SEACOR Marine (SMHI) 10-K 4 Mar 20 2019 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 28, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	SMHI
Entity Registrant Name	SEACOR Marine Holdings Inc.
Entity Central Index Key	0001690334
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Title of 12(b) Security	Common stock
Security Exchange Name	NYSE
Entity File Number	1-37966
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-2564547
Entity Address, Address Line One	12121 Wickchester Lane
Entity Address, Address Line Two	Suite 500
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77079
City Area Code	346
Local Phone Number	980-1700
Document Annual Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		21,881,489
Entity Public Float			$ 325.6
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Documents Incorporated by Reference	Portions of the Registrant’s definitive proxy statement for its 2020 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission (the "SEC") pursuant to Regulation 14A within 120 days after the end of the Registrant’s last fiscal year is incorporated by reference into Part III of this Annual Report on Form 10-K.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Current Assets:
Cash and cash equivalents		$ 83,943	$ 91,597
Restricted cash		3,104	1,657
Receivables:
Trade, net of allowance for doubtful accounts of $455 and $860 in 2019 and 2018, respectively		49,128	55,048
Other		18,531	11,292
Inventories		1,228	1,977
Prepaid expenses and other		2,612	2,239
Assets held for sale			15,222
Total current assets		158,546	179,032
Property and Equipment:
Historical cost	[1]	976,978	1,116,583
Accumulated depreciation		(358,962)	(461,399)
Property and equipment		618,016	655,184
Construction in progress		74,344	88,918
Net property and equipment		692,360	744,102
Right-of-Use Asset - Operating Leases		17,313
Investments, at Equity, and Advances to 50% or Less Owned Companies		124,680	121,773
Construction Reserve Funds		12,893	28,061
Other Assets		3,401	3,690
Assets Held for Sale			26,280
Total assets		1,009,193	1,102,938
Current Liabilities:
Current portion of operating lease liabilities		15,099
Current portion of long-term debt		17,802	16,812
Accounts payable and accrued expenses		25,691	18,089
Due to SEACOR Holdings		74	452
Accrued wages and benefits		1,832	4,122
Accrued interest		731	1,101
Accrued income taxes			1,918
Accrued capital, repair and maintenance expenditures		15,997	18,757
Deferred and Unearned revenues		5,327	1,460
Accrued insurance deductibles and premiums		3,564	3,403
Accrued professional fees		871	918
Derivatives		3,009	1,659
Other current liabilities		4,820	12,400
Liabilities associated with assets held for sale			2,526
Total current liabilities		94,817	83,617
Long-Term Operating Lease Liabilities		9,822
Long-Term Debt		380,251	387,854
Conversion Option Liability on Convertible Senior Notes		5,205	5,276
Deferred Income Taxes		33,905	44,685
Deferred Gains and Other Liabilities		6,269	26,571
Total liabilities		530,269	548,003
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; 21,928,674 and 20,443,215 shares issued in 2019 and 2018, respectively		219	204
Additional paid-in capital		429,318	415,372
Retained earnings		27,076	126,834
Shares held in treasury of 47,185 and 4,007 in 2019 and 2018, respectively, at cost		(669)	(91)
Accumulated other comprehensive loss, net of tax		1,548	(16,788)
Total stockholders equity		457,492	525,531
Noncontrolling interests in subsidiaries		21,432	29,404
Total equity		478,924	554,935
Total liabilities and equity		$ 1,009,193	$ 1,102,938
[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 (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Trade receivables, allowance for doubtful accounts	$ 455	$ 860
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)	21,928,674	20,443,215
Shares held in treasury (in shares)	47,185	4,007

Consolidated Statements of Loss

Consolidated Statements of Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Operating Revenues	$ 201,492	$ 203,567	$ 123,421
Costs and Expenses:
Operating	123,725	132,274	104,821
Administrative and general	44,726	46,454	49,865
Lease expense	16,158	13,239	14,449
Depreciation and amortization	64,012	68,841	60,307
Costs and expenses	248,621	260,808	229,442
Losses on Asset Dispositions and Impairments, Net	(5,397)	(11,268)	(23,623)
Operating Loss	(52,526)	(68,509)	(129,644)
Other Income (Expense):
Interest income	1,445	1,222	1,797
Interest expense	(30,056)	(27,404)	(16,044)
SEACOR Holdings management fees			(3,208)
SEACOR Holdings guarantee fees	(108)	(29)	(201)
Loss on Debt Extinguishment		(638)
Marketable security gains (losses), net			10,931
Derivative gains, net	71	2,854	20,256
Foreign currency losses, net	(1,661)	(1,397)	(1,671)
Other, net	(1)	677	(6)
Nonoperating income expense	(30,310)	(24,715)	11,854
Loss from Continuing Operations Before Tax Benefit and Equity in Earnings (Losses) of 50% or Less Owned Companies	(82,836)	(93,224)	(117,790)
Income Tax Expense (Benefit):
Current	4,955	9,383	(13,404)
Deferred	(12,867)	(22,737)	(61,006)
Income Tax Expense (Benefit)	(7,912)	(13,354)	(74,410)
Loss Before Equity in (Losses) Earnings of 50% or Less Owned Companies	(74,924)	(79,870)	(43,380)
Equity in (Losses) Earnings of 50% or Less Owned Companies, Net of Tax	(14,304)	(3,552)	3,851
Loss from Continuing Operations	(89,228)	(83,422)	(39,529)
(Loss) Income on Discontinued Operations, Net of Tax (including loss on disposal of $9,106)	(9,467)	1,370	989
Net Loss	(98,695)	(82,052)	(38,540)
Net Loss attributable to Noncontrolling Interests in Subsidiaries	(5,858)	(4,444)	(5,639)
Net Loss attributable to SEACOR Marine Holdings Inc.	$ (92,837)	$ (77,608)	$ (32,901)
Basic and Diluted Income (Loss) Per Common Share and Warrants of SEACOR Marine Holdings Inc.
Continuing operations	$ (3.55)	$ (3.77)	$ (1.93)
Discontinued operations	(0.40)	0.07	0.06
Basic and Diluted Income (Loss) Per Common Share and Warrants	$ (3.95)	$ (3.70)	$ (1.87)
Weighted Average Common Shares and Warrants Outstanding:
Basic and diluted shares	23,513,925	20,926,307	17,601,244

Consolidated Statements of Lo_2

Consolidated Statements of Loss (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Income Statement [Abstract]
Loss on disposal of business	$ 9,106

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Loss	$ (98,695)	$ (82,052)	$ (38,540)
Other Comprehensive Loss:
Foreign currency translation (losses) gains, net	20,157	(2,365)	4,654
Reclassification of foreign currency translation losses to foreign currency losses, net			0
Derivative (losses) gains on cash flow hedges	(1,901)	(1,939)	214
Other comprehensive income	18,163	(4,349)	5,375
Income tax (expense) benefit	173	(46)	(6,256)
Other comprehensive income, net	18,336	(4,395)	(881)
Comprehensive Loss	(80,359)	(86,447)	(39,421)
Comprehensive Loss attributable to Noncontrolling Interests in Subsidiaries	(5,858)	(4,544)	(5,364)
Comprehensive Loss attributable to SEACOR Marine Holdings Inc.	(74,501)	(81,903)	(34,057)
Interest Expense
Other Comprehensive Loss:
Reclassification of derivative gains (losses) on cash flow hedges	552	31	118
Equity Method Investments
Other Comprehensive Loss:
Reclassification of derivative gains (losses) on cash flow hedges	$ (645)	$ (76)	$ 389

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Loss (Parenthetical)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Reclassification of derivative losses on cash flow hedges to equity in earnings	50.00%	50.00%	50.00%

Consolidated Statements of Chan

Consolidated Statements of Changes In Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Non-Controlling Interests In Subsidiaries [Member]
Balance at Dec. 31, 2016						$ (11,337)
Net Loss	$ (38,540)
Other comprehensive loss	(881)
Balance at Dec. 31, 2017	523,166	$ 177	$ 303,996		$ 216,511	(12,493)	$ 14,975
Balance (in shares) at Dec. 31, 2017		17,675,356
Impact of adoption of accounting principle at Dec. 31, 2017	(12,069)				(12,069)
Balance at Dec. 31, 2017	511,097	$ 177	303,996		204,442	(12,493)	14,975
Issuance of Common Stock	42,996	$ 23	42,973
Issuance of Common Stock (in shares)		2,291,084
Issuance of Warrants	62,809		62,809
Amortization of employee share awards	3,494		3,494
Exercise of options	$ 833	$ 1	832
Exercise of options (in shares)	66,625	66,625
Exercise of Warrants		$ 3		$ (3)
Exercise of Warrants (in shares)		289,442		108
Restricted stock vesting	$ (88)			$ (88)
Restricted stock vesting (in shares)		116,701		3,899
Director share awards	893		893
Acquisition of consolidated joint venture	(12,037)						(12,037)
Issuance of noncontrolling interests	31,385		375				31,010
Net Loss	(82,052)				(77,608)		(4,444)
Other comprehensive loss	(4,395)					(4,295)	(100)
Balance at Dec. 31, 2018	$ 554,935	$ 204	415,372	$ (91)	126,834	(16,788)	29,404
Balance (in shares) at Dec. 31, 2018	20,443,215	20,439,208		4,007
Impact of adoption of accounting principle at Dec. 31, 2018	$ 10,416				10,416
Balance at Dec. 31, 2018	565,351	$ 204	415,372	$ (91)	137,250	(16,788)	29,404
Issuance of Common Stock	6,596	$ 7	6,589
Issuance of Common Stock (in shares)		653,872
Restricted stock grants	2	$ 2
Restricted stock grants (in shares)		245,400
Cancellation of restricted stock grants (in shares)		(2,200)
Amortization of employee share awards	5,046		5,046
Exercise of options	$ 1,421	$ 1	1,420
Exercise of options (in shares)	113,750	113,750
Exercise of Warrants	$ 3	$ 4		(1)
Exercise of Warrants (in shares)		444,391
Restricted stock vesting	(579)		(2)	$ (577)
Restricted stock vesting (in shares)		(43,129)		43,129
Director share awards	894	$ 1	893
Director share awards (in shares)		30,197		49
Acquisition of consolidated joint venture	(2,114)						(2,114)
Sale of Standby Safety Fleet	(17,399)				(17,399)
Dissolution of Entity	62				62
Net Loss	(98,695)				(92,837)		(5,858)
Other comprehensive loss	18,336					18,336
Balance at Dec. 31, 2019	$ 478,924	$ 219	$ 429,318	$ (669)	$ 27,076	$ 1,548	$ 21,432
Balance (in shares) at Dec. 31, 2019	21,928,674	21,881,489		47,185

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Continuing Operating Activities:
Net Loss	$ (98,334)	$ (83,422)	$ (39,529)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	64,012	68,841	60,307
Deferred financing cost amortization	1,182	2,018	2,344
Amortization of deferred gains against charter expense		(8,037)	(8,118)
Debt discount and issue cost amortization, net	5,662	5,348	4,448
Director share awards	894	893	681
Restricted stock amortization	5,046	3,494	638
Restricted stock vesting	(577)	(88)	88
Bad debt (recoveries) expense	(404)	(880)	(1,283)
Losses on asset dispositions and impairments, net	5,397	11,268	23,623
Loss on sale of Emergency Response Rescue Vessels ("ERRV")	9,106
Gain from other sales		(428)
Marketable security (gains) losses, net			(10,931)
Proceeds from sale of marketable securities			51,877
Derivative gains, net	(71)	(2,854)	(20,256)
Cash settlements on derivative transactions, net	(536)	1,372	(512)
Foreign currency losses, net	1,661	1,397	1,671
Deferred	(12,867)	(22,737)	(61,006)
Equity in (earnings) losses of 50% or less owned companies, net of tax	14,304	3,552	(3,851)
Dividends received from 50% or less owned companies	2,073	1,724	2,642
Changes in operating assets and liabilities:
Decrease (increase) in receivables	8,487	(18,621)	31,263
Decrease in prepaid expenses and other assets	103	1,054	6,243
Decrease (Increase) in accounts payable, accrued expenses and other liabilities	4,309	(23,239)	(2,703)
Net cash provided by (used in) operating activities	9,447	(59,345)	37,636
Cash Flows from Investing Activities:
Purchases of property and equipment	(55,456)	(51,578)	(68,983)
Cash settlements on derivative transactions, net			(369)
Proceeds from disposition of property and equipment	56,183	20,140	10,701
Cash impact of sale of ERRV fleet	(5,140)
Sale of subsidiary to joint venture		8,017
Investments in and advances to 50% or less owned companies	(17,417)	(43,725)	(5,469)
Return of investments and advances from 50% or less owned companies	461	16,263	7,553
Net decrease in construction reserve funds	15,168	17,300	32,848
Principal payments on notes due from equity investees	22	116
Cash assumed on consolidation of 50% or less owned companies			1,943
Business acquisitions, net of cash acquired			(9,751)
Net cash provided by (used in) investing activities	21,211	(33,467)	(31,527)
Cash Flows from Financing Activities:
Payments on long-term debt	(23,974)	(49,405)	(11,926)
Proceeds from issuance of long-term debt, net of issue costs		62,017	6,545
Proceeds from exercise of stock options and warrants	1,424	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	(3,392)		(3,693)
Net cash provided by (used in) financing activities	(25,942)	69,250	(11,730)
Effects of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	(17,642)	(699)	(1,236)
Net (Decrease) in Cash, Cash Equivalents and Restricted Cash, Continuing Operations	(12,926)	(24,261)	(6,857)
Cash Flows from Discontinued Operations:
Operating Activities	5,992	6,320	(2,897)
Investing Activities	(5,569)	2,318	104
Effects of Exchange Rate Changes on Cash, Restricted Cash and Cash Equivalents	2,698	(75)	3,430
Net Decrease in Cash, Restricted Cash and Cash Equivalents on Discontinued Operations	3,121	8,563	637
Net Decrease in Cash, Cash Equivalents and Restricted Cash	(9,805)	(15,699)	(6,220)
Cash, Cash Equivalents and Restricted Cash, Beginning of Year	96,852	112,551	118,771
Cash, Cash Equivalents and Restricted Cash, End of Year	87,047	$ 96,852	$ 112,551
ERRV Fleet Business
Cash Flows from Investing Activities:
Proceeds from disposition of property and equipment	$ 27,390

