum [Member]
Lessee, Operating Lease, Term of Contract	3 years
FSV Offshore Support Vessels [Member]
Unrecorded Unconditional Purchase Obligation, Maximum Quantity	4
Supply Vessels [Member]
Unrecorded Unconditional Purchase Obligation, Maximum Quantity	3
Crew Transfer Vessels [Member]
Unrecorded Unconditional Purchase Obligation, Maximum Quantity	2
Platform Supply Vessels [Member]
Unrecorded Unconditional Purchase Obligation, Maximum Quantity	3

Note 17 - Commitments and Con_4

Note 17 - Commitments and Contingencies - Expected Payment (Details) $ in Thousands	Dec. 31, 2018USD ($)
2019	$ 51,132
2020	27,046
	$ 78,178

Note 18 - Major Customers and_3

Note 18 - Major Customers and Segment Information (Details Textual) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Revenue from Contract with Customer, Including Assessed Tax	$ 51,721	$ 60,701	$ 70,255	$ 70,932	$ 34,304	$ 42,323	$ 47,813	$ 49,343	$ 253,609	$ 173,783	$ 215,636
Assets, Total	1,102,935				1,008,504				1,102,935	1,008,504
Equity Method Investments	121,773				92,169				121,773	92,169
MexMar [Member]
Equity Method Investments	53,840				60,980				53,840	60,980
Other Equity Method Investment [Member]
Equity Method Investments	65,800								65,800
Corporate Segment [Member]
Assets, Total	$ 153,151				$ 169,346				$ 153,151	$ 169,346	$ 22,427
Customer Concentration Risk [Member] | Sales Revenue, Net [Member]
Number of Major Customers									10	10	10
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | Perenco [Member]
Revenue from Contract with Customer, Including Assessed Tax									$ 26,500	$ 26,800	$ 28,400
Concentration Risk, Percentage									10.30%	15.20%	13.20%
Customer Concentration Risk [Member] | Sales Revenue, Net [Member] | Ten Largest Customers [Member]
Concentration Risk, Percentage									47.00%	59.00%	58.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Non-US [Member]
Revenue from Contract with Customer, Including Assessed Tax									$ (1,300)	$ 1,900	$ (4,200)
Concentration Risk, Percentage									79.00%	87.00%	85.00%