Nature of Operations and Accoun

Nature of Operations and Accounting Policies	12 Months Ended
	Dec. 31, 2019
Nature Of Operation And Accounting Policies [Abstract]
Nature of Operations and Accounting Policies	1. NATURE OF OPERATIONS AND ACCOUNTING POLICIES Nature of Operations and Segmentation. The consolidated financial statements include the accounts of SEACOR Marine and its consolidated subsidiaries (collectively referred to as the “Company”). The Company provides global marine and support transportation services to offshore oil, natural gas and windfarm facilities worldwide. The Company and its joint ventures operate a diverse fleet of offshore support and specialty vessels that (i) deliver cargo and personnel to offshore installations, (ii) handle anchors and mooring equipment required to tether rigs to the seabed, (iii) tow rigs and assist in placing them on location and moving them between regions, (iv) provide construction, well work-over and decommissioning support and (v) carry and launch equipment used underwater in drilling and well installation, maintenance, inspection and repair. Additionally, the Company’s vessels provide accommodations for technicians and specialists, safety support and emergency response services. The Company’s fleet also features crew transfer vessels (“CTVs”) used primarily in windfarm operations. 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. On December 2, 2019, the Company completed the sale of its North Sea standby safety business. Unless the context indicates otherwise, the footnotes to these financial statements reflect continuing operations after the disposition. The Company has identified the following five principal geographic regions as its reporting segments: United States, primarily Gulf of Mexico. The Company’s vessels in this market support deepwater anchor handling, fast cargo transport, general cargo transport, well intervention, work-over, decommissioning, and diving support operations. Africa, primarily West Africa. The Company’s vessels in this area generally support projects for major oil companies, primarily in Angola and Nigeria. Middle East and Asia. The Company’s vessels in this area generally support exploration, personnel transport and seasonal construction activities in Egypt, Israel, Malaysia and countries along the Arabian Gulf and Arabian Sea, such as Saudi Arabia, the United Arab Emirates and Qatar. Latin America. As of December 31, 2019, 34 vessels were located in this region, including four owned and 30 joint-ventured. Of these joint-ventured vessels, (i) 16 are owned by Mantenimiento Express Maritimo, S.A.P.I. de C.V. (“MexMar”), a joint venture company that is 49% owned by SEACOR Marine International LLC (“SMI”), a wholly owned subsidiary of SEACOR Marine, and 51% owned by subsidiaries of Proyectos Globales de Energía y Servicios CME, S.A. de C.V. (“CME”), (ii) 13 of such vessels are owned by MEXMAR Offshore International LLC (“MEXMAR Offshore”), a joint venture company that is 49% owned by SMI and 51% owned by a subsidiary of CME and (iii) one is owned by SEACOSCO. These vessels, consisting of a fleet of FSVs, supply, specialty and liftboat vessels, provide support for exploration and production activities in Mexico, Brazil and Guyana. From time to time, the Company’s vessels also work in Trinidad and Tobago, and Colombia. Europe, primarily North Sea. As of December 31, 2019, 43 vessels were located in this region supporting the construction and maintenance of offshore wind turbines, including 37 owned and six joint ventured. On December 2, 2019, the Company completed the sale of its North Sea standby safety business, comprised of 18 emergency response and rescue vessels (“ERRVs”) related vessels located in the North Sea providing standby safety and supply services The Spin-off. SEACOR Marine was previously a subsidiary of SEACOR Holdings Inc. (along with its consolidated subsidiaries, other than SEACOR Marine, collectively referred to as “SEACOR Holdings”). On June 1, 2017, SEACOR Holdings completed a spin-off of SEACOR Marine by way of a pro rata dividend of SEACOR Marine’s Common Stock, all of which was then held by SEACOR Holdings, to SEACOR Holdings’ shareholders of record as of May 22, 2017 (the “Spin-off”). SEACOR Marine entered into certain agreements with SEACOR Holdings to govern SEACOR Marine’s relationship with SEACOR Holdings following the Spin-off, including a Distribution Agreement, two Transition Services Agreements, an Employee Matters Agreement and a Tax Matters Agreement. Immediately following the Spin-off, SEACOR Marine began to operate as an independent, publicly traded company. Basis of Consolidation. The consolidated financial statements include the accounts of SEACOR Marine and its controlled subsidiaries. Control is generally deemed to exist if the Company has greater than 50% of the voting rights of a subsidiary. All significant intercompany accounts and transactions are eliminated in the combination and consolidation. 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% or less owned companies that it does not control but has the ability to exercise significant influence over the operating and financial policies of the business venture. Significant influence is generally deemed to exist if the Company has between 20% and 50% of the voting rights of a business venture, but may exist when the Company’s ownership percentage is less than 20%. In certain circumstances, the Company may have an economic interest in excess of 50% but may not control and consolidate the business venture. Conversely, the Company may have an economic interest less than 50% but may control and consolidate the business venture. The Company reports its investments in and advances to these business ventures in the accompanying consolidated balance sheets as investments, at equity, and advances to 50% or less owned companies. The Company reports its share of earnings from investments in 50% or less owned companies in the accompanying consolidated statements of loss as equity in earnings (losses) of 50% or less owned companies, net of tax. The Company employs the cost method of accounting for investments in 50% or less owned companies it does not control or exercise significant influence. These investments in private companies are carried at cost and are adjusted only for capital distributions and other-than-temporary declines in fair value. Certain reclassifications were made to previously reported amounts in the consolidated financial statements and notes thereto to make them consistent with the current period presentation. Use of Estimates. The preparation of financial statements in conformity with accounting principles generally accepted in the U.S. requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Such estimates include those related to deferred revenues, allowance for doubtful accounts, useful lives of property and equipment, impairments, income tax provisions and certain accrued liabilities. Actual results could differ from estimates and those differences may be material. 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 to three years and are typically billed on a monthly basis. The Company transfers control of the service to the customer and satisfies its performance obligation over the term of the contract, and therefore recognized revenue over the term of the contract while related costs are expensed as incurred. Revenue that does not meet these criteria is deferred until the criteria is met and such revenue is considered a contract liability. Contract liabilities, which are included in other current liabilities in the accompanying consolidated balance sheets, for the years ended December 31 were as follows (in thousands): 2019 2018 2017 Balance at beginning of year $ 1,327 $ 10,104 $ 6,953 Revenues deferred during the year 8,164 3,600 4,699 Revenues recognized during the year (4,705 ) (12,377 ) (1,548 ) Balance at end of year $ 4,786 $ 1,327 $ 10,104 As of December 31, 2019, the Company deferred revenues of $4.8 million primarily related to $2.0 million of prepaid vessel management fees, and $1.8 million related to the time charter of offshore support vessels to customers from which collections were not reasonably assured. 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 also participate in pooling arrangements. In a pooling arrangement, the time charter revenues of certain of the Company’s vessels are shared with the time charter revenues of certain vessels of similar type owned by non-affiliated vessel owners based upon an agreed formula. On January 9, 2019, the only active pooling arrangement was terminated, and three FSV’s were purchased by the Company. Contract or charter durations may range from several days to several years. Charters vary in length from short-term to multi-year periods, many with cancellation clauses and without early termination penalties. As a result of options and frequent renewals, the stated duration of charters may have little correlation with the length of time the vessel is contracted to provide services to a particular customer. Cash Equivalents. The Company considers all highly liquid investments with an original maturity of three months or less, when purchased, to be cash equivalents. Cash equivalents consist of U.S. treasury securities, money market instruments, time deposits and overnight investments. Restricted Cash. Restricted cash primarily relates to banking facility requirements. For the year ended December 31, cash, cash equivalents and restricted cash consists of: 2019 2018 Cash $ 83,943 $ 91,597 Cash equivalents — — Restricted cash 3,104 1,657 Total $ 87,047 $ 93,254 Marketable Securities. Marketable equity securities with readily determinable fair values and debt securities are reported in the accompanying consolidated balance sheets as marketable securities. These investments are stated at fair value, as determined by their market observable prices, with both realized and unrealized gains and losses reported in the accompanying consolidated statements of loss as marketable security losses, net. Short sales of marketable securities are stated at fair value in the accompanying consolidated balance sheets with both realized and unrealized losses reported in the accompanying consolidated statements of loss as marketable security gains (losses), net. Marketable securities are classified as trading securities for financial reporting purposes with gains and losses reported as operating activities in the accompanying consolidated statements of cash flows. Trade and Other Receivables. Customers are primarily major integrated national and international oil companies, large independent oil and natural gas exploration and production companies, and offshore windfarm operations. Customers are granted credit on a short-term basis and the related credit risks are minimal. Other receivables consist primarily of operating expenses the Company incurs in relation to vessels it manages for other entities, as well as insurance and income tax receivables. The Company routinely reviews its receivables and makes provisions for probable doubtful accounts; however, those provisions are estimates and actual results may materially differ from those estimates. Trade receivables are deemed uncollectible and are removed from accounts receivable and the allowance for doubtful accounts when collection efforts have been exhausted. Derivative Instruments. The Company accounts for derivatives through the use of a fair value concept whereby all of the Company’s derivative positions are stated at fair value in the accompanying consolidated balance sheets. Realized and unrealized gains and losses on derivatives not designated as hedges are reported in the accompanying consolidated statements of loss as Derivative gains (losses), net. Realized and unrealized gains and losses on derivatives designated as fair value hedges are recognized as corresponding increases or decreases in the fair value of the underlying hedged item to the extent they are effective, with any ineffective portion reported in the accompanying consolidated statements of loss as Derivative gains (losses), net. Realized and unrealized gains and losses on derivatives designated as cash flow hedges are reported as a component of other comprehensive loss in the accompanying consolidated statements of comprehensive loss to the extent they are effective and reclassified into earnings on the same line item associated with the hedged transaction and in the same period the hedged transaction affects earnings. Any ineffective portions of cash flow hedges are reported in the accompanying consolidated statements of loss as Derivative gains (losses), net. Realized and unrealized gains and losses on derivatives designated as cash flow hedges that are entered into by the Company’s 50% or less owned companies are also reported as a component of the Company’s other comprehensive loss in proportion to the Company’s ownership percentage, with reclassifications and ineffective portions being included in Equity in earnings (losses) of 50% or less owned companies, net of tax, in the accompanying consolidated statements of loss. Concentrations of Credit Risk. The Company is exposed to concentrations of credit risk associated with its cash and cash equivalents, restricted cash, construction reserve funds and derivative instruments. The Company minimizes its credit risk relating to these positions by monitoring the financial condition of the financial institutions and counterparties involved and by primarily conducting business with large, well-established financial institutions and diversifying its counterparties. The Company does not currently anticipate nonperformance by any of its significant counterparties. The Company is also exposed to concentrations of credit risk relating to its receivables due from customers described above. The Company does not generally require collateral or other security to support its outstanding receivables. The Company minimizes its credit risk relating to receivables by performing ongoing credit evaluations and, to date, credit losses have not been material. Inventories. Inventories, which consist of fuel and supplies, are stated at the lower of cost (using the first-in, first-out method) or market. The Company records write-downs, as needed, to adjust the carrying amount of inventories to the lower of cost or market. In the year ended December 31, 2019, 2018 and 2017, there were no inventory reserves. Property and Equipment. Equipment, stated at cost, is depreciated using the straight-line method over the estimated useful life of the asset to an estimated salvage value. With respect to offshore support vessels, the estimated useful life is typically based upon a newly built vessel being placed into service and represents the point at which it is typically not justifiable for the Company to continue to operate the vessel in the same or similar manner. From time to time, the Company may acquire older vessels that have already exceeded the Company’s useful life policy, in which case the Company depreciates such vessels based on its best estimate of remaining useful life, typically the next regulatory survey or certification date. As of December 31, 2019, the estimated useful life (in years) of each of the Company’s major categories of new offshore support vessels was as follows: 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 was as follows (in thousands): Historical Cost (1) Accumulated Depreciation Net Book Value 2019 Offshore support vessels: AHTS (2) $ 94,078 $ (73,095 ) $ 20,983 FSV (3) 388,460 (101,295 ) 287,165 Supply 44,958 (8,471 ) 36,487 Specialty 14,805 (10,466 ) 4,339 Liftboats 327,028 (93,166 ) 233,862 Crew transfer 82,645 (54,358 ) 28,287 General machinery and spares 7,650 (7,648 ) 2 Other (4) 17,354 (10,463 ) 6,891 $ 976,978 $ (358,962 ) $ 618,016 2018 Offshore support vessels: AHTS (2) $ 197,344 $ (168,731 ) $ 28,613 FSV (3) 404,310 (98,580 ) 305,730 Supply 64,284 (37,202 ) 27,082 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 (4) 13,443 (9,562 ) 3,881 $ 1,116,583 $ (461,399 ) $ 655,184 (1) Includes property and equipment acquired in business acquisitions at acquisition date fair value, and net of the impact of recognized impairment charges. (2) Anchor Handling Towing (“AHTS”) (3) Fast support vessels (“FSVs”). ( 4 ) Includes land, buildings, leasehold improvements, vehicles and other property and equipment. Depreciation and amortization expense from continuing operations totaled $64.0 million, $68.8 million and $60.3 million in 2019, 2018 and 2017, respectively. On December 2, 2019, the Company completed the sale of its North Sea standby business, comprised of 18 ERRVs with a net book value of $24.3 million. Depreciation and amortization expense totaled $3.5 million, $3.4 million and $2.5 million in 2019, 2018 and 2017, respectively. 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 $1.5 million, $2.4 million and $3.6 million in 2019, 2018 and 2017, respectively. Impairment of Long-Lived Assets. The Company performs an impairment analysis of long-lived assets used in operations, including intangible assets, when indicators of impairment are present. These indicators may include a significant decrease in the market price of a long-lived asset or asset group, a significant adverse change in the extent or manner in which a long-lived asset or asset group is being used or in its physical condition, or a current period operating or cash flow loss combined with a history of operating or cash flow losses or a forecast that demonstrates continuing losses associated with the use of a long-lived asset or asset group. If the carrying values of the assets are not recoverable, as determined by their estimated future undiscounted cash flows, the estimated fair value of the assets or asset groups are compared to their current carrying values and impairment charges are recorded if the carrying value exceeds fair value. As a result of the difficult conditions experienced in the offshore oil and natural gas markets beginning in the second half of 2014 and the corresponding reductions in utilization and rates per day worked of its fleet, the Company identified indicators of impairment and recognized impairment charges primarily associated with its AHTS fleet, its liftboat fleet, certain specialty vessels, vessels removed from service and goodwill. When reviewing its fleet for impairment, the Company groups vessels with similar operating and marketing characteristics, including cold-stacked vessels expected to return to active service, into vessel classes. All other vessels, including vessels retired and removed from service, are evaluated for impairment on a vessel by vessel basis. During the year ended December 31, 2019, the Company recorded non-cash impairment charges of $12.0 million primarily related to four anchor-handling towing supply (“AHTS”) vessels previously removed from service and adjusted to scrap value, and four fast support vessels (“FSV”) each of which has been adjusted to indicative sales price, and two leased-in vessels (one AHTS and one platform supply vessel “PSV”), adjusted for indicative future cash flows . During the year ended December 31, 2018, the Company recorded non-cash impairment charges of $14.6 million primarily associated with its AHTS fleet (four owned vessels and three leased-in vessels) and one specialty vessel. During the year ended December 31, 2017, the Company recorded non-cash impairment charges of $27.5 million primarily associated with its AHTS vessels, one leased-in supply vessel removed from service as it is not expected to be marketed prior to the expiration of its lease, one owned FSV removed from service and two owned in-service specialty vessels. Estimated fair values for the Company’s owned vessels were established by independent appraisers and other market data such as recent sales of similar vessels (see Note 11). If market conditions further decline from the depressed utilization and rates per day worked experience over the last three years, fair values based on future appraisals could decline significantly. The Company’s other vessel classes and other individual vessels in active service and cold-stacked status, for which no impairment was deemed necessary, have generally experienced a less severe decline in utilization and rates per day worked based on specific market factors. The market factors include vessels with more general utility to a broad range of customers (e.g., FSVs), vessels required for customers to meet regulatory mandates and operating under multiple year contracts or vessels that service customers outside of the offshore oil and natural gas market (e.g., CTVs). For vessel classes and individual vessels with indicators of impairment but not recently impaired as of December 31, 2019, the Company has estimated that their future undiscounted cash flows exceed their current carrying values. The Company’s estimates of future undiscounted cash flows are highly subjective as utilization and rates per day worked are uncertain, including the timing of an estimated market recovery in the offshore oil and natural gas markets and the timing and cost of reactivating cold-stacked vessels. If market conditions decline further, changes in the Company’s expectations on future cash flows may result in recognizing additional impairment charges related to its long-lived assets in future periods. Impairment of 50% or Less Owned Companies. Investments in 50% or less owned companies are reviewed periodically to assess whether there is an other-than-temporary decline in the carrying value of the investment. In its evaluation, the Company considers, among other items, recent and expected financial performance and returns, impairments recorded by the investee and the capital structure of the investee. When the Company determines the estimated fair value of an investment is below carrying value and the decline is other-than-temporary, the investment is written down to its estimated fair value. Actual results may vary from the Company’s estimates due to the uncertainty regarding projected financial performance, the severity and expected duration of declines in value, and the available liquidity in the capital markets to support the continuing operations of the investee, among other factors. Although the Company believes its assumptions and estimates are reasonable, the investee’s actual performance compared with the estimates could produce different results and lead to additional impairment charges in future periods. No impairment charges of investments in 50% or less owned companies were incurred for the year ended December 31, 2019. During the years ended 2018 and 2017, the Company recognized impairment charges of $1.2 million and $8.8 million, respectively, net of tax, related to its 50% or less owned companies (see Note 5). Business Combinations. The Company recognizes 100% of the fair value of assets acquired, liabilities assumed, and noncontrolling interests when the acquisition constitutes a change in control of the acquired entity. Shares issued in consideration for a business combination, contingent consideration arrangements and pre-acquisition loss and gain contingencies are all measured and recorded at their acquisition-date fair value. Subsequent changes to fair value of contingent consideration arrangements are generally reflected in earnings. Acquisition-related transaction costs are expensed as incurred and any changes in an acquirer’s existing income tax valuation allowances and tax uncertainty accruals are recorded as an adjustment to income tax expense. The operating results of entities acquired are included in the accompanying consolidated statements of loss from the date of acquisition (see Note 3). Debt Discount and Issue Costs . Debt discounts and costs incurred in connection with the issuance of debt are amortized over the life of the related debt using the effective interest rate method for term loans and straight-line method for revolving credit facilities and are included in interest expense in the accompanying consolidated statements of loss. Self-insurance Liabilities . The Company maintains marine hull, liability and war risk, general liability, workers compensation and other insurance customary in the industry in which it operates. Both the marine hull and liability policies have annual aggregate deductibles. Marine hull annual aggregate deductibles are accrued as claims are incurred while marine liability annual aggregate deductibles are accrued based on historical loss experience. Exposure to the health benefit plans are limited by maintaining stop-loss and aggregate liability coverage. To the extent that estimated self-insurance losses, including the accrual of annual aggregate deductibles, differ from actual losses realized, the Company’s insurance reserves could differ significantly and may result in either higher or lower insurance expense in future periods. Income Taxes . Deferred income tax assets and liabilities have been provided in recognition of the income tax effect attributable to the book and tax basis differences of assets and liabilities reported in the accompanying consolidated financial statements. Deferred tax assets or liabilities are provided using the enacted tax rates expected to apply to taxable income in the periods in which they are expected to be settled or realized. Interest and penalties relating to uncertain tax positions are recognized in interest expense and administrative and general, respectively, in the accompanying consolidated statements of loss. The Company records a valuation allowance to reduce its deferred tax assets if it is more likely than not that some portion or all of the deferred tax assets will not be realized. 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 be subject to challenges from tax authorities regarding the amount of taxes due for the Company. These challenges may alter the timing or amount of taxable income or deductions. As part of the calculation of income tax expense, the Company determines whether the benefits of its tax positions are at least more likely than not of being sustained based on the technical merits of the tax position. For tax positions that are more likely than not of being sustained, the Company accrues the largest amount of the tax benefit that is more likely than not of being sustained. Such accruals require management to make estimates and judgments with respect to the ultimate outcome of its tax benefits and actual results could vary materially from these estimates. Deferred Gains - Vessel Sale-Leaseback Transactions and Financed Vessel Sales . Prior to the implementation of ASC 842, the Company entered into vessel sale-leaseback transactions with finance companies or provided seller financing on sales of its vessels to third-parties or to 50% or less owned companies. A portion of the gains realized from these transactions was not immediately recognized in income but rather was recorded in the accompanying consolidated balance sheets in deferred gains and other liabilities. In sale-leaseback transactions, gains were deferred to the extent of the present value of future minimum lease payments and were amortized as reductions to rental expense over the applicable lease terms (see Note 7). When the Company determines that future cash inflows do not support future lease cash obligations, the Company records an impairment expense for the amount of the cash flow shortage of all future lease costs, costs to maintain the vessel to the end of the lease term, and costs to return the vessel to its owner, less the amount of any unamortized deferred gains. In financed vessel sales, gains were deferred to the extent that the repayment of purchase notes were dependent on the future operations of the sold vessels and were amortized based on cash received from the buyers. Unamortized deferred gains for four vessels under sale-leaseback agreements were fully recognized as an adjustment to Retained Earnings with the implementation of the new leasing standard (see Note 7). Deferred gain activity related to these transactions for the years ended December 31 was as follows (in

Transformation, Facility Restru

Transformation, Facility Restructuring and Severance Charges	12 Months Ended
	Dec. 31, 2019
Restructuring And Related Activities [Abstract]
Transformation, Facility Restructuring and Severance Charges	2. TRANSFORMATION, FACILITY RESTRUCTURING AND SEVERANCE CHARGES Due to the highly competitive nature of the Company’s business and the continuing losses incurred over the last few years, the Company continues to reduce its overall cost structure and workforce to better align the Company with current activity levels. The ongoing transformation plan, which began in the third quarter of 2019 and is expected to extend through the second quarter of 2020 (the “Transformation Plan”), includes a workforce reduction, organization restructuring, facility consolidations and other cost reduction measures and efficiency initiatives across the Company’s geographic regions. The Transformation Plan was initiated to reduce the Company’s overall cost structure and workforce to better align with current activity levels of oil and gas exploration and production. In connection with the Transformation Plan, the Company recognized o ne-time restructuring charges of $3.3 million and $0.4 million during the third and fourth quarter of 2019. Year-to-date restructuring charges recorded were $3.7 million, The components of restructuring charges year ended December 31, 2019, were as follows (in thousands): United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Latin America Europe (primarily North Sea) Total Transformation Plan Charges Severance $ 2,995 $ — $ 184 $ — $ 200 $ 3,379 Other 307 — 31 1 — 339 Total $ 3,302 $ — $ 215 $ 1 $ 200 $ 3,718 The severance and other restructuring charges gave rise to certain liabilities, the components of which are summarized in the following table (in thousands), and largely relate to liabilities accrued as part of the 2019 Transformation Plan that will be paid pursuant to the respective arrangements and statutory requirements. United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Latin America Europe (primarily North Sea) Total Transformation Plan Severance Liability $ 216 $ — $ — $ — $ 33 $ 249 Other Liability — — — — — — Total Liability $ 216 $ — $ — $ — $ 33 $ 249 The following table is a summary of the cumulative restructuring and reorganization cost incurred in operating charges and the estimated remaining restructuring and reorganization costs to be incurred as of December 31, 2019 (in thousands). 2019 2020 Total One-time termination benefits $ 3,379 $ 2,014 $ 5,393 Professional and other 339 — 339 Total restructuring and reorganization costs incurred and to be incurred $ 3,718 $ 2,014 $ 5,732

Business Acquisitions

Business Acquisitions	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Business Acquisitions	3. BUSINESS ACQUISITIONS Falcon Global Holdings . On February 8, 2018, the Company acquired a 72% controlling interest in Falcon Global Holdings LLC (“FGH”), a joint venture between the Company and Montco Offshore, LLC (“MOI”). The Company and MOI contributed certain liftboat vessels and other related assets to FGH and its designated subsidiaries and assumed certain operating liabilities and indebtedness associated with the liftboat vessels and related assets, including a previous joint venture ("Falcon Global International" or “FGI”) that owned and operated two liftboats. The transaction consolidated the 15 liftboat vessels operated by the Company and six liftboat vessels previously operated by MOI. The total capital contributed to FGH was approximately $112.5 million of which, $43.3 million was transferred from FGI, $18.8 million was contributed by MOI and recorded at fair value, with the remaining capital contributed by the Company. The Company performed a fair value analysis and the purchase price was allocated to the acquired assets and liabilities based on their fair values resulting in no goodwill being recorded Purchase Price Allocation. The allocation of the purchase price for the Company’s acquisitions for the years ended December 31 was as follows (in thousands): 2018 Trade and other receivables $ — Other current assets 211 Investments, at Equity, and Advances to 50% or Less Owned Companies — Property and Equipment 140,257 Accounts payable — Other current liabilities — Long-Term Debt (106,640 ) Other — Minority Interest (18,828 ) Purchase price (1) $ 15,000 (1) The Company did not have any acquisitions requiring purchase price allocation for the year ended December 31, 2019. Purchase price in 2018 was used to pay MOI’s debtor-in-possession obligations.

Equipment Acquisitions and Disp

Equipment Acquisitions and Dispositions	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Equipment Acquisitions and Dispositions	4. EQUIPMENT ACQUISITIONS AND DISPOSITIONS Equipment Additions. The Company’s capital expenditures and payments on equipment were $55.5 million, $51.6 million, and $69.0 million in 2019, 2018 and 2017, respectively. Deliveries of offshore support vessels for the years ended December 31 were as follows: 2019 (1) 2018 2017 FSV 2 — 6 Supply 2 — 5 Liftboat — 6 — CTV 2 2 — 6 8 11 (1) Excludes three FSVs purchased from managed entities, one crew transfer vessel sold upon completion and one ERRV purchased from a joint venture. Equipment Dispositions. For the year ended December 31, 2019, the Company completed the sale of its ERRV fleet business, which consisted of 18 vessels with a net book value of $23.4 million. The net proceeds from the sale of the ERRV fleet, including property and equipment, were approximately $27.4 million resulting in a net loss on dispositions of $9.1 million. Additional consideration of up to £4 million (equivalent to approximately $5.2 million based on the exchange rate at the time of the sale) may be payable to the Company based on revenue targets being achieved in 2020 and 2021. In addition to the sale of the North Sea ERRV fleet, for the year ended December 31, 2019, the Company sold five AHTS vessels, one specialty vessel previously retired and removed from service, seven FSVs, five PSVs, three liftboats, one CTV, one AHTS vessel, and other equipment and one vessel under construction for $59.4 million ($55.1 million cash and $4.3 million in cash deposits previously received) and gains of $6.6 million. During the year ended December 31, 2018, the Company sold property and equipment for net proceeds of $17.4 million $17.3 million in cash and $0.1 million in cash deposits previously received) and recorded gains of $5.7 million, all of which were recognized at the time of sale. In addition, the Company received $4.4 million in deposits on future property and equipment sales. During the year ended December 31, 2017, the Company sold property and equipment for net proceeds of $10.9 million and gains of $3.9 million, all of which were recognized at the time of sale. In addition, the Company received $0.1 million in deposits on future property and equipment sales. Major equipment dispositions for the years ended December 31 were as follows: 2019 (1) 2018 (2) 2017 (3) AHTS 1 1 — FSV 5 9 — Supply 5 — 1 Crew transfer — 1 — Liftboats 3 2 2 14 13 3 (1) Excludes the sale of (i) 18 ERRV vessels from the sale of the Company North Sea Standby Safety business, (ii) one crew transfer vessel to the joint venture FRS Windcat Offshore Logistics, (iii) one FSV to the joint venture OVH, (iv) one FSV to a third party with the Company continuing to manage the vessel, (v) one ERRV from discontinued operations and (vi) six vessels that were previously removed from service (five AHTS vessels and one specialty vessel). (2) Excludes three ERRVs from discontinued operations (3) Excludes one ERRV from discontinued operations.

Investments, at Equity, and Adv

Investments, at Equity, and Advances to 50% or Less Owned Companies	12 Months Ended
	Dec. 31, 2019
Schedule Of Investments [Abstract]
Investments, at Equity, and Advances to 50% or Less Owned Companies	5. Investments, at equity, and advances to 50% or less owned companies as of December 31 were as follows (in thousands): Ownership 2019 2018 MexMar 49.0 % $ 54,249 $ 53,840 SEACOSCO 50.0 % 23,926 28,002 OSV Partners 30.4 % 10,669 11,087 SEACOR Marlin 49.0 % 7,929 7,579 MEXMAR Offshore (1) 49.0 % — 4,900 Offshore Vessel Holdings 49.0 % 4,052 4,900 Dynamic Offshore Drilling 19.0 % — 2,263 Nautical Power 50.0 % — — Other 20.0% — 50.0% 4,396 9,202 $ 105,221 $ 121,773 (1) This joint venture holds the investment in UP Offshore Combined Condensed Financial Information of Other Investees. Summarized financial information of the Company’s other investees, at equity, as of and for the years ended December 31 was as follows (in thousands): 2019 2018 Current assets $ 108,238 $ 99,400 Noncurrent assets 618,745 567,628 Current liabilities 106,742 59,912 Noncurrent liabilities 338,836 325,700 2019 2018 2017 Operating Revenues $ 142,327 $ 109,636 $ 147,360 Costs and Expenses: Operating and administrative 119,767 77,952 78,025 Depreciation 28,800 26,443 30,499 148,567 104,395 108,524 Loss on Asset Dispositions and Impairments, Net (166 ) (89 ) — Operating Income $ (6,406 ) $ 5,152 $ 38,836 Net (Loss) Income(1) $ (36,341 ) $ (13,945 ) $ 13,189 As of December 31, 2019 and 2018, cumulative undistributed net earnings of all 50% or less owned companies included in the Company’s consolidated retained earnings were $16.1 million and $28.5 million, respectively. MexMar. MexMar owns and operates 16 offshore support vessels in Mexico and manages 3 PSV’s and one FSV on behalf of OVH in Mexico. During the year ended December 31, 2019, there were no returns of capital advances or distributions to shareholders. During the year ended December 31, 2018, MexMar returned previously provided capital advances of $9.8 million. During the years ended December 31, 2019, 2018 and 2017 the Company charged $0.3 million of vessel management fees to MexMar. SEACOSCO. On January 17, 2018, the Company announced the formation of SEACOSCO Offshore LLC (“SEACOSCO”), a Marshall Islands entity jointly owned by the Company and China Shipping Fan Tai Limited (“CSFT”) and China Shipping Industry (Hong Kong) Co., Limited (“CSIHK”) each affiliates of COSCO SHIPPING GROUP (“COSCO SHIPPING”). The Company, through SEACOR Offshore Asia LLC, a wholly-owned subsidiary of the Company (“SEACOR Offshore Asia”), owns an unconsolidated 50% interest in SEACOSCO, and CSFT and CSIHK own the other 50% interest in SEACOSCO. SEACOSCO entered into contracts for the purchase of eight Rolls-Royce designed, new construction platform supply vessels (“PSVs”) from COSCO SHIPPING HEAVY INDUSTRY (GUANGDONG) CO., LTD (the “Shipyard”), an affiliate of COSCO SHIPPING for approximately $163.3 million, of which 70% will be financed by the Shipyard, and secured by the PSVs on a non-recourse basis to the Company. SEACOSCO took delivery of two vessels in 2018, five vessels in 2019 and expects to take delivery of the final vessel in the first half of 2020. For the year ended December 31, 2019, and year ended December 31, 2018, the Company contributed capital to SEACOSCO of $2.0 million and $29.6 million, respectively. As the ship manager, the Company is responsible for full commercial, operational, and technical management of the vessels on a worldwide basis. Effective May 31, 2019, SEACOR Offshore Asia, CSFT, CSIHK and the Shipyard, the shipbuilder and lender under deferred payment agreements (“DPAs”) that are secured by the PSVs acquired by SEACOSCO, entered into a Memorandum of Understanding (“MOU”) pursuant to which (i) the Shipyard agreed to not take any action with respect to any existing defaults under the DPAs until August 31, 2019, (ii) SEACOR Offshore Asia was authorized to provide, in its sole discretion, shareholder loans to SEACOSCO and/or its subsidiaries, in an aggregate amount of $13.0 million, in respect of working capital or other payment obligations at an interest rate of 15% per annum and, subject to the priority of the indebtedness under the DPAs, the shareholder loans will have senior priority to any and all other debts of SEACOSCO and/or its subsidiaries, (“SEACOR Shareholder Loans”), (iii) the parties set out the non-binding principal terms and conditions for SEACOR Offshore Asia’s potential acquisition of the 50% interest in SEACOSCO owned by CSFT and CSIHK and (iv) in connection with such acquisition, SEACOR Offshore Asia or its nominee may acquire from the Shipyard two additional PSVs that had been under options held by SEACOSCO. As of December 31, 2019, the balance on the SEACOR Shareholder Loans is $13.0 million, which is the aggregate amount of Shareholder Loans provided, plus capitalized interest of $0.6 million. The Company, as ship manager, has also advanced $2.1 million to SEACOSCO in respect of receivables. As of December 31, 2019, SEACOSCO is in compliance with all debt covenants and is current in all payments. Management remains in discussions with the Shipyard, CSFT and CSIHK with respect to the other transactions contemplated by the MOU. OSV Partners. SEACOR OSV Partners GP LLC and SEACOR OSV Partners I LP (collectively “OSV Partners”) own and operate five offshore support vessels. On September 28, 2018, OSV Partners amended its term loan facility to, among other things, extend its maturity to September 28, 2021, and in connection therewith, the Company participated in a $5.0 million preferred equity offering by OSV Partners and subordinated loan in the amount of $5.0 million issued by OSV Partners, investing $1.1 million in such preferred equity (and committing to invest an additional $1.1 million in such preferred equity if called by the general partner of OSV Partners prior to September 30, 2020) and providing $2.1 million of such loan. On December 18, 2019, the general partner of OSV Partners called the remaining commitments of the Company and other limited partners and the Company satisfied its commitment with an additional $1.1 million investment in such preferred equity. The Company has no further commitments to OSV Partners. On December 23, 2019, OSV Partners further amended its term loan facility to, among other things, provide for interest-only payments during 2020 with the next principal payment due March 31, 2021. The lenders to OSV Partners have no recourse to the Company for outstanding amounts under the facility, and the Company is not obligated to participate in any future investment in or loan any money to OSV Partners. During the year ended December 31, 2017, the Company participated in a $6.0 million preferred equity offering of OSV Partners and invested $2.3 million in support of the venture. For the year ended December 31, 2019, vessel management fees were abated and not charged. For the years ended December 31, 2018 and 2017, the Company received $0.6 million, of vessel management fees from OSV Partners for each year. SEACOR Marlin. SEACOR Marlin LLC (“SMLLC”) own and operate Seacor Marlin supply vessel. On September 13, 2018, the Company sold 51% of SMLLC to MOMI, a wholly-owned subsidiary of MexMar, for $8.0 million in cash, which generated a gain of $0.4 million. The Seacor Marlin supply vessel was pledged as collateral under the MexMar credit facility, for which the Company receives an annual collateral fee. MEXMAR Offshore. On December 20, 2018, UP Offshore (Bahamas) Ltds (“UP Offshore”), a provider of offshore support vessel services to the energy industry in Brazil, was acquired by MEXMAR Offshore, a new joint venture company that is 49% owned by the Company, and 51% owned by a subsidiary of CME. MEXMAR Offshore acquired UP Offshore for nominal consideration, re-financed its existing debt to fund capital expenditures on two vessels and a $10.0 million loan to fund new working capital requirements. As of December 31, 2019, UP Offshore’s 13 vessel fleet, 10 vessels were located and registered in Brazil and two were located and registered in Mexico. During the year ended December 31, 2019, UP Offshore sold one PSV to a third party and repositioned three PSV’s to Mexico. Offshore Vessel Holdings. On December 28, 2018, the Company invested $4.9 million for a 49% interest in Offshore Vessel Holdings SAPI de CV (“OVH”), the remaining 51% is owned by a subsidiary of CME. OVH invests in offshore assets and charters marine equipment. During the year ended December 31, 2019 OVH loaned $10.0 million to Operadora Productura Mexsicana, a drilling company in Mexico which owns and operates two jackup drilling rigs (“OPM”), chartered in three PSV’s from UP Offshore and purchased one FSV from the Company for $2.4 million through a seller’s finance agreement. 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 quarter of 2013. During the year ended December 31, 2017, the Company recognized an impairment charge of $8.3 million, net of tax, for an-other-than-temporary decline in the fair value of its equity investment upon Dynamic Offshore Drilling’s unsuccessful bid on a charter renewal with a customer. During the year ended December 31, 2018, the Company recognized equity losses in Dynamic Offshore Drilling of $2.0 million. During 2019, the Company recorded additional losses of $2.3 million which lowered the investment value to zero. Nautical Power. During the quarter ended September 30, 2018, the joint venture repaid the Company’s $6.4 million investment in Nautical Power, LLC (“Nautical Power”) in cash. Falcon Global. Falcon Global was formed to construct and operate two foreign-flag liftboats. During the three months ended March 31, 2017, the Company and its partner each contributed additional capital of $0.4 million, and the Company made working capital advances of $2.0 million to Falcon Global. In March 2017, the Company’s partner declined to participate in a capital call from Falcon Global and, as a consequence, the Company obtained 100% voting control of Falcon Global in accordance with the terms of the operating agreement. On February 8, 2018, 100% of the equity interests of Falcon Global were contributed to FGH and its designated subsidiaries as part of the formation of the FGH joint venture. Sea-Cat Crewzer II. Sea-Cat Crewzer II owns and operates two high-speed offshore catamarans. On April 28, 2017, the Company acquired a 100% controlling interest in Sea-Cat Crewzer II through the acquisition of its partners’ 50% ownership interest for $11.3 million in cash. Sea-Cat Crewzer. Sea-Cat Crewzer owns and operates two high-speed offshore catamarans. On April 28, 2017, the Company acquired a 100% controlling interest in Sea-Cat Crewzer through the acquisition of its partners’ 50% ownership interest for $4.4 million in cash. Other. The Company’s other 50% or less owned companies own and operate five vessels. During the year ended December 31, 2019, the Company received dividends of $2.1 million and $0.5 million of return capital from these 50% or less owned companies. During the year ended December 31, 2018, the Company recognized impairment charges of $1.2 million, net of tax, to reduce its investment carrying value in a certain 50% or less owned company to zero. During the year ended December 31, 2017, the Company received dividends of $2.6 million, made capital contributions and advances of $0.8 million and received repayments on advances of $0.2 million with these 50% or less owned companies. In addition, during the year ended December 31, 2017, the Company recognized impairment charges of $0.5 million, net of tax, for an other-than-temporary decline in the fair value of its investment in a certain 50% or less owned company. During the years ended December 31, 2019, the Company received less than $0.1 million of vessel management fees from these 50% or less owned companies. In the years ended December 31, 2018 and 2017, the Company received $0.3 million, and $0.7 million, respectively.

Construction Reserve Funds

Construction Reserve Funds	12 Months Ended
	Dec. 31, 2019
Restricted Cash And Investments [Abstract]
Construction Reserve Funds	6. The Company has established, pursuant to Section 511 of the Merchant Marine Act, 1936, as amended, construction reserve fund accounts subject to agreements with the Maritime Administration. In accordance with this statute, the Company is permitted to deposit proceeds from the sale of certain vessels into the construction reserve fund accounts and defer the taxable gains realized from the sale of those vessels. Qualified withdrawals from the construction reserve fund accounts are only permitted for the purpose of acquiring qualified U.S.-flag vessels as defined in the statute and approved by the Maritime Administration. To the extent that sales proceeds are reinvested in replacement vessels, the carryover depreciable tax basis of the vessels originally sold is attributed to the U.S.-flag vessels acquired using such qualified withdrawals. The construction reserve funds must be committed for expenditure within three years of the date of sale of the equipment, subject to two one-year extensions that can be granted at the discretion of the Maritime Administration or be released for the Company’s general use as nonqualified withdrawals. For nonqualified withdrawals, the Company is obligated to pay taxes on the previously deferred gains at the prevailing statutory tax rate plus penalties and interest thereon for the period such taxes were deferred. As of December 31, 2019, 2018 and 2017, the Company’s construction reserve funds are classified as non-current assets in the accompanying consolidated balance sheets as the Company has the intent and ability to use the funds to acquire equipment. Construction reserve fund transactions for the years ended December 31 were as follows (in thousands): 2019 2018 2017 Withdrawals $ (15,168 ) $ (17,300 ) $ (39,163 ) Deposits — — 6,315 $ (15,168 ) $ (17,300 ) $ (32,848 )

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	7. LEASES On February 25, 2016, the FASB issued a comprehensive new leasing standard, ASC 842, Leases, As of December 31, 2019, the Company leases in three AHTS vessels, two liftboats, one FSV and certain facilities and other equipment. The leases typically contain purchase and renewal options or rights of first refusal with respect to the sale or lease of the equipment. As of December 31, 2019, the remaining lease terms of the vessels have remaining durations from 11 to 23 months. The lease terms of the other equipment range in duration from one to 324 months. As of December 31, 2019, future minimum payments for operating leases for the years ended December 31 were as follows (in thousands): 2020 $ 15,355 2021 7,128 2022 668 2023 621 2024 696 Years subsequent to 2024 4,437 28,905 Interest component (3,984 ) 24,921 Current portion of long-term operating lease liabilities 15,099 Long-term operating lease liabilities $ 9,822 For the year ended December 31, 2019, the components of lease expense were as follows (in thousands): 2019 Operating lease expense $ 13,639 Short-term lease expense (lease duration of twelve months or less at lease commencement) 2,519 $ 16,158 For the year ended December 31, 2019, other information related to operating leases were as follows (in thousands except weighted average data): 2019 Operating cash flows from operating leases $ 19,339 Right-of-use assets obtained for operating lease liabilities $ 35,246 Weighted average remaining lease term, in years 4.7 Weighted average discount rate 4.1 % 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 $5.3 million for one such lease for the year ended December 31, 2019 and $6.8 million for three such leases for the year ended December 31, 2018. A liability was recorded to reflect the amount of future lease payments, expenses required to maintain the vessels, and expenses required to return the vessels to their owners at the end of the lease term, offset by unamortized deferred gain on the sale-leaseback of the vessels.