Note 18 - Major Customers and_4

Note 18 - Major Customers and Segment Information - Summary of Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Operating Revenues	$ 51,721		$ 60,701	$ 70,255	$ 70,932	$ 34,304		$ 42,323	$ 47,813	$ 49,343	$ 253,609		$ 173,783		$ 215,636
Direct Costs and Expenses											175,091		146,651		149,348
Direct Vessel Profit											78,518		27,132		66,288
Administrative and general											52,813		56,217		49,308
Depreciation and amortization											72,246		62,779		58,069
											136,534		131,944		124,954
Losses on Asset Dispositions and Impairments, Net											(8,747)		(23,547)		(116,222)
Operating Loss	(24,414)		$ (21,002)	$ (10,158)	$ (11,189)	(18,585)		$ (44,815)	$ (29,129)	$ (35,830)	(66,763)		(128,359)		(174,888)
Historical cost	1,242,733	[1]				1,179,836	[1]				1,242,733	[1]	1,179,836	[1]	958,759
Accumulated depreciation	(561,272)					(560,160)					(561,272)		(560,160)		(540,619)
Net book value	681,461					619,676					681,461		619,676		418,140
Total Assets(1)	949,784	[2]				839,158	[3]				949,784	[2]	839,158	[3]	992,692	[4]
Leased-in Equipment [Member]
Operating expenses											11,475		12,948		17,577
Time Charter [Member]
Operating Revenues											222,252		160,545		186,327
Bareboat Charter [Member]
Operating Revenues											4,635		4,636		8,833
Other Direct Costs and Expenses [Member]
Operating Revenues											26,722		8,602		20,476
Direct Costs and Expenses											11,148		9,905		7,331
Personnel [Member]
Direct Costs and Expenses											95,028		81,500		95,144
Repairs and Maintenance [Member]
Direct Costs and Expenses											33,279		27,655		21,282
Drydocking [Member]
Direct Costs and Expenses											11,587		9,035		7,821
Insurance and Loss Reserves [Member]
Direct Costs and Expenses											7,074		6,524		5,682
Fuel, Lubes and Supplies [Member]
Direct Costs and Expenses											16,975		12,032		12,088
UNITED STATES
Operating Revenues											53,564		22,296		32,856
Direct Costs and Expenses											32,700		26,063		30,280
Direct Vessel Profit											20,864		(3,767)		2,576
Administrative and general
Depreciation and amortization											23,227		22,060		27,052
Historical cost	432,336					410,475					432,336		410,475		404,226
Accumulated depreciation	(224,737)					(230,636)					(224,737)		(230,636)		(233,075)
Net book value	207,599					179,839					207,599		179,839		171,151
Total Assets(1)	351,748	[2]				310,675	[3]				351,748	[2]	310,675	[3]	325,190	[4]
UNITED STATES | Leased-in Equipment [Member]
Operating expenses											7,420		8,152		7,975
UNITED STATES | Time Charter [Member]
Operating Revenues											38,802		18,079		28,902
UNITED STATES | Bareboat Charter [Member]
Operating Revenues
UNITED STATES | Other Direct Costs and Expenses [Member]
Operating Revenues											14,762		4,217		3,954
Direct Costs and Expenses											393		249		271
UNITED STATES | Personnel [Member]
Direct Costs and Expenses											18,708		15,621		22,305
UNITED STATES | Repairs and Maintenance [Member]
Direct Costs and Expenses											5,152		3,594		2,721
UNITED STATES | Drydocking [Member]
Direct Costs and Expenses											1,957		1,828		228
UNITED STATES | Insurance and Loss Reserves [Member]
Direct Costs and Expenses											2,922		3,286		3,363
UNITED STATES | Fuel, Lubes and Supplies [Member]
Direct Costs and Expenses											3,568		1,485		1,392
Africa [Member]
Operating Revenues											51,508		33,946		37,562
Direct Costs and Expenses											34,188		28,367		21,924
Direct Vessel Profit											17,320		5,579		15,638
Administrative and general
Depreciation and amortization											10,453		9,280		6,720
Historical cost	184,361					192,600					184,361		192,600		136,428
Accumulated depreciation	(55,206)					(57,228)					(55,206)		(57,228)		(60,794)
Net book value	129,155					135,372					129,155		135,372		75,634
Total Assets(1)	140,335	[2]				140,173	[3]				140,335	[2]	140,173	[3]	96,847	[4]
Africa [Member] | Leased-in Equipment [Member]
Operating expenses											3,843		3,870		3,898
Africa [Member] | Time Charter [Member]
Operating Revenues											43,847		32,866		36,706
Africa [Member] | Bareboat Charter [Member]
Operating Revenues
Africa [Member] | Other Direct Costs and Expenses [Member]
Operating Revenues											7,661		1,080		856
Direct Costs and Expenses											4,313		3,319		2,519
Africa [Member] | Personnel [Member]
Direct Costs and Expenses											16,538		13,419		12,628
Africa [Member] | Repairs and Maintenance [Member]
Direct Costs and Expenses											6,330		5,957		2,628
Africa [Member] | Drydocking [Member]
Direct Costs and Expenses											2,085		2,180		1,098
Africa [Member] | Insurance and Loss Reserves [Member]
Direct Costs and Expenses											1,096		677		539
Africa [Member] | Fuel, Lubes and Supplies [Member]
Direct Costs and Expenses											3,826		2,815		2,512
Middle East and Asia [Member]
Operating Revenues											49,185		33,884		53,887
Direct Costs and Expenses											38,718		37,299		35,117
Direct Vessel Profit											10,467		(3,415)		18,770