Long Term Debt

Long Term Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Long Term Debt	8. The Company’s long-term debt obligations as of December 31 were as follows (in thousands): 2019 2018 Convertible Senior Notes $ 125,000 $ 125,000 SEACOR Marine Foreign Holdings Loan Facility 113,750 126,750 Falcon Global USA Term Loan Facility 102,349 109,099 Sea-Cat Crewzer III Term Loan Facility 24,128 25,989 Windcat Workboats Facilities 24,730 24,850 Falcon Global USA Revolver 15,000 15,000 SEACOR 88/888 Term Loan 11,000 11,000 SEACOR Alps 10,534 — BNDES Equipment Construction Finance Notes 3,332 5,284 429,823 442,972 Portion due within one year (17,802 ) (16,812 ) Debt discount (26,343 ) (32,005 ) Issue costs (5,427 ) (6,301 ) $ 380,251 $ 387,854 The Company’s contractual long-term debt maturities for the years ended December 31 were as follows (in thousands): 2020 $ 17,802 2021 51,789 2022 26,007 2023 231,674 2024 90,800 Years subsequent to 2024 11,752 $ 429,823 As of December 31, 2019, the Company is in compliance with all debt covenants and lender requirements. SEACOR ALPS On September 30, 2019, the Company took possession of the SEACOR Alps, a Rolls Royce UT771CDL designed diesel electric powered PSV of 3,800 tons deadweight capacity with dynamic position class 2 and firefighting class 1 notations. As part of this transaction, the shipbuilder financed 70% of the total purchase price pursuant to a deferred payment agreement. This loan bears interest at 5% and is due and payable in 2023. SEACOR Marine Foreign Holdings . On September 26, 2018, SEACOR Marine Foreign Holdings Inc. (“SMFH”), a wholly-owned subsidiary of the Company, entered into a $130.0 million loan facility with a syndicate of lenders administered by DNB Bank ASA (the “SMFH Loan Facility”). Subject to Amendment No. 1 and Amendment No. 2 described below, SMFH’s obligations pursuant to the SMFH Loan Facility were initially secured by mortgages on 20 vessels owned by the Company’s vessel owning subsidiaries as well as an assignment of earnings from those subsidiaries. The loan matures in 2023 and bears interest at a variable rate based on LIBOR (currently 5.875%). The obligations of SMFH under the SMFH Loan Facility are guaranteed by SEACOR Marine (the “SMFH Loan Facility Guaranty”). The proceeds from the SMFH Loan Facility were used to pay off all obligations under other credit facilities of subsidiaries of the Company (Falcon Global International Term Loan Facility, Sea-Cat Crewzer II Term Loan Facility, Sea-Cat Crewzer Term Loan Facility and C-Lift Acquisition Notes totaling $101.3 million, consisting of $99.9 million principal and $1.4 million accrued interest), resulting in a net increase in term debt of $30.1 million. Principal payments of $3.3 million per quarter under the SMFH Loan Facility began in December 2018. As a result of this transaction, the Company recognized a loss of $0.6 million upon the extinguishment of debt. In October 2018, the Company entered into an interest rate swap agreement on the notional value at inception of $65.0 million related to this debt. The SMFH Loan Facility provides for customary events of default and has customary affirmative and negative covenants for transactions of this type that are applicable to SEACOR Marine, SMFH and its subsidiaries. On August 6, 2019, SEACOR Marine, SMFH, and certain vessel-owning subsidiaries of SEACOR Marine, entered into Amendment No. 1 to the SMFH Loan Facility and SMFH Loan Facility Guaranty (the “Amendment No. 1”), which provided for, among other things, (i) the release of one vessel from a mortgage securing the SMFH Loan Facility and the substitution of mortgages over two other vessels owned by vessel-owning subsidiaries of SEACOR Marine, and (ii) the modification of certain financial maintenance and restrictive covenants contained in the SMFH Loan Facility or the SMFH Loan Facility Guaranty, including with respect to asset maintenance, vessel collateral releases, EBTIDA coverage ratios and the payment of dividends and distributions. On November 26, 2019, SEACOR Marine, SMFH, and certain vessel-owning subsidiaries of SEACOR Marine, entered into Amendment No. 2 to the SMFH Loan Facility, as amended by Amendment No. 1 (the “Amendment No. 2”), which provided for, among other things, (i) the release of six vessels from mortgages securing the Credit Facility and the substitution of mortgages over three other vessels owned by vessel-owning subsidiaries of SEACOR Marine and (ii) the bareboat registration in Nigeria of a vessel subject to a mortgage securing the Credit Facility. OSV Partners. SEACOR OSV Partners GP LLC and SEACOR OSV Partners I LP (collectively “OSV Partners”) own and operate five offshore support vessels. On September 28, 2018, OSV Partners amended its term loan facility to, among other things, extend its maturity to September 28, 2021, and in connection therewith, the Company participated in a $5.0 million preferred equity offering by OSV Partners and subordinated loan in the amount of $5.0 million issued by OSV Partners, investing $1.1 million in such preferred equity (and committing to invest an additional $1.1 million in such preferred equity if called by the general partner of OSV Partners prior to September 30, 2020) and providing $2.1 million of such loan. On December 18, 2019, the general partner of OSV Partners called the remaining commitments of the Company and other limited partners and the Company satisfied its commitment with an additional $1.1 million investment in such preferred equity. The Company has no further commitments to OSV Partners. On December 23, 2019, OSV Partners further amended its term loan facility to, among other things, provide for interest-only payments during 2020 with the next principal payment due March 31, 2021. The lenders to OSV Partners have no recourse to the Company for outstanding amounts under the facility, and the Company is not obligated to participate in any future investment in or loan any money to OSV Partners. During the year ended December 31, 2017, the Company participated in a $6.0 million preferred equity offering of OSV Partners and invested $2.3 million in support of the venture. No management fees were charged to OSV Partners for the year ended December 31, 2019, as management fees were abated. For the years ended December 31, 2018 and 2017, the Company received $0.6 million, of vessel management fees from OSV Partners for each year. Convertible Senior Notes. On December 1, 2015, the Company issued $175.0 million in aggregate principal amount of its Convertible Senior Notes (the “Convertible Senior Notes”), at an interest rate of 3.75%, initially due December 1, 2022, (subsequently amended to December 2, 2023 as described below) to investment funds managed and controlled by the Carlyle Group (collectively “Carlyle”). The Convertible Senior Notes are convertible into shares of Common Stock at a conversion rate of 23.26 shares per $1,000 in principal amount of such notes, subject to certain conditions, or, into Warrants to purchase an equal number of shares of Common Stock at an exercise price of $0.01 per share in order to facilitate the Company’s compliance with the provisions of the Jones Act. The indenture governing the Convertible Senior Notes contains customary events of default with respect to the Convertible Senior Notes. Upon completion of the Spin-off, the Company bifurcated the embedded conversion option liability of $27.3 million from the Convertible Senior Notes and recorded an additional debt discount (see Notes 10 and 11). The adjusted unamortized debt discount and issue costs are being amortized as additional non-cash interest expense over the remaining maturity of the debt for an overall effective interest rate of 7.95% and the changes in the fair value of the bifurcated derivative are recorded as derivative income or loss. On May 2, 2018, the Company and Carlyle entered into an exchange transaction (the “Exchange”) pursuant to which Carlyle exchanged $50 million in principal amount of the Convertible Senior Notes for Warrants to purchase 1,886,792 shares of Common Stock (to facilitate compliance with the provisions of the Jones Act) at an exercise price of $0.01 per share, subject to adjustments (the “Carlyle Warrants”), representing an implied exchange rate of approximately 37.73 shares per $1,000 in principal amount of the Convertible Senior Notes (equivalent to an exchange price of $26.50 per share). The Carlyle Warrants have a 25-year term, which commenced May 2, 2018. The Company and Carlyle also amended the $125.0 million in principal amount of Convertible Senior Notes that remained outstanding following the Exchange to (i) increase the interest rate from 3.75% per annum to 4.25% per annum and (ii) extend the maturity date of the Convertible Senior Notes by 12 months to December 1, 2023. Interest on the Convertible Senior Notes is payable semi-annually on June 15 and December 15 of each year. Falcon Global USA. On February 8, 2018, a wholly-owned subsidiary of SEACOR Marine and MOI formed and capitalized a joint venture named Falcon Global Holdings LLC. In connection therewith and MOI’s plan of reorganization, which was confirmed on January 18, 2018, MOI emerged from its Chapter 11 bankruptcy case. In accordance with the terms of a Joint Venture Contribution and Formation Agreement, the Company and MOI contributed certain liftboat vessels and other related assets to FGH and its designated subsidiaries and FGH and its designated subsidiaries assumed certain operating liabilities and indebtedness associated with the liftboat vessels and related assets. On February 8, 2018, Falcon Global USA LLC (“FGUSA”), a wholly-owned subsidiary of FGH, paid $15.0 million of MOI’s debtor-in-possession obligations and entered into a $131.1 million credit agreement comprised of a $116.1 million term loan (the “FGUSA Term Loan”) and a $15.0 million revolving loan facility (the “FGUSA Revolving Loan Facility”) bearing interest at a variable rate (currently 6.3125%), maturing in 2024 and secured by 15 vessels owned by wholly-owned subsidiaries of FGUSA (collectively, the “FGUSA Credit Facility”). The full amount of the FGUSA Term Loan and other amounts paid by affiliates of MOI satisfied in full the amounts outstanding under MOI’s pre-bankruptcy petition credit facilities. In connection with the FGUSA Credit Facility, SEACOR Marine issued a limited obligation guaranty, dated February 8, 2018, pursuant to which SEACOR Marine guaranteed certain interest payments and participation fees under the FGUSA Credit Facility until February 8, 2020 (the “Guaranty”). Except as provided in the Guaranty, the FGUSA Credit Facility, is non-recourse to SEACOR Marine and its subsidiaries other than FGUSA. The Company performed a fair market valuation of the debt reflecting a debt discount of $10.0 million, which will be amortized over the life of the FGUSA Credit Facility. During the year ending December 31, 2018, the Company borrowed $15.0 million under the FGUSA Revolving Loan Facility for working capital purposes and made principal payments of $7.0 million under the term loan facility after sale of two collateralized vessels. The Company consolidates FGH as the Company holds 72% of the equity interest in FGH and is entitled to appoint a majority of the board of managers of FGH. Sea-Cat Crewzer III Term Loan Facility. On April 21, 2016, Sea-Cat Crewzer III LLC (“Sea-Cat Crewzer III”) entered into a €27.6 million term loan facility (payable in U.S. dollars) secured by the vessel owned by Sea-Cat Crewzer III and fully guaranteed by SEACOR Marine (the “Sea-Cat Crewzer III Loan Facility”). Borrowings under the facility bear interest at a Commercial Interest Reference Rate, currently 2.76%. During the years ended December 31, 2017 and 2016, Sea-Cat Crewzer III drew $7.1 million and $22.8 million, respectively, under the facility and incurred issue costs of $2.7 million in 2016 related to this facility. During the years ended December 31, 2018 and 2017, Sea-Cat Crewzer III made scheduled payments of $3.1 million and $0.6 million, respectively, related to this facility. On December 26, 2019, Sea-Cat Crewzer III, SEACOR Marine, Banco Santander S.A. (as mandated lead arranger and agent), and Santander Bank, N.A. (as lender) entered into Amendment No. 1 to the Sea-Cat Crewzer III Loan Facility, which provided for, among other things, an increase to the maximum debt to capitalization ratio required to be maintained thereunder. Windcat Workboats Facilities. On May 24, 2016, Windcat Workboats entered into a €25.0 million revolving credit facility secured by 38 of the Company’s CTV fleet. Borrowings under the facility bear interest at variable rates based on EURIBOR plus a margin ranging from 3.00% to 3.30% per annum plus mandatory lender costs and mature in 2021. The Company is currently in negotiations to extend the maturity to 2022. A quarterly commitment fee is payable based on the unfunded portion of the commitment amount at rates ranging from 1.20% to 1.32% per annum. During the year ended December 31, 2016, Windcat Workboats drew $23.5 million (€21.0 million) under the facility to repay all of its then outstanding debt totaling $22.9 million and incurred issuance costs of $0.6 million related to this facility. During the year ended December 31, 2018, the Company converted €6.0 million denominated debt to pound sterling denominated debt, paying off approximately $7.5 million in euro denominated debt and borrowing approximately $8.5 million in pound sterling denominated debt, resulting in a net increase in USD borrowings of $1.0 million to be used for future capital commitments. SEACOR 88/888. On July 5, 2018, a wholly-owned subsidiary of SEACOR Marine entered into a new term loan of $11.0 million and used the funds to acquire two vessels that were previously managed (but not owned) by the Company. The term loan matures in 2023, bears interest at a variable rate (currently 5.5625%) and is secured by the two vessels. SEACOR Marine provided a limited guaranty of such loan under which claims recoverable from SEACOR Marine shall not exceed the lesser of (x) $5.5 million and (y) 50% of the obligations outstanding at the time a claim is made thereunder. In October 2018, the Company entered into an interest rate swap agreement on the notional value at inception of $5.5 million related to this loan. BNDES Equipment Construction Finance Notes. The Company financed the construction of two offshore support vessels in Brazil with Banco Nacional de Desenvolvimento Economico e Social (“BNDES”), a Brazilian government-owned entity. The notes are secured by a first mortgage on these vessels and guaranteed by SEACOR Holdings. The notes bear interest at 4.00% per annum, require monthly principal and interest payments, and mature in July through October 2021. During the years ended December 31, 2019, 2018 and 2017, the Company made scheduled payments of $2.0 million, $2.0 million and $2.0 million, respectively. Falcon Global International Term Loan Facility. On August 3, 2015, Falcon Global International entered into a term loan facility to finance the construction of two foreign-flag liftboats. The facility consisted of two tranches: (i) a $62.5 million facility to fund the construction costs of the liftboats (“Tranche A”) and (ii) a $18.0 million facility for certain project costs (“Tranche B”). The facility was secured by the liftboats and is repayable over a five-year period that began after the completion of the construction of the liftboats and matures June 30, 2022. On November 3, 2017, Falcon Global International executed an amendment to its term loan facility, at a cost of $0.2 million, that required Falcon Global to maintain a debt service coverage ratio and a minimum cash balance on hand in excess of defined thresholds. In addition, the amendment required SEACOR Marine, as guarantor, to maintain a debt to capital ratio below a defined threshold and a minimum cash balance on hand in excess of a defined threshold. In March 2017, the Company’s partner declined to participate in a capital call from Falcon Global International and, as a consequence, the Company obtained 100% voting control of Falcon Global International in accordance with the terms of the operating agreement. The Company consolidated into its financial statements Falcon Global International’s then outstanding debt under this facility of $58.3 million, net of issue costs of $1.0 million, effective March 31, 2017 (see Note 5). During April 2017, the Tranche B facility was canceled prior to any funding. During the nine months ended December 31, 2017, Falcon Global made scheduled payments of $4.4 million under Tranche A. During the year ended December 31, 2018, Falcon Global International made scheduled payments of $3.0 million. The remaining principal balance of $51.9 million was paid off with the proceeds of SEACOR Marine Foreign Holdings Syndicated Facility on September 28, 2018. Sea-Cat Crewzer II Term Loan Facility. On April 28, 2017, the Company acquired a 100% controlling interest in Sea-Cat Crewzer II through the acquisition of its partners’ 50% ownership interest (see Notes 3 and 5). Sea-Cat Crewzer II had a term loan facility that matured in 2019 which was secured by a first preferred mortgage on its vessels. On December 19, 2017, Sea-Cat Crewzer II executed an amendment, at a cost of $0.1 million, that replaced SEACOR Holdings with SEACOR Marine as guarantor and required SEACOR Marine to maintain a debt to capital ratio below a defined threshold and a minimum cash balance on hand in excess of a defined threshold. The facility called for quarterly payments of principal and interest with a balloon payment of $17.3 million due at maturity. The interest rate was fixed at 1.52%, inclusive of an interest rate swap, plus a margin ranging from 2.10% to 2.75% subject to the level of funded debt (overall rate of 5.64% as of December 31, 2017). In the year ended December 31, 2017, the Company made scheduled payments of $1.2 million. During the year ended December 31, 2018, Sea-Cat Crewzer II made scheduled payments of $1.8 million. The remaining principal balance of $19.1 million was paid off by the SEACOR Marine Foreign Holdings Syndicated Facility on September 28, 2018. Sea-Cat Crewzer Term Loan Facility. On April 28, 2017, the Company acquired a 100% controlling interest in Sea-Cat Crewzer through the acquisition of its partners’ 50% ownership interest (see Notes 3 and 5). Sea-Cat Crewzer had a term loan facility that matures in 2019 which was secured by a first preferred mortgage on its vessels. On December 19, 2017, Sea-Cat Crewzer executed an amendment, at a cost of $0.1 million, that replaced SEACOR Holdings with SEACOR Marine as guarantor and required SEACOR Marine to maintain a debt to capital ratio below a defined threshold and a minimum cash balance on hand in excess of a defined threshold. The facility called for quarterly payments of principal and interest with a balloon payment of $15.3 million due at maturity. The interest rate was fixed at 1.52%, inclusive of an interest rate swap, plus a margin ranging from 2.10% to 2.75% subject to the level of funded debt (overall rate of 5.64% as of December 31, 2017). In the year ended December 31, 2017, the Company made scheduled payments of $1.1 million. During the year ended December 31, 2018, Sea-Cat Crewzer made scheduled payments of $1.6 million. The remaining principal balance of $16.9 million was paid off by the SEACOR Marine Foreign Holdings Syndicated Facility on September 28, 2018. Letters of Credit. As of December 31, 2019, the Company had outstanding letters of credit totaling $0.5 million for one lease obligation and labor and performance guarantees.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	9. INCOME TAXES In late 2017, the U.S. Tax Cuts and Jobs Act (the “Tax Act”) was enacted into law. This law significantly impacted our corporate income taxes commencing in 2018 and will continue to do so in future years. The most significant provisions included reducing the corporate tax rate from 35% to 21%; eliminating U.S. federal tax on dividends from foreign subsidiaries, creating a limitation on deductible interest expense, further restricting the compensation deduction, and changing the utilization of Net Operating Losses (“NOL’s”). In arriving at the 2019 results the Company took into account the impacts of the Tax Act based on our interpretation of the provisions enacted and the proposed regulations issued as of this date Loss before income tax benefit and equity in earnings (losses) of 50% or less owned companies derived from U.S. and foreign companies for the years ended December 31 were as follows (in thousands): 2019 2018 2017 United States $ (71,833 ) $ (72,540 ) $ (90,696 ) Foreign (22,025 ) (29,466 ) (45,879 ) Eliminations 11,022 8,782 18,785 $ (82,836 ) $ (93,224 ) $ (117,790 ) The components of income tax expense (benefit) for the years ended December 31 were as follows (in thousands): 2019 2018 2017 Current: Federal $ (6 ) $ 5,987 $ (16,705 ) State (78 ) 3 (42 ) Foreign 5,039 3,393 3,343 4,955 9,383 (13,404 ) Deferred: Federal (12,594 ) (21,466 ) (60,750 ) State (224 ) (1,404 ) (172 ) Foreign (49 ) 133 (84 ) (12,867 ) (22,737 ) (61,006 ) $ (7,912 ) $ (13,354 ) $ (74,410 ) For the year ending December 31, 2019, the Company has recorded a return to provision adjustment related to losses from a consolidated joint venture for the 2018 tax year. The resulting additional liability of $2.3 million was recorded in the Company’s financial statements during the third quarter of 2019. For 2018, the Company incurred a current tax liability of $1.4 million related to the non-qualified withdrawal of funds from a Capital Construction Fund (“CCF”) by a partnership in which the Company held a 50% interest. The Company had previously recorded a deferred tax liability in connection with this CCF fund. As of December 31, 2017, the Company’s net operating loss carryforwards excluded potential tax benefits of $3.9 million as a result of uncertainty regarding interpretation of the Tax Act. Subsequent guidelines have confirmed that the Company should recognize the tax benefits of $3.9 million and therefore, for the year ending December 31, 2018, the Company removed the uncertain tax position previously established against the net operating loss carryforwards. During the preparation of the 2017 federal income tax return, the Company’s management realized that they had overestimated the available foreign taxes that could be credited against the 2017 transition tax. This resulted in an additional tax liability of $3.4 million on its 2017 federal income tax return. This additional liability was recorded as a return-to-provision adjustment to tax expense during the year ended December 31, 2018. 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: 2019 2018 2017 Statutory rate (21.0 )% (21.0 )% (35.0 )% U.S. federal income tax law changes — % — % (37.3 )% SEACOR Holdings share awards to Company personnel — % 0.2 % 2.3 % Non-deductible expenses — % — % 1.8 % Exclusion of foreign subsidiaries with accumulated losses and withholding tax 7.2 % 9.5 % 3.1 % Noncontrolling interests 1.8 % (1.5 )% 1.7 % State taxes (0.3 )% (1.5 )% (0.2 )% Return to provision 2.9 % (0.5 )% 0.4 % Other (0.2 )% 0.5 % — % Effective Tax Rate (9.6 )% (14.3 )% (63.2 )% For the year ending December 31, 2019, the Company’s effective income tax rate of 9.6% was lower than the statutory tax rate of 21% primarily due to foreign subsidiaries with current losses for which there is no current or future federal income tax benefit, reducing the statutory tax rate by 7.2%, and noncontrolling interests reducing the tax rate by 1.8% For the year ending December 31, 2018, the Company’s effective income tax rate of 14.3% was lower than the Company’s statutory tax rate of 21% primarily due to foreign subsidiaries with current losses for which there is no current or future federal income tax benefit. For the year ending December 31, 2017, the Company’s effective income tax rate of 63.2% was higher than the Company’s statutory tax rate of 35% primarily due to income tax benefits of $43.7 million recognized as a result of the Tax Act. The majority of the income tax benefits recognized were due to a reduction in U.S. tax rates from 35% to 21% applied to the Company’s domestic basis differences and the elimination of previously accrued deferred taxes on the unremitted earnings of the Company’s foreign subsidiaries. The components of net deferred income tax liabilities as of December 31 were as follows (in thousands): 2019 2018 Deferred tax liabilities: Property and equipment $ 63,827 $ 65,880 Investments in 50% or Less Owned Companies 3,039 3,040 Other 10,953 7,792 Total deferred tax liabilities 77,819 76,712 Deferred tax assets: Federal Net Operating Loss Carryforwards 28,664 20,974 Other 16,561 11,677 45,225 32,651 Valuation Allowance (1,311 ) (624 ) Total deferred tax assets 43,914 32,027 Net deferred tax liabilities $ 33,905 $ 44,685 The Section 163(j) interest deduction limitations were amended to limit the ability of the Company to deduct net interest expense to thirty percent of adjusted taxable income. For the year ended December 31, 2019, $6.6 million of interest expense was suspended, and for the year ended December 31, 2018, $3.6 million of interest expense was suspended, resulting in a total interest expense amount available for carry forward of $10.2 million. This amount will be available to be deducted in future years subject to the 30% limitation. Future utilization of NOL’s arising in tax years after December 31, 2017 are limited to eighty percent of taxable income and are allowed to be carried forward indefinitely. As of December 31, 2019, the Company has $42.2 million of net operating losses generated prior to December 31, 2017 and $94.5 million of net operating losses generated after 2017. Net operating losses generated in 2017 may carry forward 20 years (expiring in 2037). The 2018 and 2019 NOLs will carry forward indefinitely with no expiration period but its utilization will be subject to an annual 80 percent of taxable income limitation. As of December 31, 2019, the Company's valuation allowance of $1.3 million related primarily to Louisiana state net operating loss carryforwards.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Strategies	12 Months Ended
	Dec. 31, 2019
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Strategies	10. 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 were as follows (in thousands): 2019 2018 Balance Sheet Classification Derivative Asset Derivative Liability Derivative Asset Derivative Liability Derivatives designated as hedging instruments: Interest rate swap agreements (cash flow hedges) Current $ — $ 3,009 $ — $ 1,659 — 3,009 — 1,659 Derivatives not designated as hedging instruments: Conversion option liability on Convertible Senior Notes Long-Term — 5,205 — 5,276 $ — $ 8,214 $ — $ 6,935 Fair Value Hedges. From time to time, the Company may designate certain of its foreign currency exchange contracts as fair value hedges in respect of capital commitments denominated in foreign currencies. By entering into these foreign currency exchange contracts, the Company may fix a portion of its capital commitments denominated in foreign currencies in U.S. dollars to protect against currency fluctuations. During the year ended December 31, 2017, the Company recognized gains of $0.1 million on these contracts which were recognized to the corresponding hedged equipment included in construction in progress in the accompanying consolidated balance sheets. Cash Flow Hedges. The Company and certain of its 50% or less owned companies have interest rate swap agreements designated as cash flow hedges at their inception. By entering into these interest rate swap agreements, the Company and its 50% or less owned companies have converted the variable LIBOR or EURIBOR component of certain of their outstanding borrowings to a fixed interest rate. The Company recognized losses on derivative instruments designated as cash flow hedges of $1.3 million for the year ended December 31, 2019, gains of $1.6 million for the year ended December 31, 2018 and losses of $0.2 million for the year ended December 31, 2017 as a component of other comprehensive loss. As of December 31, 2019, the interest rate swaps held by the Company and certain of the Company’s 50% or less owned companies were as follows: • Windcat Workboats had two interest rate swap agreements maturing in 2021 that call for the Company to pay a fixed rate of interest of (0.03%) plus margin on the aggregate notional value of €15.0 million ($16.8 million) and receive a variable interest rate based on EURIBOR on the aggregate notional value; • SEACOR Marine Foreign Holdings had an interest rate swap agreement maturing in 2023 that calls for SMFH to pay a fixed rate of interest of 3.32% plus margin on the amortized notional value of $8.8 million and receive a variable interest rate based on LIBOR on the amortized notional value; • SEACOR Marine Foreign Holdings had an interest rate swap agreement maturing in 2023 that calls for SMFH to pay a fixed rate of interest of 3.195% plus margin on the amortized notional value of $48.6 million and receive a variable interest rate based on LIBOR on the amortized notional value; and • SEACOR 88/888 had an interest rate swap agreement maturing in 2023 that calls for Seacor 88/888 to pay a fixed rate of interest of 3.175% plus margin on the amortized notional value of $5.5 million and receive a variable interest rate based on LIBOR on the amortized notional value. Derivative Instruments. The Company utilizes derivative instruments to manage the volatility of cash flows due to fluctuating interest rates. All derivative instruments not qualifying for the normal purchase and normal sale exception are recorded on the balance sheets at fair value. The treatment of the periodic changes in fair value will depend on whether the derivative is designated and effective as a hedge for accounting purposes. 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 qualify as a hedge or is not designated as a hedge, the gain or loss resulting from the change in fair value on the derivative is recognized currently in earnings as a component of other income (expense). 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 longer probable that a hedged forecasted transaction will occur, deferred gains or losses on the hedging instrument are reclassified to earnings immediately. 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% or less owned companies are also reported as a component of the Company’s other comprehensive loss in proportion to the Company’s ownership percentage, with reclassifications and ineffective portions being included in equity in earnings (losses) of 50% or less owned companies, net of tax, in the accompanying consolidated statements of loss. 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 $8.2 million as of December 31, 2019. The estimated fair value is net of an adjustment for credit risk based on the default probabilities by year as indicated by market quotes for the counterparties’ credit default swap rates. The credit risk adjustment was immaterial for all periods presented. 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 2019 2018 2017 Interest rate swap contracts $ (1,901 ) $ (1,939 ) $ 214 Joint venture interest rate swap contracts (645 ) (76 ) 389 Gain (Loss) Reclassified from OCI into Income (Effective Portion) Location of Gain 2019 2018 2017 Interest expense $ 552 $ 31 118 Our consolidated earnings are also affected by the use of the mark-to-market method of accounting for derivative instruments that do not qualify for hedge accounting or that have not been designated as hedges. The changes in fair value of these instruments are recorded on the balance sheet and through earnings rather than being deferred until the anticipated transaction settles. The use of mark-to-market accounting for financial instruments can cause non-cash earnings volatility due to changes in the underlying commodity price indices. Other Derivative Instruments. The Company recognized gains (losses) on derivative instruments not designated as hedging instruments for the years ended December 31 as follows (in thousands): Derivative gains (losses), net 2019 2018 2017 Conversion option liability on Convertible Senior Notes $ 71 $ 1,556 $ 20,422 Interest rate swap agreements — 1,298 46 Forward currency exchange, option and future contracts — — (212 ) $ 71 $ 2,854 $ 20,256 The conversion option liability relates to the bifurcated embedded conversion option in the Convertible Senior Notes (See Note 8). The Company and certain of the Company’s 50% or less owned companies have entered into interest rate swap agreements for the general purpose of providing protection against increases in interest rates, which might lead to higher interest costs. As of December 31, 2019, the interest rate swaps held by the Company or its 50% or less owned companies were as follows: • OSV Partners had two interest rate swap agreements with maturities in 2020 that call for OSV Partners to pay a fixed rate of interest ranging from 1.89% to 2.27% plus margin on the aggregate amortized notional value of $22.8 million and receive a variable interest rate based on LIBOR on the aggregate amortized notional value. • MexMar had five interest rate swap agreements with maturities in 2023 that call for MexMar to pay a fixed rate of interest ranging from 1.71% to 2.10% plus margin on the aggregate amortized notional value of $83.2 million and receive a variable interest rate based on LIBOR on the aggregate amortized notional value. Prior to 2017, the Company held positions in publicly traded equity options that convey the right or obligation to engage in a future transaction on the underlying equity security or index. The Company’s investment in equity options primarily included positions in energy related businesses. These contracts were typically entered into to mitigate the risk of changes in market value of marketable security positions that the Company was either about to acquire, had acquired or was about to dispose. 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 U.S. The Company generally does not enter into contracts with forward settlement dates beyond twelve to eighteen months. There are no outstanding contracts at December 31, 2019.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	11. 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 levels of inputs that may be used to measure fair value. Level 1 Level 2 Level 1 Level 3 The Company’s financial assets and liabilities as of December 31 that are measured at fair value on a recurring basis were as follows (in thousands): Level 1 Level 2 Level 3 (1) 2019 ASSETS Construction reserve funds $ 12,893 $ — $ — LIABILITIES Derivative instruments (included in other current liabilities) — 3,009 — Conversion Option Liability on Convertible Senior Notes — — 5,205 2018 ASSETS Derivative instruments (included in other receivables) $ — $ 419 $ — Construction reserve funds 28,221 — — LIABILITIES Derivative instruments (included in other current liabilities) — 1,659 — Conversion Option Liability on Convertible Senior Notes — — 5,276 (1) For the year ended December 31, 2019, the Company recognized a $0.1 million gain in the fair market valuation of the Convertible Senior Notes, as valued by an independent third-party. Level 3 Measurement. The fair value of the conversion option liability on the Convertible Senior Notes is estimated with significant inputs that are both observable and unobservable in the market and therefore is considered a Level 3 fair value measurement. The Company used a binomial lattice model that assumes the holders will maximize their value by finding the optimal decision between redeeming at the redemption price or converting into shares of Common Stock. This model estimates the fair value of the conversion option as the differential in the fair value of the notes including the conversion option compared with the fair value of the notes excluding the conversion option. The significant observable inputs used in the fair value measurement include the price of Common Stock and the risk-free interest rate. The significant unobservable inputs are the estimated Company credit spread and Common Stock volatility, which were based on comparable companies in the marine transportation and energy industries. The estimated fair value of the Company’s other financial assets and liabilities as of December 31 were as follows (in thousands): Estimated Fair Value Carrying Amount Level 1 Level 2 Level 3 2019 ASSETS Cash, cash equivalents and restricted cash $ 87,047 $ 87,047 $ — $ — Investments, at cost, in 50% or less owned companies (included in other assets) 132 see below LIABILITIES Long-term debt, including current portion 398,053 — 380,815 — 2018 ASSETS Cash, cash equivalents and restricted cash $ 93,254 $ 93,254 $ — $ — Investments, at cost, in 50% or less owned companies (included in other assets) 132 see below LIABILITIES Long-term debt, including current portion 404,666 — 388,949 — 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 practicable to estimate the fair value of the Company’s investments, at cost, in 50% or less owned companies because of the lack of a quoted market price and the inability to estimate fair value without incurring excessive costs. Considerable judgment was required in developing certain of the estimates of fair value and, accordingly, the estimates presented herein are not necessarily indicative of the amounts that the Company could realize in a current market exchange. The Company’s non-financial assets and liabilities that were measured at fair value during the years ended December 31 were as follows (in thousands): Level 1 Level 2 Level 3 2019 ASSETS Property and equipment: AHTS $ — $ 520 $ — FSV — 1,858 — 2018 ASSETS Property and equipment: AHTS $ — $ 2,000 $ — Liftboats — — 134,775 Specialty — 4,500 — Property and equipment. During the years ended December 31, 2019, 2018 and 2017 the Company recognized impairment charges of $12.0 million, $14.6 million, and $27.5 million, respectively, associated with certain offshore support vessels. The Level 2 fair values were determined based on the contracted sales prices of the property and equipment, sales prices of similar property and equipment or scrap value, as applicable. The Level 3 fair values were determined based on third-party valuations using significant inputs that are unobservable in the market. Due to limited market transactions, the primary valuation methodology applied by the appraisers was an estimated cost approach less estimated economic depreciation for comparably aged and conditioned assets less estimated economic obsolescence based on market data or utilization and rates per day worked trending of the vessels since 2014. The significant unobservable inputs used in the fair value measurement for the AHTS fleet during 2018 listed above were contributed by MOI to wholly-owned subsidiaries of FGH and recorded at fair value. The Level Level Investments, at equity, in 50% or less owned companies. During the year ended December 31, 2019, the Company marked its investments to zero in certain of its 50% of less owned companies. December 31, 2017, the Company marked its investments to fair value in certain of its 50% or less owned companies. The Level 2 fair values were determined based on the purchase price of acquired interests or sales prices of similar equipment held in the venture. The Level 3 fair values were determined based on third-party valuations using significant inputs that are unobservable in the market. The Company’s partner declined to participate in a capital call from Falcon Global during 2017 and, as a consequence, the Company obtained 100% voting control of Falcon Global in accordance with the terms of the operating agreement (see Note 5). Upon the change in control, the Company’s investment in Falcon Global was deemed to approximate fair value.