Administrative and general
Depreciation and amortization											18,762		17,724		11,550
Historical cost	306,897					326,378					306,897		326,378		197,389
Accumulated depreciation	(81,378)					(100,435)					(81,378)		(100,435)		(97,433)
Net book value	225,519					225,943					225,519		225,943		99,956
Total Assets(1)	260,002	[2]				234,471	[3]				260,002	[2]	234,471	[3]	140,166	[4]
Middle East and Asia [Member] | Leased-in Equipment [Member]
Operating expenses													862		4,389
Middle East and Asia [Member] | Time Charter [Member]
Operating Revenues											50,072		33,410		41,657
Middle East and Asia [Member] | Bareboat Charter [Member]
Operating Revenues
Middle East and Asia [Member] | Other Direct Costs and Expenses [Member]
Operating Revenues											(887)		474		12,230
Direct Costs and Expenses											3,980		5,240		3,247
Middle East and Asia [Member] | Personnel [Member]
Direct Costs and Expenses											16,806		16,883		18,381
Middle East and Asia [Member] | Repairs and Maintenance [Member]
Direct Costs and Expenses											11,172		9,037		6,426
Middle East and Asia [Member] | Drydocking [Member]
Direct Costs and Expenses											1,362		968		2,117
Middle East and Asia [Member] | Insurance and Loss Reserves [Member]
Direct Costs and Expenses											1,371		1,444		731
Middle East and Asia [Member] | Fuel, Lubes and Supplies [Member]
Direct Costs and Expenses											4,027		3,727		4,215
Brazil, Mexico, Central and South America [Member]
Operating Revenues											23,532		8,165		10,209
Direct Costs and Expenses											8,388		1,739		2,527
Direct Vessel Profit											15,144		6,426		7,682
Administrative and general
Depreciation and amortization											7,908		3,608		4,083
Historical cost	124,177					72,484					124,177		72,484		57,744
Accumulated depreciation	(57,002)					(37,281)					(57,002)		(37,281)		(34,455)
Net book value	67,175					35,203					67,175		35,203		23,289
Total Assets(1)	137,983	[2]				103,135	[3]				137,983	[2]	103,135	[3]	94,373	[4]
Brazil, Mexico, Central and South America [Member] | Leased-in Equipment [Member]
Operating expenses															913
Brazil, Mexico, Central and South America [Member] | Time Charter [Member]
Operating Revenues											17,343		2,977		196
Brazil, Mexico, Central and South America [Member] | Bareboat Charter [Member]
Operating Revenues											4,635		4,636		8,833
Brazil, Mexico, Central and South America [Member] | Other Direct Costs and Expenses [Member]
Operating Revenues											1,554		552		1,180
Direct Costs and Expenses											1,130		117		114
Brazil, Mexico, Central and South America [Member] | Personnel [Member]
Direct Costs and Expenses											4,399		809		2,117
Brazil, Mexico, Central and South America [Member] | Repairs and Maintenance [Member]
Direct Costs and Expenses											1,011		274		232
Brazil, Mexico, Central and South America [Member] | Drydocking [Member]
Direct Costs and Expenses											128
Brazil, Mexico, Central and South America [Member] | Insurance and Loss Reserves [Member]
Direct Costs and Expenses											495		316		43
Brazil, Mexico, Central and South America [Member] | Fuel, Lubes and Supplies [Member]
Direct Costs and Expenses											1,225		223		21
Europe [Member]
Operating Revenues											75,820		75,492		81,122
Direct Costs and Expenses											61,097		53,183		59,500
Direct Vessel Profit											14,723		22,309		21,622
Administrative and general
Depreciation and amortization											11,896		10,107		8,664
Historical cost	194,963					177,899					194,963		177,899		162,972
Accumulated depreciation	(142,949)					(134,580)					(142,949)		(134,580)		(114,862)
Net book value	52,014					43,319					52,014		43,319		48,110
Total Assets(1)	$ 59,716	[2]				$ 50,704	[3]				59,716	[2]	50,704	[3]	84,783	[4]
Europe [Member] | Leased-in Equipment [Member]
Operating expenses											212		64		402
Europe [Member] | Time Charter [Member]
Operating Revenues											72,188		73,213		78,866
Europe [Member] | Bareboat Charter [Member]
Operating Revenues
Europe [Member] | Other Direct Costs and Expenses [Member]
Operating Revenues											3,632		2,279		2,256
Direct Costs and Expenses											1,332		980		1,180
Europe [Member] | Personnel [Member]
Direct Costs and Expenses											38,577		34,768		39,713
Europe [Member] | Repairs and Maintenance [Member]
Direct Costs and Expenses											9,614		8,793		9,275
Europe [Member] | Drydocking [Member]
Direct Costs and Expenses											6,055		4,059		4,378
Europe [Member] | Insurance and Loss Reserves [Member]
Direct Costs and Expenses											1,190		801		1,006
Europe [Member] | Fuel, Lubes and Supplies [Member]
Direct Costs and Expenses											$ 4,329		$ 3,782		$ 3,948
[1]	Includes property and equipment acquired in business acquisitions at acquisition date fair value, and net of the impact of recognized impairment charges.
[2]	Total assets exclude $153,151 thousand of corporate assets.
[3]	Total assets exclude $169,346 thousand of corporate assets.
[4]	Total assets exclude $153,151 thousand of corporate assets.