Warrants

Warrants	12 Months Ended
	Dec. 31, 2019
Warrants And Rights Note Disclosure [Abstract]
Warrants	12. WARRANTS On April 26, 2018, the Company closed a private placement of its Common Stock and Warrants to purchase its Common Stock (which were issued to certain investors in place of Common Stock to facilitate compliance with Jones Act restrictions) for aggregate gross proceeds of $56,855,000 (the “PIPE Private Placement”) with certain qualified institutional buyers and other accredited investors. The PIPE Private Placement included the issuance of 2,168,586 shares of Common Stock (the “PIPE Shares”) and Warrants to purchase 674,164 shares of the Common Stock at an exercise price of $0.01 per share (the “PIPE Warrants”). The PIPE Warrants were issued to CME on April 26, 2018, have a 25-year term and an exercise price of $0.01 per share. On May 2, 2018 the Company and Carlyle entered into an amendment and exchange agreement pursuant to which Carlyle exchanged $50.0 million in principal amount of the Convertible Senior Notes for warrants in order to purchase 1,886,292 shares of common stock at an exercise price of $0.01 per shares (the “Exchange Warrants” and, together with the PIPE Warrants, the “Warrants”). The Exchange Warrants have a 25-year term, which commenced May 2, 2018. On May 31, 2018 and June 8, 2018, the 250,693 and 38,857 Warrants were exercised, respectively for a penny per share which left 2,271,406 Warrants outstanding as of December 31, 2018. On May 28, 2019 and June 14, 2019, 380,000 and 64,440 Warrants were exercised, respectively for a penny per share which left 1,826,966 Warrants outstanding as of December 31, 2019. In connection with the exercise of Warrants on June 14, 2019, 49 shares of Common Stock were withheld as payment for the exercise price of the exercised Warrants.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	13. On January 1, 2019, the Company adopted ASC 842 regarding the recording of lease on the balance sheet. This adoption resulted in an increase of $10.4 million, net of tax, to the Company’s opening retained earnings for the current period. On January 9, 2019, certain indirect wholly owned subsidiaries of SEACOR Marine acquired three FSVs in exchange for the private placement of 603,872 shares of its Common Stock to domestic U.S. holders affiliated with the McCall family of Louisiana. The value of the vessels and the Common Stock was $7.8 million based on the closing price of a share of Common Stock on the NYSE on the day of the exchange. The Common Stock was issued in reliance upon the exemption from registration provided by Section 4(a)(2) of the Securities Act. The Company has operated the acquired vessels for the past ten years under a revenue sharing pooling agreement that included four of its owned FSVs of similar specification. In accordance with its terms, this pooling agreement was terminated. On January 25, 2019, Seabulk Overseas Transport, Inc., a wholly owned subsidiary of SEACOR Marine (“Seabulk Overseas”), acquired a 6.25% minority interest in Windcat Workboats that it did not previously own upon the exercise of certain put options by one of the two minority owners pursuant to the terms of a subscription and shareholders agreement, as amended (the “Subscription and Shareholders Agreement”), in exchange for consideration of £1.6 million (approximately $2.0 million) in cash. The Company acquired the other 6.25% minority interest in Windcat Workboats that the Company did not already own on March 15, 2019 in exchange for consideration of 50,000 shares of Common Stock and €1.2 million (approximately $1.4 million) in cash. The Common Stock was issued in a private placement in reliance upon the exemption from registration provided by Section 4(a)(2) of the Securities Act. The two acquisitions resulted in Seabulk Overseas owning (and SEACOR Marine indirectly owning) 100% of Windcat Workboats. On January 1, 2018, the Company adopted a new accounting standard issued by the FASB on October 24, 2016, which requires companies to account for the income tax effects of intercompany sales and transfers of assets other than inventory. The impact of the adoption of the new standard resulted in a reduction of $12.1 million to the Company’s opening retained earnings. On February 8, 2018, the Company formed FGH, a joint venture between the Company and MOI. In accordance with the terms of the Joint Venture Contribution and Formation Agreement, the Company and MOI contributed certain liftboat vessels and other related assets to the joint venture and assumed certain operating liabilities and indebtedness associated with the liftboat vessels and related assets. The transaction consolidated 15 liftboat vessels operated by the Company and six liftboat vessels previously operated by MOI. FGUSA, a wholly-owned subsidiary of FGH, paid $15.0 million of MOI’s debtor-in-possession obligations and entered into a $131.1 million credit agreement comprised of the FGUSA Term Loan and the FGUSA Revolving Loan Facility. The Company performed a fair market valuation of the debt resulting in a debt discount of $9.5 million on the FGUSA Term Loan and $0.5 million debt discount on the FGUSA Revolving Loan Facility, which will be amortized over the life of the FGUSA Credit Facility. The debt discount on the FGUSA Revolving Loan Facility resulted in an adjustment of $0.4 million to stockholder’s equity. On March 26, 2018, the Company issued 103,213 shares of Common Stock to an accredited investor for a total of $1.8 million in gross proceeds pursuant to a private placement in reliance on the exemption from registration set forth in Section 4(a)(2) of the Securities Act. On April 26, 2018, the Company closed the PIPE Private Placement resulting in aggregate gross proceeds of $56.9 million. The PIPE Private Placement included the issuance of the PIPE Shares and the PIPE Warrants. The PIPE Shares and PIPE Warrants were issued in reliance upon the exemption from registration provided by Section 4(a)(2) of the Securities Act. On May 2, 2018, the Company and Carlyle entered into the Exchange pursuant to which Carlyle exchanged $50.0 million in principal amount of the Convertible Senior Notes for the Carlyle Warrants. The Carlyle Warrants were issued in reliance upon the exemption from registration provided by Section 4(a)(2) of the Securities Act. On May 31, 2018 and June 8, 2018, there were 250,693 and 38,857 warrants exercised, respectively for a penny per share. There were 108 shares of Common Stock held in treasury in exchange for the payment of the penny per warrant on certain of the warrants converted.

Noncontrolling Interests in Sub

Noncontrolling Interests in Subsidiaries	12 Months Ended
	Dec. 31, 2019
Noncontrolling Interest [Abstract]
Noncontrolling Interests in Subsidiaries	14. Noncontrolling interests in the Company’s consolidated subsidiaries as of December 31 were as follows (in thousands): Noncontrolling Interests 2019 2018 Falcon Global Holdings 28.0 % $ 21,119 $ 26,989 Windcat Workboats — (1) — 2,115 Other 1.8 % 313 300 $ 21,432 $ 29,404 (1) As of December 31, 2018, noncontrolling interest was 12.5% Falcon Global Holdings. On February 8, 2018, a wholly-owned subsidiary of SEACOR Marine and MOI formed and capitalized a joint venture named Falcon Global Holdings LLC to operate the Company’s liftboat fleet. In connection therewith and MOI’s plan of reorganization, which was confirmed on January 18, 2018, MOI emerged from its Chapter 11 bankruptcy case. In accordance with the terms of a Joint Venture Contribution and Formation Agreement, the Company and MOI contributed certain liftboat vessels and other related assets to FGH and its designated subsidiaries and FGH and its designated subsidiaries assumed certain operating liabilities and indebtedness associated with the liftboat vessels and related assets. The transaction consolidates the 15 liftboat vessels operated by the Company and six liftboat vessels previously operated by MOI. The total capital contributed to FGH was approximately $112.5 million of which, $43.3 million was transferred from FGI and $18.8 million was contributed by MOI and recorded at fair value, with the remaining capital contributed by the Company. The Company consolidates FGH as the Company holds 72% of the equity interest in FGH and is entitled to appoint a majority of the board of managers of FGH. During the year ended December 31, 2019, the net loss of FGH was $21.0 million, of which $5.9 million was attributable to noncontrolling interest. As of December 31, 2019, the net assets of FGH were $77.2 million. Windcat Workboats. Prior to January 25, 2019, Seabulk Overseas, a wholly-owned subsidiary of the Company, owned 87% of Windcat Workboats. On January 25, 2019, Seabulk Overseas acquired 6.25% minority interest in Windcat Workboats that it did not previously own. Seabulk Overseas acquired the remaining 6.25% interest in Windcat Workboats that the Company did not already own on March 15, 2019. As of December 31, 2018, the net assets of Windcat Workboats was $16.9 million. During the year ended December 31, 2018, the net loss of Windcat Workboats was $3.1 million, of which $0.4 million was attributable to noncontrolling interests.

Savings and Multi-employer Pens

Savings and Multi-employer Pension Plans	12 Months Ended
	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Savings and Multi-employer Pension Plans	15. SEACOR Marine Savings Plan. On January 1, 2016, the Company’s eligible U.S. based employees were transferred from the SEACOR Holdings sponsored defined contribution plan to the “SEACOR Marine 401(k) Plan,” a new Company sponsored defined contribution plan (the “Savings Plan”). Effective upon the June 1, 2017 Spin-off, the Company discontinued its contribution to the Savings Plan up until January 1, 2019, at which time the Company’s contribution will be limited to 1.0% of an employee’s wages. The Savings Plan costs for the year ended December 31, 2019 was $0.3 million. MNOPF and MNRPF. Certain of the Company’s subsidiaries are participating employers in two industry-wide, multi-employer, defined benefit pension funds in the United Kingdom: the U.K Merchant Navy Officers Pension Fund (“MNOPF”) and the U.K. Merchant Navy Ratings Pension Fund (“MNRPF”). The Company’s participation in the MNOPF began with the acquisition of the Stirling group of companies (the “Stirling Group”) in 2001 and relates to certain officers employed between 1978 and 2002 by the Stirling Group and/or its predecessors. The Company’s participation in the MNRPF also began with the acquisition of the Stirling Group in 2001 and relates to ratings employed by the Stirling Group and/or its predecessors through today. Both of these plans are in deficit positions and, depending upon the results of future actuarial valuations, it is possible that the plans could experience funding deficits that will require the Company to recognize payroll related operating expenses in the periods invoices are received. 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, the Company was invoiced and expensed $19.4 million for its allocated share of the then cumulative funding deficits, including portions deemed uncollectible due to the non-existence or liquidation of certain former employers. The invoiced amounts have been re-paid in full, other than with respect to $2.6 million invoiced in 2013, for which the Company has a repayment plan with the trustees of the MNOPF to repay such invoice in full by December 31, 2023. As of December 31, 2019, the remaining current and long-term liability due to the MNOPF were $0.3 million and $0.7 million, respectively. On November 7, 2018, the Company received notice from MNOPF that a deficit of £9.0 million existed but noted that the trustee did not propose to collect any additional funds in respect of such deficit. Depending on the results of future valuations, it is possible that the MNOPF will experience further funding deficits requiring the Company to recognize payroll related expenses in the periods the notice is received. 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, the Company was invoiced and expensed $6.9 million for its share of a funding deficit in the MNRPF. The Company had a repayment plan with the trustees of the MNRPF for the amount to be repaid in full by October 30, 2018 and the amounts were settled by that date. On July 20, 2018, the Company was notified of additional contributions due and recognized in the second quarter of 2018 payroll related expenses of $1.19 million (£0.9 million) for its allocated share of the cumulative funding deficit including portions deemed uncollectible due to the non-existence or liquidation of certain former employers. These additional contributions were invoiced in September 2018 and are payable in four annual installments beginning October 2018. As of December 31, 2019, all invoices related to the MNRPF have been settled in full. Depending upon the results of future actuarial valuations it is possible that the plan could experience further funding deficits that will require the Company to recognize payroll related operating expenses for those periods. Other Plans. Certain employees participate in other defined contribution plans in various international regions including the United Kingdom and Singapore. During the years ended December 31, 2019, 2018 and 2017, the Company incurred costs of $0.3 million in 2019 and $0.2 million for 2018 and 2017, primarily from employer matching contributions.

Share Based Compensation

Share Based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share Based Compensation	16. Equity Incentive Plan. During 2017, the Company adopted the SEACOR Marine Holdings Inc. 2017 Equity Incentive Plan (the “2017 Plan”). The 2017 Plan authorizes the Compensation Committee, or another committee designated by the Board and made up of two or more non-employee directors and outside directors, to provide equity-based or other incentive-based compensation for the purpose of attracting and retaining the Company and its affiliates’ directors, employees and certain consultants, and providing those directors, employees and consultants incentive opportunities and rewards for superior performance. The Board has authorized the issuance of 2,174,000 shares of Common Stock in connection with awards pursuant to the 2017 Plan, which was equal to 10% of the total number shares of SEACOR Marine Common Stock outstanding at the time of authorization. The types of awards under the 2017 Plan may include stock options, stock appreciation rights, restricted stock and restricted stock units, performance awards and other stock-based awards. As of December 31, 2019, a total of 567,424 shares remained available for issuance under the 2017 Plan. Restricted stock typically vests from one to four years after the date of grant and options to purchase shares of Common Stock typically vest and become exercisable from one to four years after date of grant. Options to purchase shares of Common Stock granted under the 2017 Plan expire no later than the tenth anniversary of the date of grant. In the event of a participant’s death, retirement, termination by the Company without cause or a change in control of the Company, as defined in the 2017 Plan, restricted stock vests immediately and in the event of participant’s death or retirement, options to purchase shares of Common Stock vest and become immediately exercisable. Distribution of SEACOR Marine Restricted Stock by SEACOR Holdings. Certain officers and employees of the Company previously received compensation through participation in SEACOR Holdings share award plans. Pursuant to the Employee Matters Agreement with SEACOR Holdings, participating Company personnel vested in all outstanding SEACOR Holdings share awards upon the Spin-off in 2017 and received SEACOR Marine restricted stock from the Spin-off distribution in connection with outstanding SEACOR Holdings restricted stock held. Therefore, the Company paid SEACOR Holdings $2.7 million upon completion of the Spin-off for the distribution of 120,693 shares of SEACOR Marine restricted stock, which is being amortized over the participants’ remaining original vesting periods. Employee Stock Purchase Plan. During 2017, the Company adopted the SEACOR Marine Holdings Inc. 2017 Employee Stock Purchase Plan (the “Marine ESPP”). The Marine ESPP, if implemented by the Company’s board of directors, will permit the Company to offer shares of its Common Stock for purchase by eligible employees at a price equal to 85% of the lesser of (i) the fair market value of a share of its Common Stock on the first day of the offering period or (ii) the fair market value of a share of its Common Stock on the last day of the offering period. There are 300,000 shares of the Company’s Common Stock reserved for issuance under the Marine ESPP during the ten years following its adoption. Share Award Transactions. The following transactions have occurred in connection with the Company’s share-based compensation under the 2017 Plan during the years ended December 31: 2019 2018 Director Stock Awards Granted 30,197 19,285 Restricted Stock Activity: Outstanding as of the beginning of year 192,346 121,693 Granted - 2017 Plan 245,400 (1) 120,600 Vested 131,937 49,947 Forfeited 2,200 — Outstanding as of the end of year 303,609 192,346 Stock Option Activity: Outstanding as of the beginning of year 805,566 613,700 Granted - 2017 Plan 230,503 258,491 Exercised 113,750 66,625 Forfeited 8,750 — Outstanding as of the end of year 913,569 805,566 (1) Excludes 91,600 grants of performance-based stock units that are not considered outstanding until such time that they become probable to vest. During the year ended December 31, 2019, the Company recognized $5.3 million of compensation expense related to stock awards, restricted stock and stock options granted to employees and directors under the 2017 Plan. As of December 31, 2019, the Company had approximately $6.5 million in total unrecognized compensation costs. The weighted average period over which the compensation cost of non-vested awards will be recognized is approximately 1.25 and 1.33 years for stock options and restricted stock, respectively. During the year ended December 31, 2018, the Company recognized $4.4 million of compensation expense related to stock awards, restricted stock and stock options granted to employees and directors under the 2017 Plan. As of December 31, 2018, the Company had approximately $6.8 million in total unrecognized compensation costs. During the year ended December 31, 2017, the Company recognized $0.8 million of compensation expense related to stock awards, restricted stock and stock options granted to employees and directors under the 2017 Plan and $0.6 million of compensation expense related to SEACOR Marine restricted stock distributed to employees by SEACOR Holdings in connection with the Spin-off (collectively referred to as “share awards”). As of December 31, 2017, the Company had approximately $5.2 million in total unrecognized compensation costs. The weighted average fair value of restricted stock granted under the 2017 Plan was $13.28 and $21.63 for the year ended December 31, 2019 and 2018, respectively. The fair value was based the closing price of the Company’s stock on the day of the grant. The weighted average fair value of stock options granted under the 2017 Plan was $8.73 and $9.99 for the year ended December 31, 2019 and 2018, respectively. The fair value of each option granted during the years ended December 31, 2019 and 2018, was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions: (a) no dividend yield; (b) weighted average expected volatility of 51.1 and 50.4, respectively; (c) weighted average discount rate of 2.1% and 2.79%, respectively and (d) expected life of 9.75 and 6.00 years, respectively. The intrinsic value of stock options exercised during 2019 was $1.6 million. During the year ended December 31, 2019, the number of shares and the weighted average grant price of restricted stock transactions were as follows: Restricted Stock Number of Shares Weight Average Grant Price Non-Vested as of December 31, 2018 192,346 $ 22.32 Granted 245,400 13.28 Vested 131,937 13.45 Forfeited 2,200 17.26 Non-Vested as of December 31, 2019 303,609 20.46 During the year ended December 31, 2019, the number of shares and the weighted average exercise price on stock option transactions were as follows: Stock Options Number of Shares Weight Average Grant Price Non-Vested as of December 31, 2018 805,566 $ 14.81 Granted 230,503 8.73 Exercised 113,750 13.98 Forfeited 8,750 20.93 Non-Vested as of December 31, 2019 913,569 14.85 Exercisable as of December 31, 2019 (1) 408,075 14.69 (1) The weighted average remaining contractual term is 8.23 years. As of December 31, 2019, there were 913,569 stock options outstanding with a weighted average exercise price of $14.85 and a weighted average remaining contractual term of 8.47 years. As of December 31, 2019, there was no aggregate intrinsic value for options outstanding.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	17. Transactions with SEACOR Holdings. The Company provided services of $0.1 million to SEACOR Holdings during the year ended December 31, 2017. 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 Transition Services Agreements, an Employee Matters Agreement and a Tax Matters Agreement. As of December 31, 2019, SEACOR Holdings had guaranteed $22.8 million for various obligations of the Company, including performance obligations under sale-leaseback arrangements (see Note 7) and invoiced amounts for funding deficits under the MNOPF (see Note 15). As of December 31, 2018, SEACOR Holdings had guaranteed $40.6 million for various obligations of the Company, including: BNDES Equipment Construction Finance Notes (see Note 8); letters of credit issued on behalf of the Company; performance obligations under sale-leaseback arrangements (see Note 7); and invoiced amounts for funding deficits under the MNOPF (see Note 15). Pursuant to the Transition Services Agreement with SEACOR Holdings, SEACOR Holdings charges the Company a fee of 0.5% on outstanding guaranteed amounts, which declines as the guaranteed obligations are settled by the Company. The Company recognized guarantee fees in connection with sale-leaseback arrangements of $0.2 million, $0.3 million and $0.3 million during 2019, 2018 and 2017, respectively, as additional leased-in equipment operating expenses in the accompanying consolidated statements of loss. Guarantee fees paid to SEACOR Holdings for all other obligations are recognized as SEACOR Holdings guarantee fees in the accompanying consolidated statements of loss. Pursuant to one of the Transitions Services Agreements with SEACOR Holdings, the Company is obligated to reimburse SEACOR Holdings up to 50% of the severance and restructuring costs actually incurred by SEACOR Holdings as a result of the Spin-off up to, but not in excess of, $6.0 million (such that the Company shall not be obligated to pay more than $3.0 million). As of Following the completion of the Spin-off, the Company is no longer charged for management fees or shared services allocation (see below) for administrative support by SEACOR Holdings; however, the Company continues to be supported by SEACOR Holdings for corporate services pursuant to the Transition Services Agreements with SEACOR Holdings under which it was initially charged $6.3 million annually for these services. The fees incurred have declined as the services and functions provided by SEACOR Holdings are terminated and replicated within the Company. For the year ended December 31, 2019, 2018, and 2017, the Company incurred fees of $0.6 million, $4.5 million and $3.3 million, respectively, for these services that were recognized as additional administrative and general expenses in the accompanying consolidated statements of loss. 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 year ended December 31, 2017 (in thousands): 2017 Participation in SEACOR Holdings employee benefit plans $ 899 Participation in SEACOR Holdings share award plans 8,383 Shared services allocation for administrative support 1,932 $ 11,214 • 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 longer participates in SEACOR Holdings’ self-insured health benefit plans; • 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 million upon completion of the Spin-off, including $2.7 million for the distribution of 120,693 shares of SEACOR Marine restricted stock (see Note 16), which is being amortized over the participants’ remaining original vesting periods, and $6.7 million on the accelerated vesting of SEACOR Holdings share awards, which was immediately recognized. In addition, the Company recognized and paid share award expense of $1.7 million through the date of the Spin-off; and • prior to the Spin-off, SEACOR Holdings provided certain administrative support services to the Company under a shared services arrangement, including but not limited to payroll processing, information systems support, benefit plan management, cash disbursement support and treasury management. The Company was charged for its share of actual costs incurred generally based on volume processed or units supported. Transactions regarding OSV Partners. Charles Fabrikant (Non-Executive Chairman of SEACOR Marine), John Gellert (President, Chief Executive Officer and Director of SEACOR Marine), Jesús Llorca (Executive Vice President and Chief Financial Officer 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 unaffiliated limited partners of OSV Partners who wished to dispose of their interests. During 2018, OSV Partners (i) raised $7.5 million of cash: $5 million in the form of second lien debt and $2.5 million in the form of class A preferred interests and (ii) obtained commitments from the limited partners of OSV Partners for an additional $2.5 million in the form of class a preferred interest. On December 18, 2019, the general partner of OSV Partners called these remaining commitments. As of December 31, 2019, limited liability companies controlled by management and directors of the Company had invested $1.5 million, or 3.9%, in the limited partner interests; $0.3 million, or 5.0%, in preferred interests; $0.2 million, or 3.9%, in the form of second lien debt; and $0.2 million, or 3.9%, in the class A preferred interests of OSV Partners. As of December 31, 2019, the investments of Messrs. Fabrikant, Gellert and Llorca in such limited liability companies were $0.3 million, $0.4 million and $0.2 million, respectively, representing 39.6% of such limited liability companies’ membership interests. The general partner of OSV Partners is a joint venture managed by the Company and an unaffiliated third-party. The Company owns 30.4% in the limited partner interests, 38.6% in the preferred interests, 43.0% of the second lien debt, and 43.0% in the class A preferred interest of OSV Partners. The Company agreed to abate to zero the management fees it charges to OSV Partners through December 31, 2020. Transactions regarding Windcat Workboats. On January 25, 2019, Seabulk Overseas, a wholly-owned subsidiary of SEACOR Marine, acquired a 6.25% minority interest in Windcat Workboats that it did not previously own upon the exercise of a put option by one of the two minority owners, each of whom is a member (or an affiliate of a member) of management of Windcat Workboats, pursuant to the terms of a certain Subscription and Shareholders Agreement, as amended, for consideration of £1.6 ($2.0 million). On March 15, 2019, Seabulk Overseas acquired the other 6.25% minority interest in Windcat Workboats that it did not previously own for consideration of 50,000 shares of Common Stock and €1.2 million (approximately $1.4 million) in cash. The two acquisitions resulted in Seabulk Overseas owning 100% of Windcat Workboats, a consolidated subsidiary which owns and operates the Company’s CTV that are primarily used to move personnel and supplies in Europe’s offshore wind markets Transactions with Carlyle. On December 1, 2015, the Company issued $175.0 million aggregate principal amount of its Convertible Notes to investment funds managed and controlled by Carlyle. Interest on the Convertible Notes is payable semi-annually on June 15 and December 15 of each year, commencing June 15, 2016 (see Note 8). Pursuant to the note purchase agreement for the Convertible Notes and the Investment Agreement, the Company must use reasonable best efforts, subject to its directors’ fiduciary duties, to cause a person designated by Carlyle to be appointed as a director on the Board, if Carlyle, solely as a result of the conversion of the Convertible Notes, collectively owns, continues to own, or would (upon conversion) own 10.0% or more of the Company’s outstanding shares of Common Stock. During 2017, Ferris Hussein served on the Board as the director designated by Carlyle until his resignation on April 17, 2018. Carlyle has not exercised this right subsequent to Mr. Hussein’s resignation but retains the right to appoint a Board member. Mr. Hussein has been designated by Carlyle to observe meetings of the Board pursuant to Carlyle’s observer rights under the Convertible Notes. This observation right will terminate at the time Carlyle owns less than $50.0 million in aggregate principal amount of the Convertible Notes or a combination of the Convertible Notes and our Common Stock representing less than 5.0% of the Company’s Common Stock outstanding on a fully diluted basis, assuming the conversion of all of the Convertible Notes and Warrants to purchase Common Stock held by Carlyle. In April 2018, the Company entered into the following Exchange and other transactions with Carlyle pursuant to which: • the Company exchanged $50.0 million in principal amount of the Convertible Notes for Common Stock (or warrants to purchase an equivalent number of shares of Common Stock at an exercise price of $0.01 per share) at an exchange rate of 37.73 per $1,000 principal amount of the Notes (equivalent to an exchange price of $26.50) for a total of approximately 1.9 million shares of Common Stock including Common Stock issuable upon exercise of the Exchange Warrants (the “Exchange”); • the Company and Carlyle amended the $125.0 million in principal amount of Convertible Notes that remains outstanding after the Exchange to (i) increase the interest rate from 3.75% per annum to 4.25% per annum and (ii) extend the maturity of the Convertible Notes by 12 months to December 1, 2023; and • Carlyle purchased 750,000 shares of Common Stock in a private placement whereby the Company issued an aggregate of 2,168,586 shares of Common Stock and warrants to purchase 674,164 shares of Common Stock at an exercise price of $0.01 per share in a private placement exempt from registration under the Securities Act (the “PIPE Issuance”) for aggregate consideration of $15.0 million. Transactions with CME . Mr. Alfredo Miguel Bejos, who was elected as a director at the Company’s 2019 annual meeting, currently serves as President and Chief Executive Officer of CME. The Company entered into the following transactions with CME in 2018: • On April 26, 2018, CME purchased 325,836 shares of Common Stock and 674,164 warrants to purchase the Company’s Common Stock in the PIPE Issuance for aggregate consideration of $20.0 million. • On December 20, 2018, MEXMAR Offshore, a joint venture that is 49.0% owned by a subsidiary of the Company and 51.0% owned by a subsidiary of CME, acquired UP Offshore. UP Offshore was acquired for nominal consideration. In connection with the acquisition, UP Offshore’s existing debt was refinanced with $95.0 million of new indebtedness composed of (i) a $70.0 million six-year debt facility provided by UP Offshore’s existing lenders that is non-recourse to the Company, CME or any of their respective subsidiaries, (ii) a $15.0 million loan from MexMar, a joint venture between CME and the Company, to fund capital expenditures on two vessels and (iii) a $10.0 million loan from MEXMAR Offshore to fund working capital requirements funded by an approximate $5.0 million capital contribution to MEXMAR Offshore by each of the Company and CME. The Company also participates in a variety of other joint ventures with CME, including MexMar, SMLLC and OVH. During 2018, the Company earned charter revenue of $16.5 million and management fees of $300,000 from MexMar. These agreements with MexMar were negotiated at arms-length in the ordinary course of business. In addition, in 2018: • The Company created a new subsidiary, SMLLC and contributed the Seacor Marlin supply vessel into SMLLC. On September 13, 2018, the Company sold 51.0% of SMLLC to MEXMAR Offshore, a wholly-owned subsidiary of MexMar, for $8.0 million in cash. The Seacor Marlin supply vessel was pledged as collateral under the MexMar credit facility, for which the Company receives an annual collateral fee. • The Company received a return of a capital advance from MexMar of $9.8 million. In 2019, the Company sold an FSV to OVH for $2.4 million through a seller’s finance agreement. Other Transactions JMG GST LLC, an entity managed by Mr. John Gellert, President, Chief Executive Officer and director of SEACOR Marine, purchased $1,000,000, or 50,000 shares, of Common Stock in the PIPE Issuance.

Commitment and Contingencies

Commitment and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	18. COMMITMENTS AND CONTINGENCIES As of December 31, 2019, the Company had capital commitments of $35.9 million for four PSVs, one CTV and other equipment, to be delivered in 2020. The Company has indefinitely deferred an additional $30.2 million of orders with respect to three FSVs. In 2015, the Brazilian Federal Revenue Office issued a tax-deficiency notice to Seabulk Offshore do Brasil Ltda (“Seabulk Offshore do Brasil”), an indirectly wholly owned subsidiary of SEACOR Marine, with respect to certain profit participation contribution (“PIS”) and social security financing contribution (“COFINS”) requirements alleged to be due from Seabulk Offshore do Brasil (“Deficiency Notice”). In February 2015, Company deposited with the relevant Brazilian court an amount equal to USD $1.2 million and appealed the Deficiency Notice on the basis that such contributions were not applicable in the circumstances of a 70%/30% cost allocation structure. The case was remitted to the second instance and is currently awaiting trial. Recently, a local Brazilian law was enacted that supports the Company’s position that such contribution requirements are not applicable, but it is uncertain whether such law will be taken into consideration with respect to administrative proceedings commenced prior to the enactment of the law. Accordingly, the success of Seabulk Offshore do Brasil in the administrative proceedings cannot be assured. The potential range of levies arising from the Deficiency Notice is R$12.8 million - R$17.5 million (USD $3.2 million – USD $4.3 million based on the exchange rate as of December 31, 2019). In the normal course of its business, the Company becomes involved in various other litigation matters including, among other things, claims by third-parties for alleged property damages and personal injuries. Management has used estimates in determining the Company’s potential exposure to these matters and has recorded reserves in its financial statements related thereto where appropriate. It is possible that a change in the Company’s estimates of that exposure could occur, but the Company does not expect such changes in estimated costs could have a material adverse effect on the Company’s business, financial position, results of operations, cash flows and growth prospects. The Company has $2.0 million available under its Windcat Workboats credit facilities.

Major Customers and Segment Inf

Major Customers and Segment Information	12 Months Ended
	Dec. 31, 2019
Notes To Financial Statements [Abstract]
Major Customers and Segment Information	19. During the year ended December 31, 2019, Seacor Marine Arabia LLC was responsible for $30.8 million or 15% ($20.3 million or 10% from Zamil Offshore and $10.5 million or 5% from Saudi Aramco) of the Company’s total consolidated operating revenues from continuing operations. During the year ended December 31, 2018, Seacor Marine Arabia LLC was responsible for $21.4 million or 10% ($12.2 million or 6% from Zamil Offshore and $9.2 million or 4% from Saudi Aramco) of the Company’s total consolidated operating revenues from continuing operations. During the year ended December 31, 2017, Seacor Marine Arabia LLC was responsible for $16.0 million or 13% ($4.5 million or 4% from Zamil Offshore and $11.2 million or 9% from Saudi Aramco) of the Company’s total consolidated operating revenues from continuing operations. During the years ended December 31, 2019, 2018 and 2017, the ten largest customers of the Company accounted for approximately 44%, 49%, and 58%, respectively, of the Company’s operating revenues from continuing operations. The loss of one or more of these customers could have a material adverse effect on the Company’s results of operations and cash flows. For the years ended December 31, 2019, 2018 and 2017, approximately 78%, 36%, and 82%, respectively, of the Company’s operating revenues and $(12.8) million, $(3.0) million, and $2.0 million, respectively, of equity in (losses) earnings from 50% or less owned companies, net of tax, were derived from its continuing foreign operations. 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 be redeployed among the geographic regions, subject to flag restrictions, as changes in market conditions dictate. Because of this asset mobility, operating revenues and long-lived assets in any one country and capital expenditures for long-lived assets and gains or losses on asset dispositions and impairments in any one geographic region are not considered meaningful. 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 Latin America Europe Continuing Operations Total For the year ended December 31, 2019 Operating Revenues: Time charter $ 38,955 $ 44,160 $ 54,312 $ 11,460 $ 33,414 $ 182,301 Bareboat charter 1,562 — — 3,569 — 5,131 Other 3,806 1,461 1,669 1,390 5,734 14,060 44,323 45,621 55,981 16,419 39,148 201,492 Direct Costs and Expenses: Operating: Personnel 17,491 13,833 16,698 4,459 13,031 65,512 Repairs and maintenance 7,583 4,701 7,182 1,348 3,855 24,669 Drydocking 4,594 490 600 161 3 5,848 Insurance and loss reserves 2,370 1,051 1,449 311 857 6,038 Fuel, lubes and supplies 2,936 3,471 2,904 1,056 960 11,327 Other 393 4,354 3,095 1,182 1,307 10,331 35,367 27,900 31,928 8,517 20,013 123,725 Direct Vessel Profit $ 8,956 $ 17,721 $ 24,053 $ 7,902 $ 19,135 77,767 Other Costs and Expenses: Operating: Leased-in equipment $ 10,894 $ 3,090 $ 173 $ 10 $ 1,991 16,158 Administrative and general 44,726 Depreciation and amortization $ 21,947 $ 10,404 $ 16,400 $ 6,205 $ 9,056 64,012 124,896 Losses on Asset Dispositions and Impairments, Net (5,397 ) Operating Loss $ (52,526 ) As of December 31, 2019 Property and Equipment: Historical cost $ 297,392 $ 207,107 $ 292,446 $ 57,534 $ 122,499 $ 976,978 Accumulated depreciation (157,514 ) (57,136 ) (73,039 ) (16,239 ) (55,034 ) (358,962 ) $ 139,878 $ 149,971 $ 219,407 $ 41,295 $ 67,465 $ 618,016 Total Assets (1) $ 224,229 $ 161,915 $ 250,890 $ 116,736 $ 109,874 $ 863,644 (1) Total assets exclude $145,232 thousand of corporate assets. United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Latin America Europe Continuing Operations Total For the year ended December 31, 2018 Operating Revenues: Time charter $ 38,802 $ 43,847 $ 50,072 $ 17,343 $ 22,286 $ 172,350 Bareboat charter — — — 4,635 — 4,635 Other 14,762 7,661 (887 ) 1,554 3,492 26,582 53,564 51,508 49,185 23,532 25,778 203,567 Direct Costs and Expenses: Operating: Personnel 18,708 16,538 16,806 4,399 10,862 67,313 Repairs and maintenance 5,152 6,330 11,172 1,011 3,368 27,033 Drydocking 1,957 2,085 1,362 128 2,261 7,793 Insurance and loss reserves 2,922 1,096 1,371 495 459 6,343 Fuel, lubes and supplies 3,568 3,826 4,027 1,225 863 13,509 Other 393 4,313 3,980 1,130 467 10,283 32,700 34,188 38,718 8,388 18,280 132,274 Direct Vessel Profit $ 20,864 $ 17,320 $ 10,467 $ 15,144 $ 7,498 71,293 Other Costs and Expenses: Operating: Leased-in equipment $ 8,240 $ 4,281 $ 224 $ 5 $ 489 13,239 Administrative and general 46,454 Depreciation and amortization $ 23,227 $ 10,453 $ 18,762 $ 7,908 $ 8,491 68,841 128,534 Losses on Asset Dispositions and Impairments, Net (11,268 ) Operating Loss $ (68,509 ) As of December 31, 2018 Property and Equipment: Historical cost $ 432,336 $ 184,361 $ 306,897 $ 124,177 $ 68,812 $ 1,116,583 Accumulated depreciation (224,737 ) (55,206 ) (81,378 ) (57,002 ) (43,076 ) (461,399 ) $ 207,599 $ 129,155 $ 225,519 $ 67,175 $ 25,736 $ 655,184 Total Assets (1) $ 351,748 $ 140,335 $ 260,002 $ 137,983 $ 18,217 $ 908,285 (1) Total assets exclude $153,151 thousand of corporate assets, and $41,502 thousand of assets held-for-sale United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Latin America Europe Continuing Operations Total For the year ended December 31, 2017 Operating Revenues: Time charter $ 18,079 $ 32,866 $ 33,410 $ 2,977 $ 22,990 $ 110,322 Bareboat charter — — — 4,636 — 4,636 Other 4,217 1,080 474 552 2,140 8,463 22,296 33,946 33,884 8,165 25,130 123,421 Direct Costs and Expenses: Operating: Personnel 15,621 13,419 16,883 809 7,881 54,613 Repairs and maintenance 3,594 5,957 9,037 274 2,462 21,324 Drydocking 1,828 2,180 968 — — 4,976 Insurance and loss reserves 3,286 677 1,444 316 306 6,029 Fuel, lubes and supplies 1,485 2,815 3,727 223 496 8,746 Other 249 3,319 5,240 117 208 9,133 26,063 28,367 37,299 1,739 11,353 104,821 Direct Vessel Profit (Loss) $ (3,767 ) $ 5,579 $ (3,415 ) $ 6,426 $ 13,777 18,600 Other Costs and Expenses: Operating: Leased-in equipment $ 8,709 $ 4,317 $ 1,092 $ 5 $ 326 14,449 Administrative and general 49,865 Depreciation and amortization $ 22,060 $ 9,280 $ 17,724 $ 3,608 $ 7,635 60,307 124,621 Losses on Asset Dispositions and Impairments, Net (23,623 ) Operating Loss $ (129,644 ) As of December 31, 2017 Property and Equipment: Historical cost $ 410,475 $ 192,600 $ 326,378 $ 72,484 $ 56,367 $ 1,058,304 Accumulated depreciation (230,636 ) (57,228 ) (100,435 ) (37,281 ) (34,312 ) (459,892 ) $ 179,839 $ 135,372 $ 225,943 $ 35,203 $ 22,055 $ 598,412 Total Assets (1) $ 310,675 $ 140,173 $ 234,471 $ 103,135 $ 13,650 $ 802,104 (1) Total assets exclude $169,346 thousand of corporate assets, and $37,054 thousand of assets held-for-sale.