Note 18 - Major Customers and_5

Note 18 - Major Customers and Segment Information - Income (Loss) in Equity Method Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income (Loss) from Equity Method Investments, Total	$ (3,415)	$ 4,077	$ (6,314)
MexMar [Member]
Income (Loss) from Equity Method Investments, Total	2,736	10,103	3,556
Other Offshore Marine Services Joint Ventures [Member]
Income (Loss) from Equity Method Investments, Total	$ (6,151)	$ (6,026)	$ (9,870)

Note 19 - Supplemental Inform_3

Note 19 - Supplemental Information for Statements of Cash Flows - Supplemental Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income taxes (paid) refunded, net	$ (316)	$ 33,773	$ 10,224
Interest paid, excluding capitalized interest	21,031	9,216	2,698
Exchange of receivable for investment in 50% or less owned company		1,000
Equipment received to settle notes receivable			$ 11,900

Note 20 - Subsequent Events (De

Note 20 - Subsequent Events (Details Textual)	Jan. 25, 2019USD ($)	Jan. 25, 2019GBP (£)	Jan. 09, 2019shares	Dec. 31, 2019	Dec. 31, 2018	[1]	Dec. 31, 2017	Dec. 31, 2016
Number of Equipment Acquired					8		11	17
Windcat Workboats [Member]
Business Acquisition, Percentage of Voting Interests Acquired							12.50%
Seabulk Overseas [Member] | Scenario, Forecast [Member] | Windcat Workboats [Member]
Ownership Percentage				100.00%
Seabulk Overseas [Member] | Windcat Workboats [Member] | Scenario, Forecast [Member]
Business Acquisition, Percentage of Voting Interests Acquired				6.25%
Number of Acquisition Transactions				2
Fast Support Vessels [Member]
Number of Equipment Acquired							6	12
Subsequent Event [Member] | Seabulk Overseas [Member] | Windcat Workboats [Member]
Ownership Percentage	100.00%	100.00%
Subsequent Event [Member] | Seabulk Overseas [Member] | Windcat Workboats [Member]
Business Acquisition, Percentage of Voting Interests Acquired	6.25%	6.25%
Business Combination, Consideration Transferred, Total	$ 2,000,000	£ 1,552,780
Subsequent Event [Member] | Fast Support Vessels [Member] | Domestic U.S. Holders Affiliated With The McCall Family of Louisiana [Member]
Number of Equipment Acquired			3
Subsequent Event [Member] | Fast Support Vessels [Member] | Domestic U.S. Holders Affiliated With The McCall Family of Louisiana [Member] | Revenue Sharing Pooling Agreement [Member]
Acquired Vessels Prior Operation Period			10 years
Number of Vessels			4
Subsequent Event [Member] | Fast Support Vessels [Member] | Domestic U.S. Holders Affiliated With The McCall Family of Louisiana [Member] | Private Placement [Member]
Stock Issued During Period, Shares, Purchase of Assets			603,872
[1]	Excludes two AHTS vessels purchased from Managed Entity Seacor 88 and Seacor 888, and one crew transfer vessel purchased from the Company's joint venture FRS Windcat Offshore Logistics.

Note 21 - Quarterly Financial_3

Note 21 - Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue from Contract with Customer, Including Assessed Tax	$ 51,721	$ 60,701	$ 70,255	$ 70,932	$ 34,304	$ 42,323	$ 47,813	$ 49,343	$ 253,609	$ 173,783	$ 215,636
Operating Loss	(24,414)	(21,002)	(10,158)	(11,189)	(18,585)	(44,815)	(29,129)	(35,830)	(66,763)	(128,359)	(174,888)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	(31,688)	(26,629)	(15,766)	(7,969)	(7,599)	(36,489)	(22,356)	27,904	(82,052)	(38,540)	(133,150)
Net Income (Loss) attributable to SEACOR Marine Holdings Inc.	$ (28,833)	$ (25,024)	$ (15,957)	$ (7,794)	$ (7,395)	$ (33,992)	$ (20,475)	$ 28,961	$ (77,608)	$ (32,901)	$ (132,047)
Basic Income (Loss) Per Common Share of SEACOR Marine Holdings Inc. (in dollars per share)	$ (1.64)	$ (1.19)	$ (0.71)	$ (0.35)	$ (0.42)	$ (1.93)	$ (1.17)	$ 1.65
Diluted Income (Loss) Per Common Share of SEACOR Marine Holdings Inc. (in dollars per share)	$ (1.64)	$ (1.19)	$ (0.71)	$ (0.35)	$ (0.42)	$ (1.93)	$ (1.25)	$ 1.20

Schedule II - Valuation and Q_3

Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts (deducted from trade and notes receivable)		$ 4,039	$ 5,359	$ 1,177
Allowance for doubtful accounts (deducted from trade and notes receivable)		(928)	(1,283)
Allowance for doubtful accounts (deducted from trade and notes receivable)	[1]	(2,251)	(37)	(98)
Allowance for doubtful accounts (deducted from trade and notes receivable)		$ 860	$ 4,039	5,359
Allowance for doubtful accounts (deducted from trade and notes receivable)				$ 4,280
[1]	Trade receivable amounts deemed uncollectible that were removed from accounts receivable and allowance for doubtful accounts.