Supplemental Information for St

Supplemental Information for Statements of Cash Flows	12 Months Ended
	Dec. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Supplemental Information for Statements of Cash Flows	20. Supplemental information for the years ended December 31 was as follows (in thousands): 2019 2018 2017 Income taxes (paid) refunded, net $ 1,999 $ (316 ) $ 33,773 Interest paid, excluding capitalized interest 22,452 21,031 9,216

Discontinued Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2019
Discontinued Operations And Disposal Groups [Abstract]
Discontinued Operations	21. DISCONTINUED OPERATIONS On December 2, 2019, the Company completed the sale of its North Sea standby safety business, which was previously classified as assets held for sale. Following the completion of the Sale, the Company has no continuing involvement in this business, which is considered a strategic shift in the Company’s operations. Summarized selected operating result of the Company’s assets, previously classified as held for sale were as follows (in thousands): December 31, 2018 Assets from Discontinued Operations: Current assets $ 15,222 Net property and equipment 26,280 41,502 Total current liabilities $ 2,526 For the years ended December 31, 2019 2018 Operating Revenues: Time charter $ 41,214 $ 49,902 Other revenue 45 140 41,259 50,042 Costs and Expenses: Operating 33,836 42,817 Direct Vessel Profit 7,423 7,225 General and Administrative Expenses 4,207 4,524 Lease Expense 60 71 Depreciation 3,504 3,405 (Loss) Gain on Asset Dispositions and Impairments, Net 91 2,521 Operating (Loss) Income (257 ) 1,746 Other Income (Expense) Interest income 11 12 Interest expense (210 ) (465 ) Foreign currency translation loss (75 ) (53 ) (274 ) (506 ) Operating (Loss) Income Before Equity Earnings of 50% or Less Owned Companies, Net of Tax (531 ) 1,240 Income Tax Expense (2 ) 7 Operating (Loss) Income Before Equity Earnings of 50% or Less Owned Companies (529 ) 1,233 Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax 168 137 Net (Loss) Income from Discontinued Operations $ (361 ) $ 1,370

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	22. SUBSEQUENT EVENTS On February 7, 2020, SEACOR Marine Holdings Inc. (“SEACOR Marine”), Falcon Global USA LLC (“FGUSA”), an indirect subsidiary of SEACOR Marine, and certain subsidiaries of FGUSA, entered into a Consent, Agreement and Omnibus Amendments agreement (the “Omnibus Amendment”) to that certain (i) $131.1 million term and revolving loan facility, dated as of February 8, 2018, with a syndicate of lenders administered by JP Morgan Chase Bank, N.A. (the “Credit Facility”) and (ii) obligation guaranty issued by SEACOR Marine, dated February 8, 2018, pursuant to which SEACOR Marine provides a guarantee of certain limited obligations of FGUSA under the Credit Facility (the “Guaranty”). The Omnibus Amendment provides for, among other things, (i) the extension from March 2020 to March 2021 of the commencement of monthly repayment of the term loan, with payments being the lesser of (a) $0.8 million per month and (b) the amount outstanding under the term loan and (ii) the extension of the term of the Guaranty for an As of February 7, 2020, there was $117.3 million of principal outstanding under the Credit Facility, comprised of $102.3 million of principal outstanding under the term loan facility and $15.0 million outstanding under the revolving loan facility.

Quarterly Financial Information

Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	23. 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 necessarily equal the total for the year. Three Months Ended Dec. 31, Sept. 30, June 30, March 31, 2019 Operating Revenues $ 49,070 $ 54,700 $ 52,812 $ 44,910 Operating Loss (10,497 ) (3,355 ) (17,640 ) (21,034 ) Net (Loss) Income: Continuing Operations (19,176 ) (10,341 ) (31,438 ) (28,273 ) Discontinued Operations (2,742 ) (7,899 ) 1,174 — $ (21,918 ) $ (18,240 ) $ (30,264 ) $ (28,273 ) Net Loss attributable to SEACOR Marine Holdings Inc: $ (20,455 ) $ (18,444 ) $ (28,389 ) $ (25,549 ) Basic and Diluted Loss Per Common Share of SEACOR Marine Holdings Inc. Continuing Operations $ (0.74 ) $ (0.49 ) $ (1.31 ) $ (1.16 ) Discontinued Operations $ (0.12 ) $ (0.29 ) $ 0.10 $ 0.05 $ (0.86 ) $ (0.78 ) $ (1.21 ) $ (1.11 ) 2018 Operating Revenues $ 58,897 $ 58,169 $ 47,871 $ 38,630 Operating Loss (11,253 ) (12,207 ) (20,842 ) (24,206 ) Net (Loss) Income: Continuing Operations (7,780 ) (17,706 ) (26,505 ) (31,430 ) Discontinued Operations (189 ) 1,940 (124 ) (258 ) $ (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 and Diluted Loss Per Common Share of SEACOR Marine Holdings Inc. Continuing Operations $ (0.39 ) $ (0.85 ) $ (1.18 ) $ (1.63 ) Discontinued Operations $ 0.04 $ 0.14 $ (0.01 ) $ (0.01 ) $ (0.35 ) $ (0.71 ) $ (1.19 ) $ (1.64 )

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2019
Valuation And Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	SEACOR MARINE HOLDINGS INC. For the Years Ended (in thousands) Description Balance Beginning of Year Charges (Recoveries) to Cost and Expenses Deductions (1) Balance End of Year Year Ended December 31, 2019 Allowance for doubtful accounts (deducted from trade and notes receivable) $ 860 $ (405 ) $ — $ 455 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 (1) Trade receivable amounts deemed uncollectible that were removed from accounts receivable and allowance for doubtful accounts.

Nature of Operations and Acco_2

Nature of Operations and Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Nature of Operations and Segmentation	Nature of Operations and Segmentation. The consolidated financial statements include the accounts of SEACOR Marine and its consolidated subsidiaries (collectively referred to as the “Company”). The Company provides global marine and support transportation services to offshore oil, natural gas and windfarm facilities worldwide. The Company and its joint ventures operate a diverse fleet of offshore support and specialty vessels that (i) deliver cargo and personnel to offshore installations, (ii) handle anchors and mooring equipment required to tether rigs to the seabed, (iii) tow rigs and assist in placing them on location and moving them between regions, (iv) provide construction, well work-over and decommissioning support and (v) carry and launch equipment used underwater in drilling and well installation, maintenance, inspection and repair. Additionally, the Company’s vessels provide accommodations for technicians and specialists, safety support and emergency response services. The Company’s fleet also features crew transfer vessels (“CTVs”) used primarily in windfarm operations. 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. On December 2, 2019, the Company completed the sale of its North Sea standby safety business. Unless the context indicates otherwise, the footnotes to these financial statements reflect continuing operations after the disposition. The Company has identified the following five principal geographic regions as its reporting segments: United States, primarily Gulf of Mexico. The Company’s vessels in this market support deepwater anchor handling, fast cargo transport, general cargo transport, well intervention, work-over, decommissioning, and diving support operations. Africa, primarily West Africa. The Company’s vessels in this area generally support projects for major oil companies, primarily in Angola and Nigeria. Middle East and Asia. The Company’s vessels in this area generally support exploration, personnel transport and seasonal construction activities in Egypt, Israel, Malaysia and countries along the Arabian Gulf and Arabian Sea, such as Saudi Arabia, the United Arab Emirates and Qatar. Latin America. As of December 31, 2019, 34 vessels were located in this region, including four owned and 30 joint-ventured. Of these joint-ventured vessels, (i) 16 are owned by Mantenimiento Express Maritimo, S.A.P.I. de C.V. (“MexMar”), a joint venture company that is 49% owned by SEACOR Marine International LLC (“SMI”), a wholly owned subsidiary of SEACOR Marine, and 51% owned by subsidiaries of Proyectos Globales de Energía y Servicios CME, S.A. de C.V. (“CME”), (ii) 13 of such vessels are owned by MEXMAR Offshore International LLC (“MEXMAR Offshore”), a joint venture company that is 49% owned by SMI and 51% owned by a subsidiary of CME and (iii) one is owned by SEACOSCO. These vessels, consisting of a fleet of FSVs, supply, specialty and liftboat vessels, provide support for exploration and production activities in Mexico, Brazil and Guyana. From time to time, the Company’s vessels also work in Trinidad and Tobago, and Colombia. Europe, primarily North Sea. As of December 31, 2019, 43 vessels were located in this region supporting the construction and maintenance of offshore wind turbines, including 37 owned and six joint ventured. On December 2, 2019, the Company completed the sale of its North Sea standby safety business, comprised of 18 emergency response and rescue vessels (“ERRVs”) related vessels located in the North Sea providing standby safety and supply services The Spin-off. SEACOR Marine was previously a subsidiary of SEACOR Holdings Inc. (along with its consolidated subsidiaries, other than SEACOR Marine, collectively referred to as “SEACOR Holdings”). On June 1, 2017, SEACOR Holdings completed a spin-off of SEACOR Marine by way of a pro rata dividend of SEACOR Marine’s Common Stock, all of which was then held by SEACOR Holdings, to SEACOR Holdings’ shareholders of record as of May 22, 2017 (the “Spin-off”). SEACOR Marine entered into certain agreements with SEACOR Holdings to govern SEACOR Marine’s relationship with SEACOR Holdings following the Spin-off, including a Distribution Agreement, two Transition Services Agreements, an Employee Matters Agreement and a Tax Matters Agreement. Immediately following the Spin-off, SEACOR Marine began to operate as an independent, publicly traded company.
Basis of Consolidation	Basis of Consolidation. The consolidated financial statements include the accounts of SEACOR Marine and its controlled subsidiaries. Control is generally deemed to exist if the Company has greater than 50% of the voting rights of a subsidiary. All significant intercompany accounts and transactions are eliminated in the combination and consolidation. 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% or less owned companies that it does not control but has the ability to exercise significant influence over the operating and financial policies of the business venture. Significant influence is generally deemed to exist if the Company has between 20% and 50% of the voting rights of a business venture, but may exist when the Company’s ownership percentage is less than 20%. In certain circumstances, the Company may have an economic interest in excess of 50% but may not control and consolidate the business venture. Conversely, the Company may have an economic interest less than 50% but may control and consolidate the business venture. The Company reports its investments in and advances to these business ventures in the accompanying consolidated balance sheets as investments, at equity, and advances to 50% or less owned companies. The Company reports its share of earnings from investments in 50% or less owned companies in the accompanying consolidated statements of loss as equity in earnings (losses) of 50% or less owned companies, net of tax. The Company employs the cost method of accounting for investments in 50% or less owned companies it does not control or exercise significant influence. These investments in private companies are carried at cost and are adjusted only for capital distributions and other-than-temporary declines in fair value. Certain reclassifications were made to previously reported amounts in the consolidated financial statements and notes thereto to make them consistent with the current period presentation.
Use of Estimates	Use of Estimates. The preparation of financial statements in conformity with accounting principles generally accepted in the U.S. requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Such estimates include those related to deferred revenues, allowance for doubtful accounts, useful lives of property and equipment, impairments, income tax provisions and certain accrued liabilities. Actual results could differ from estimates and those differences may be material.
Revenue Recognition	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 to three years and are typically billed on a monthly basis. The Company transfers control of the service to the customer and satisfies its performance obligation over the term of the contract, and therefore recognized revenue over the term of the contract while related costs are expensed as incurred. Revenue that does not meet these criteria is deferred until the criteria is met and such revenue is considered a contract liability. Contract liabilities, which are included in other current liabilities in the accompanying consolidated balance sheets, for the years ended December 31 were as follows (in thousands): 2019 2018 2017 Balance at beginning of year $ 1,327 $ 10,104 $ 6,953 Revenues deferred during the year 8,164 3,600 4,699 Revenues recognized during the year (4,705 ) (12,377 ) (1,548 ) Balance at end of year $ 4,786 $ 1,327 $ 10,104 As of December 31, 2019, the Company deferred revenues of $4.8 million primarily related to $2.0 million of prepaid vessel management fees, and $1.8 million related to the time charter of offshore support vessels to customers from which collections were not reasonably assured. 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 also participate in pooling arrangements. In a pooling arrangement, the time charter revenues of certain of the Company’s vessels are shared with the time charter revenues of certain vessels of similar type owned by non-affiliated vessel owners based upon an agreed formula. On January 9, 2019, the only active pooling arrangement was terminated, and three FSV’s were purchased by the Company. Contract or charter durations may range from several days to several years. Charters vary in length from short-term to multi-year periods, many with cancellation clauses and without early termination penalties. As a result of options and frequent renewals, the stated duration of charters may have little correlation with the length of time the vessel is contracted to provide services to a particular customer.
Cash Equivalents	Cash Equivalents. The Company considers all highly liquid investments with an original maturity of three months or less, when purchased, to be cash equivalents. Cash equivalents consist of U.S. treasury securities, money market instruments, time deposits and overnight investments.
Restricted Cash	Restricted Cash. Restricted cash primarily relates to banking facility requirements. For the year ended December 31, cash, cash equivalents and restricted cash consists of: 2019 2018 Cash $ 83,943 $ 91,597 Cash equivalents — — Restricted cash 3,104 1,657 Total $ 87,047 $ 93,254
Marketable Securities	Marketable Securities. Marketable equity securities with readily determinable fair values and debt securities are reported in the accompanying consolidated balance sheets as marketable securities. These investments are stated at fair value, as determined by their market observable prices, with both realized and unrealized gains and losses reported in the accompanying consolidated statements of loss as marketable security losses, net. Short sales of marketable securities are stated at fair value in the accompanying consolidated balance sheets with both realized and unrealized losses reported in the accompanying consolidated statements of loss as marketable security gains (losses), net. Marketable securities are classified as trading securities for financial reporting purposes with gains and losses reported as operating activities in the accompanying consolidated statements of cash flows.
Trade and Other Receivables	Trade and Other Receivables. Customers are primarily major integrated national and international oil companies, large independent oil and natural gas exploration and production companies, and offshore windfarm operations. Customers are granted credit on a short-term basis and the related credit risks are minimal. Other receivables consist primarily of operating expenses the Company incurs in relation to vessels it manages for other entities, as well as insurance and income tax receivables. The Company routinely reviews its receivables and makes provisions for probable doubtful accounts; however, those provisions are estimates and actual results may materially differ from those estimates. Trade receivables are deemed uncollectible and are removed from accounts receivable and the allowance for doubtful accounts when collection efforts have been exhausted.
Derivative Instruments	Derivative Instruments. The Company accounts for derivatives through the use of a fair value concept whereby all of the Company’s derivative positions are stated at fair value in the accompanying consolidated balance sheets. Realized and unrealized gains and losses on derivatives not designated as hedges are reported in the accompanying consolidated statements of loss as Derivative gains (losses), net. Realized and unrealized gains and losses on derivatives designated as fair value hedges are recognized as corresponding increases or decreases in the fair value of the underlying hedged item to the extent they are effective, with any ineffective portion reported in the accompanying consolidated statements of loss as Derivative gains (losses), net. Realized and unrealized gains and losses on derivatives designated as cash flow hedges are reported as a component of other comprehensive loss in the accompanying consolidated statements of comprehensive loss to the extent they are effective and reclassified into earnings on the same line item associated with the hedged transaction and in the same period the hedged transaction affects earnings. Any ineffective portions of cash flow hedges are reported in the accompanying consolidated statements of loss as Derivative gains (losses), net. Realized and unrealized gains and losses on derivatives designated as cash flow hedges that are entered into by the Company’s 50% or less owned companies are also reported as a component of the Company’s other comprehensive loss in proportion to the Company’s ownership percentage, with reclassifications and ineffective portions being included in Equity in earnings (losses) of 50% or less owned companies, net of tax, in the accompanying consolidated statements of loss.
Concentrations of Credit Risk	Concentrations of Credit Risk. The Company is exposed to concentrations of credit risk associated with its cash and cash equivalents, restricted cash, construction reserve funds and derivative instruments. The Company minimizes its credit risk relating to these positions by monitoring the financial condition of the financial institutions and counterparties involved and by primarily conducting business with large, well-established financial institutions and diversifying its counterparties. The Company does not currently anticipate nonperformance by any of its significant counterparties. The Company is also exposed to concentrations of credit risk relating to its receivables due from customers described above. The Company does not generally require collateral or other security to support its outstanding receivables. The Company minimizes its credit risk relating to receivables by performing ongoing credit evaluations and, to date, credit losses have not been material.
Inventories	Inventories. Inventories, which consist of fuel and supplies, are stated at the lower of cost (using the first-in, first-out method) or market. The Company records write-downs, as needed, to adjust the carrying amount of inventories to the lower of cost or market. In the year ended December 31, 2019, 2018 and 2017, there were no inventory reserves.
Property and Equipment	Property and Equipment. Equipment, stated at cost, is depreciated using the straight-line method over the estimated useful life of the asset to an estimated salvage value. With respect to offshore support vessels, the estimated useful life is typically based upon a newly built vessel being placed into service and represents the point at which it is typically not justifiable for the Company to continue to operate the vessel in the same or similar manner. From time to time, the Company may acquire older vessels that have already exceeded the Company’s useful life policy, in which case the Company depreciates such vessels based on its best estimate of remaining useful life, typically the next regulatory survey or certification date. As of December 31, 2019, the estimated useful life (in years) of each of the Company’s major categories of new offshore support vessels was as follows: 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 was as follows (in thousands): Historical Cost (1) Accumulated Depreciation Net Book Value 2019 Offshore support vessels: AHTS (2) $ 94,078 $ (73,095 ) $ 20,983 FSV (3) 388,460 (101,295 ) 287,165 Supply 44,958 (8,471 ) 36,487 Specialty 14,805 (10,466 ) 4,339 Liftboats 327,028 (93,166 ) 233,862 Crew transfer 82,645 (54,358 ) 28,287 General machinery and spares 7,650 (7,648 ) 2 Other (4) 17,354 (10,463 ) 6,891 $ 976,978 $ (358,962 ) $ 618,016 2018 Offshore support vessels: AHTS (2) $ 197,344 $ (168,731 ) $ 28,613 FSV (3) 404,310 (98,580 ) 305,730 Supply 64,284 (37,202 ) 27,082 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 (4) 13,443 (9,562 ) 3,881 $ 1,116,583 $ (461,399 ) $ 655,184 (1) Includes property and equipment acquired in business acquisitions at acquisition date fair value, and net of the impact of recognized impairment charges. (2) Anchor Handling Towing (“AHTS”) (3) Fast support vessels (“FSVs”). ( 4 ) Includes land, buildings, leasehold improvements, vehicles and other property and equipment. Depreciation and amortization expense from continuing operations totaled $64.0 million, $68.8 million and $60.3 million in 2019, 2018 and 2017, respectively. On December 2, 2019, the Company completed the sale of its North Sea standby business, comprised of 18 ERRVs with a net book value of $24.3 million. Depreciation and amortization expense totaled $3.5 million, $3.4 million and $2.5 million in 2019, 2018 and 2017, respectively. 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 $1.5 million, $2.4 million and $3.6 million in 2019, 2018 and 2017, respectively.
Impairment of Long-Lived Assets and Impairment of 50% or Less Owned Companies	Impairment of Long-Lived Assets. The Company performs an impairment analysis of long-lived assets used in operations, including intangible assets, when indicators of impairment are present. These indicators may include a significant decrease in the market price of a long-lived asset or asset group, a significant adverse change in the extent or manner in which a long-lived asset or asset group is being used or in its physical condition, or a current period operating or cash flow loss combined with a history of operating or cash flow losses or a forecast that demonstrates continuing losses associated with the use of a long-lived asset or asset group. If the carrying values of the assets are not recoverable, as determined by their estimated future undiscounted cash flows, the estimated fair value of the assets or asset groups are compared to their current carrying values and impairment charges are recorded if the carrying value exceeds fair value. As a result of the difficult conditions experienced in the offshore oil and natural gas markets beginning in the second half of 2014 and the corresponding reductions in utilization and rates per day worked of its fleet, the Company identified indicators of impairment and recognized impairment charges primarily associated with its AHTS fleet, its liftboat fleet, certain specialty vessels, vessels removed from service and goodwill. When reviewing its fleet for impairment, the Company groups vessels with similar operating and marketing characteristics, including cold-stacked vessels expected to return to active service, into vessel classes. All other vessels, including vessels retired and removed from service, are evaluated for impairment on a vessel by vessel basis. During the year ended December 31, 2019, the Company recorded non-cash impairment charges of $12.0 million primarily related to four anchor-handling towing supply (“AHTS”) vessels previously removed from service and adjusted to scrap value, and four fast support vessels (“FSV”) each of which has been adjusted to indicative sales price, and two leased-in vessels (one AHTS and one platform supply vessel “PSV”), adjusted for indicative future cash flows . During the year ended December 31, 2018, the Company recorded non-cash impairment charges of $14.6 million primarily associated with its AHTS fleet (four owned vessels and three leased-in vessels) and one specialty vessel. During the year ended December 31, 2017, the Company recorded non-cash impairment charges of $27.5 million primarily associated with its AHTS vessels, one leased-in supply vessel removed from service as it is not expected to be marketed prior to the expiration of its lease, one owned FSV removed from service and two owned in-service specialty vessels. Estimated fair values for the Company’s owned vessels were established by independent appraisers and other market data such as recent sales of similar vessels (see Note 11). If market conditions further decline from the depressed utilization and rates per day worked experience over the last three years, fair values based on future appraisals could decline significantly. The Company’s other vessel classes and other individual vessels in active service and cold-stacked status, for which no impairment was deemed necessary, have generally experienced a less severe decline in utilization and rates per day worked based on specific market factors. The market factors include vessels with more general utility to a broad range of customers (e.g., FSVs), vessels required for customers to meet regulatory mandates and operating under multiple year contracts or vessels that service customers outside of the offshore oil and natural gas market (e.g., CTVs). For vessel classes and individual vessels with indicators of impairment but not recently impaired as of December 31, 2019, the Company has estimated that their future undiscounted cash flows exceed their current carrying values. The Company’s estimates of future undiscounted cash flows are highly subjective as utilization and rates per day worked are uncertain, including the timing of an estimated market recovery in the offshore oil and natural gas markets and the timing and cost of reactivating cold-stacked vessels. If market conditions decline further, changes in the Company’s expectations on future cash flows may result in recognizing additional impairment charges related to its long-lived assets in future periods. Impairment of 50% or Less Owned Companies. Investments in 50% or less owned companies are reviewed periodically to assess whether there is an other-than-temporary decline in the carrying value of the investment. In its evaluation, the Company considers, among other items, recent and expected financial performance and returns, impairments recorded by the investee and the capital structure of the investee. When the Company determines the estimated fair value of an investment is below carrying value and the decline is other-than-temporary, the investment is written down to its estimated fair value. Actual results may vary from the Company’s estimates due to the uncertainty regarding projected financial performance, the severity and expected duration of declines in value, and the available liquidity in the capital markets to support the continuing operations of the investee, among other factors. Although the Company believes its assumptions and estimates are reasonable, the investee’s actual performance compared with the estimates could produce different results and lead to additional impairment charges in future periods. No impairment charges of investments in 50% or less owned companies were incurred for the year ended December 31, 2019. During the years ended 2018 and 2017, the Company recognized impairment charges of $1.2 million and $8.8 million, respectively, net of tax, related to its 50% or less owned companies (see Note 5).
Business Combinations	Business Combinations. The Company recognizes 100% of the fair value of assets acquired, liabilities assumed, and noncontrolling interests when the acquisition constitutes a change in control of the acquired entity. Shares issued in consideration for a business combination, contingent consideration arrangements and pre-acquisition loss and gain contingencies are all measured and recorded at their acquisition-date fair value. Subsequent changes to fair value of contingent consideration arrangements are generally reflected in earnings. Acquisition-related transaction costs are expensed as incurred and any changes in an acquirer’s existing income tax valuation allowances and tax uncertainty accruals are recorded as an adjustment to income tax expense. The operating results of entities acquired are included in the accompanying consolidated statements of loss from the date of acquisition (see Note 3).
Debt Discount and Issue Costs	Debt Discount and Issue Costs . Debt discounts and costs incurred in connection with the issuance of debt are amortized over the life of the related debt using the effective interest rate method for term loans and straight-line method for revolving credit facilities and are included in interest expense in the accompanying consolidated statements of loss.
Self-insurance Liabilities	Self-insurance Liabilities . The Company maintains marine hull, liability and war risk, general liability, workers compensation and other insurance customary in the industry in which it operates. Both the marine hull and liability policies have annual aggregate deductibles. Marine hull annual aggregate deductibles are accrued as claims are incurred while marine liability annual aggregate deductibles are accrued based on historical loss experience. Exposure to the health benefit plans are limited by maintaining stop-loss and aggregate liability coverage. To the extent that estimated self-insurance losses, including the accrual of annual aggregate deductibles, differ from actual losses realized, the Company’s insurance reserves could differ significantly and may result in either higher or lower insurance expense in future periods.
Income Taxes	Income Taxes . Deferred income tax assets and liabilities have been provided in recognition of the income tax effect attributable to the book and tax basis differences of assets and liabilities reported in the accompanying consolidated financial statements. Deferred tax assets or liabilities are provided using the enacted tax rates expected to apply to taxable income in the periods in which they are expected to be settled or realized. Interest and penalties relating to uncertain tax positions are recognized in interest expense and administrative and general, respectively, in the accompanying consolidated statements of loss. The Company records a valuation allowance to reduce its deferred tax assets if it is more likely than not that some portion or all of the deferred tax assets will not be realized. 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 be subject to challenges from tax authorities regarding the amount of taxes due for the Company. These challenges may alter the timing or amount of taxable income or deductions. As part of the calculation of income tax expense, the Company determines whether the benefits of its tax positions are at least more likely than not of being sustained based on the technical merits of the tax position. For tax positions that are more likely than not of being sustained, the Company accrues the largest amount of the tax benefit that is more likely than not of being sustained. Such accruals require management to make estimates and judgments with respect to the ultimate outcome of its tax benefits and actual results could vary materially from these estimates.
Deferred Gains - Vessel Sale-Leaseback Transactions and Financed Vessel Sales	Deferred Gains - Vessel Sale-Leaseback Transactions and Financed Vessel Sales . Prior to the implementation of ASC 842, the Company entered into vessel sale-leaseback transactions with finance companies or provided seller financing on sales of its vessels to third-parties or to 50% or less owned companies. A portion of the gains realized from these transactions was not immediately recognized in income but rather was recorded in the accompanying consolidated balance sheets in deferred gains and other liabilities. In sale-leaseback transactions, gains were deferred to the extent of the present value of future minimum lease payments and were amortized as reductions to rental expense over the applicable lease terms (see Note 7). When the Company determines that future cash inflows do not support future lease cash obligations, the Company records an impairment expense for the amount of the cash flow shortage of all future lease costs, costs to maintain the vessel to the end of the lease term, and costs to return the vessel to its owner, less the amount of any unamortized deferred gains. In financed vessel sales, gains were deferred to the extent that the repayment of purchase notes were dependent on the future operations of the sold vessels and were amortized based on cash received from the buyers. Unamortized deferred gains for four vessels under sale-leaseback agreements were fully recognized as an adjustment to Retained Earnings with the implementation of the new leasing standard (see Note 7). Deferred gain activity related to these transactions for the years ended December 31 was as follows (in thousands): 2019 2018 2017 Balance at beginning of year $ 11,026 $ 23,553 $ 32,035 Amortization of deferred gains included in operating expenses as reduction to rental expense — (8,037 ) (8,118 ) Reclass of gain to Retained Earnings (11,026 ) — — 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 Deferred Gains - Vessel Sales to the Company’s 50% or Less Owned Companies. A portion of the gains realized from non-financed sales of the Company’s vessels to its 50% or less owned companies has been deferred and recorded in the accompanying consolidated balance sheets in deferred gains and other liabilities. In most instances, the sale of a Company vessel to a 50% or less owned company is considered a sale of a business in which the Company relinquishes control to its 50% or less owned company resulting in gain recognition; however, the Company defers gains to the extent of any uncalled capital commitment it has with the 50% or less owned company. Deferred gain activity related to these transactions for the years ended December 31 was as follows (in thousands): 2019 2018 2017 Balance at beginning of year $ 793 $ 1,453 $ 1,875 Amortization of deferred gains included in losses on asset dispositions and impairments, net — (25 ) — Other (793 ) (635 ) (422 ) Balance at end of year $ — $ 793 $ 1,453
Foreign Currency Translation	Foreign Currency Translation. The assets, liabilities and results of operations of certain consolidated subsidiaries are measured using their functional currency, which is the currency of the primary foreign economic environment in which they operate. Upon consolidating these subsidiaries with the Company, their assets and liabilities are translated to U.S. dollars at currency exchange rates as of the consolidated balance sheet dates and their revenues and expenses are translated at the weighted average currency exchange rates during the applicable reporting periods. Translation adjustments resulting from the process of translating these subsidiaries’ financial statements are reported in other comprehensive loss in the accompanying consolidated statements of comprehensive loss. Foreign Currency Transactions. Certain consolidated subsidiaries enter into transactions denominated in currencies other than their functional currency. Gains and losses resulting from changes in currency exchange rates between the functional currency and the currency in which a transaction is denominated are included in foreign currency losses, net in the accompanying consolidated statements of loss in the period in which the currency exchange rates change.
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss. The components of accumulated other comprehensive loss were as follows (in thousands): 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, 2016 $ (11,413 ) $ 76 $ (11,337 ) $ (1,614 ) $ (17 ) $ (6,344 ) Other comprehensive (loss) 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 $ (7,225 ) Other comprehensive income (2,277 ) (1,972 ) (4,249 ) (88 ) (12 ) $ (4,349 ) Income tax benefit (expense) — (46 ) (46 ) — — (46 ) Year Ended December 31, 2018 (15,472 ) (1,316 ) (16,788 ) (1,445 ) (11 ) $ (11,620 ) Other comprehensive loss 20,157 (1,994 ) 18,163 — — $ 18,163 Income tax benefit (expense) — 173 173 — — 173 Year Ended December 31, 2019 $ 4,685 $ (3,137 ) $ 1,548 $ (1,445 ) $ (11 ) $ 6,716 (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.
Loss Per Share	Loss Per Share. Basic loss per common share of the Company is computed based on the weighted average number of common shares issued and outstanding during the relevant periods. Diluted loss per common share of the Company is computed based on the weighted average number of common shares issued and outstanding plus the effect of potentially dilutive securities through the application of the treasury stock and if-converted methods. Dilutive securities for this purpose assumes restricted stock grants have vested, common shares have been issued pursuant to the exercise of outstanding stock options and common shares have been issued pursuant to the conversion of the Convertible Senior Notes. For the years ended December 31, 2019, 2018 and 2017, diluted loss per common share of the Company excluded 1,826,966 shares, 2,183,708 shares and 4,070,500 shares, respectively, issuable upon the conversion of the Convertible Senior Notes as the effect of their inclusion in the computation would be anti-dilutive. In addition, for the years ended December 31, 2019 and 2018, diluted loss per common share of the Company excluded 303,609 shares and 192,346 shares, respectively, of restricted stock and 913,569 and 805,566 outstanding stock options as the effect of their inclusion in the computation would be anti-dilutive. In 2019, the Company issued 109,600 performance share awards, of which 91,600 were still outstanding as of December 31, 2019. These performance share awards are not considered outstanding until such time as they would be probable of being exercised, therefore they were not included in the computation of earnings (loss) per share.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards. On May 28, 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers (Topic 606)” to clarify the principles for recognizing revenue and to develop a common revenue standard and disclosure requirements. The standard supersedes previous revenue recognition requirements and industry-specific guidance. Under the standard, revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration the entity expects to receive in exchange for those goods or services. The Company adopted this standard on January 1, 2018 using the modified retrospective approach by recognizing the cumulative effect of initially applying the standard as an adjustment to the opening balance of retained earnings. The Company implemented the necessary changes to its business processes, systems and controls to support recognition and disclosure of this ASU upon adoption. The Company’s revenues are primarily based on leases or rental agreements with customers which are not addressed in the standard. As a result, the adoption of the accounting standard did not have a material effect on the Company’s consolidated financial position, results of operations or cash flows, but did result in increased disclosures related to revenue recognition policies. On February 25, 2016, the FASB issued a comprehensive new leasing standard meant to improve transparency and comparability among companies by requiring lessees to recognize a lease liability and a corresponding lease asset for virtually all lease contracts. It also requires additional disclosures about leasing arrangements. The Company adopted the new standard on January 1, 2019 and applied the transition provisions of the new standard at its adoption date with recognition of a cumulative-effect adjustment to the opening balance of retained earnings. The adoption of the new standard had a material impact on the Company’s consolidated financial position, results of operations and cash flows. The adjustment to the Company’s balance sheet on January 1, 2019 included the addition of $33.7 million of right-of-use assets, $31.9 million in lease liability, and a cumulative-effect adjustment to the opening balance of retained earnings of $1.7 million for certain of its equipment, office and land leases. In addition, unamortized deferred gains for four vessels leased under sale-leaseback arrangements were fully recognized as an adjustment to the opening balance of retained earnings of $8.7 million, net of tax, ($11.0 million deferred gains net of $2.3 million deferred taxes). On October 24, 2016, the FASB issued a new accounting standard, which requires companies to account for the income tax effects of intercompany sales and transfers of assets other than inventory. The Company adopted the new standard on January 1, 2018, resulting in a reduction of $12.1 million to the Company’s opening retained earnings.
New Accounting Pronouncements	New Accounting Pronouncements. On August 28, 2018, the FASB issued ASU 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. The effects of this standard on our financial position or reporting will not be material. On August 29, 2018, the FASB issued ASU No. 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40) On June 30, 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326). This ASU represents a significant change in the Accounting for Credit Losses model by requiring The ASU introduced a new accounting model, the Current Expected Credit Losses model (CECL), which requires earlier recognition of credit losses and additional disclosures related to credit risk. The CECL model utilizes a lifetime expected credit loss measurement objective for the recognition of credit losses for loans and other receivables at the time the financial asset is originated or acquired. The expected credit losses are adjusted each period for changes in expected lifetime credit losses. This model replaces the multiple existing impairment models in current U.S. GAAP, which generally require that a loss be incurred before it is recognized. The new standard will also apply to financial assets arising from revenue transactions such as contract assets and accounts receivables and is effective for fiscal years beginning after December 15, 2019. Management has performed analysis and the new standard will not have a material impact on consolidated financial statements .

Nature of Operations and Acco_3

Nature of Operations and Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Nature Of Operation And Accounting Policies [Abstract]
Schedule of Deferred Revenues	Revenue that does not meet these criteria is deferred until the criteria is met and such revenue is considered a contract liability. Contract liabilities, which are included in other current liabilities in the accompanying consolidated balance sheets, for the years ended December 31 were as follows (in thousands): 2019 2018 2017 Balance at beginning of year $ 1,327 $ 10,104 $ 6,953 Revenues deferred during the year 8,164 3,600 4,699 Revenues recognized during the year (4,705 ) (12,377 ) (1,548 ) Balance at end of year $ 4,786 $ 1,327 $ 10,104
Schedule Of Cash Cash Equivalents And Restricted Cash	For the year ended December 31, cash, cash equivalents and restricted cash consists of: 2019 2018 Cash $ 83,943 $ 91,597 Cash equivalents — — Restricted cash 3,104 1,657 Total $ 87,047 $ 93,254
Schedule of Property and Equipment Useful Life	As of December 31, 2019, the estimated useful life (in years) of each of the Company’s major categories of new offshore support vessels was as follows: Offshore Support Vessels: Crew transfer vessels 10 All other offshore support vessels (excluding crew transfer) 20
Summary of Property and Equipment	The Company’s property and equipment as of December 31 was as follows (in thousands): Historical Cost (1) Accumulated Depreciation Net Book Value 2019 Offshore support vessels: AHTS (2) $ 94,078 $ (73,095 ) $ 20,983 FSV (3) 388,460 (101,295 ) 287,165 Supply 44,958 (8,471 ) 36,487 Specialty 14,805 (10,466 ) 4,339 Liftboats 327,028 (93,166 ) 233,862 Crew transfer 82,645 (54,358 ) 28,287 General machinery and spares 7,650 (7,648 ) 2 Other (4) 17,354 (10,463 ) 6,891 $ 976,978 $ (358,962 ) $ 618,016 2018 Offshore support vessels: AHTS (2) $ 197,344 $ (168,731 ) $ 28,613 FSV (3) 404,310 (98,580 ) 305,730 Supply 64,284 (37,202 ) 27,082 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 (4) 13,443 (9,562 ) 3,881 $ 1,116,583 $ (461,399 ) $ 655,184
Schedule Of Deferred Gain Activity	Deferred gain activity related to these transactions for the years ended December 31 was as follows (in thousands): 2019 2018 2017 Balance at beginning of year $ 11,026 $ 23,553 $ 32,035 Amortization of deferred gains included in operating expenses as reduction to rental expense — (8,037 ) (8,118 ) Reclass of gain to Retained Earnings (11,026 ) — — 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 2019 2018 2017 Balance at beginning of year $ 793 $ 1,453 $ 1,875 Amortization of deferred gains included in losses on asset dispositions and impairments, net — (25 ) — Other (793 ) (635 ) (422 ) Balance at end of year $ — $ 793 $ 1,453
Schedule of Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss. The components of accumulated other comprehensive loss were as follows (in thousands): 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, 2016 $ (11,413 ) $ 76 $ (11,337 ) $ (1,614 ) $ (17 ) $ (6,344 ) Other comprehensive (loss) 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 $ (7,225 ) Other comprehensive income (2,277 ) (1,972 ) (4,249 ) (88 ) (12 ) $ (4,349 ) Income tax benefit (expense) — (46 ) (46 ) — — (46 ) Year Ended December 31, 2018 (15,472 ) (1,316 ) (16,788 ) (1,445 ) (11 ) $ (11,620 ) Other comprehensive loss 20,157 (1,994 ) 18,163 — — $ 18,163 Income tax benefit (expense) — 173 173 — — 173 Year Ended December 31, 2019 $ 4,685 $ (3,137 ) $ 1,548 $ (1,445 ) $ (11 ) $ 6,716

Transformation, Facility Rest_2

Transformation, Facility Restructuring and Severance Charges (Tables)	12 Months Ended
	Dec. 31, 2019
Restructuring And Related Activities [Abstract]
Schedule of Components of Restructuring Charges	The components of restructuring charges year ended December 31, 2019, were as follows (in thousands): United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Latin America Europe (primarily North Sea) Total Transformation Plan Charges Severance $ 2,995 $ — $ 184 $ — $ 200 $ 3,379 Other 307 — 31 1 — 339 Total $ 3,302 $ — $ 215 $ 1 $ 200 $ 3,718
Schedule of Severance and Other Restructuring Charges	The severance and other restructuring charges gave rise to certain liabilities, the components of which are summarized in the following table (in thousands), and largely relate to liabilities accrued as part of the 2019 Transformation Plan that will be paid pursuant to the respective arrangements and statutory requirements. United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Latin America Europe (primarily North Sea) Total Transformation Plan Severance Liability $ 216 $ — $ — $ — $ 33 $ 249 Other Liability — — — — — — Total Liability $ 216 $ — $ — $ — $ 33 $ 249
Schedule of Cumulative Restructuring and Reorganization Cost Incurred to Date, Estimated Remaining and to be Incurred	The following table is a summary of the cumulative restructuring and reorganization cost incurred in operating charges and the estimated remaining restructuring and reorganization costs to be incurred as of December 31, 2019 (in thousands). 2019 2020 Total One-time termination benefits $ 3,379 $ 2,014 $ 5,393 Professional and other 339 — 339 Total restructuring and reorganization costs incurred and to be incurred $ 3,718 $ 2,014 $ 5,732

Business Acquisitions (Tables)

Business Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Schedule of Allocation of Purchase Price for Company's Acquisitions	The allocation of the purchase price for the Company’s acquisitions for the years ended December 31 was as follows (in thousands): 2018 Trade and other receivables $ — Other current assets 211 Investments, at Equity, and Advances to 50% or Less Owned Companies — Property and Equipment 140,257 Accounts payable — Other current liabilities — Long-Term Debt (106,640 ) Other — Minority Interest (18,828 ) Purchase price (1) $ 15,000 (1) The Company did not have any acquisitions requiring purchase price allocation for the year ended December 31, 2019. Purchase price in 2018 was used to pay MOI’s debtor-in-possession obligations.

Equipment Acquisitions and Di_2

Equipment Acquisitions and Dispositions (Tables)	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Schedule of Vessel Acquired and Disposed	2019 (1) 2018 2017 FSV 2 — 6 Supply 2 — 5 Liftboat — 6 — CTV 2 2 — 6 8 11 (1) Excludes three FSVs purchased from managed entities, one crew transfer vessel sold upon completion and one ERRV purchased from a joint venture. 2019 (1) 2018 (2) 2017 (3) AHTS 1 1 — FSV 5 9 — Supply 5 — 1 Crew transfer — 1 — Liftboats 3 2 2 14 13 3 (1) Excludes the sale of (i) 18 ERRV vessels from the sale of the Company North Sea Standby Safety business, (ii) one crew transfer vessel to the joint venture FRS Windcat Offshore Logistics, (iii) one FSV to the joint venture OVH, (iv) one FSV to a third party with the Company continuing to manage the vessel, (v) one ERRV from discontinued operations and (vi) six vessels that were previously removed from service (five AHTS vessels and one specialty vessel). (2) Excludes three ERRVs from discontinued operations (3) Excludes one ERRV from discontinued operations.

Investments, at Equity, and A_2

Investments, at Equity, and Advances to 50% or Less Owned Companies (Tables)	12 Months Ended
	Dec. 31, 2019
Schedule Of Investments [Abstract]
Equity Method Investments	Investments, at equity, and advances to 50% or less owned companies as of December 31 were as follows (in thousands): Ownership 2019 2018 MexMar 49.0 % $ 54,249 $ 53,840 SEACOSCO 50.0 % 23,926 28,002 OSV Partners 30.4 % 10,669 11,087 SEACOR Marlin 49.0 % 7,929 7,579 MEXMAR Offshore (1) 49.0 % — 4,900 Offshore Vessel Holdings 49.0 % 4,052 4,900 Dynamic Offshore Drilling 19.0 % — 2,263 Nautical Power 50.0 % — — Other 20.0% — 50.0% 4,396 9,202 $ 105,221 $ 121,773 (1) This joint venture holds the investment in UP Offshore Combined Condensed Financial Information of Other Investees. Summarized financial information of the Company’s other investees, at equity, as of and for the years ended December 31 was as follows (in thousands): 2019 2018 Current assets $ 108,238 $ 99,400 Noncurrent assets 618,745 567,628 Current liabilities 106,742 59,912 Noncurrent liabilities 338,836 325,700 2019 2018 2017 Operating Revenues $ 142,327 $ 109,636 $ 147,360 Costs and Expenses: Operating and administrative 119,767 77,952 78,025 Depreciation 28,800 26,443 30,499 148,567 104,395 108,524 Loss on Asset Dispositions and Impairments, Net (166 ) (89 ) — Operating Income $ (6,406 ) $ 5,152 $ 38,836 Net (Loss) Income(1) $ (36,341 ) $ (13,945 ) $ 13,189

Construction Reserve Funds (Tab

Construction Reserve Funds (Tables)	12 Months Ended
	Dec. 31, 2019
Restricted Cash And Investments [Abstract]
Schedule of Construction Reserve Fund Transactions	Construction reserve fund transactions for the years ended December 31 were as follows (in thousands): 2019 2018 2017 Withdrawals $ (15,168 ) $ (17,300 ) $ (39,163 ) Deposits — — 6,315 $ (15,168 ) $ (17,300 ) $ (32,848 )

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Summary of Future Minimum Payments For Operating Leases	As of December 31, 2019, future minimum payments for operating leases for the years ended December 31 were as follows (in thousands): 2020 $ 15,355 2021 7,128 2022 668 2023 621 2024 696 Years subsequent to 2024 4,437 28,905 Interest component (3,984 ) 24,921 Current portion of long-term operating lease liabilities 15,099 Long-term operating lease liabilities $ 9,822
Summary of Components of Leases Expense	For the year ended December 31, 2019, the components of lease expense were as follows (in thousands): 2019 Operating lease expense $ 13,639 Short-term lease expense (lease duration of twelve months or less at lease commencement) 2,519 $ 16,158
Summary of Other Information Related to Operating Leases	For the year ended December 31, 2019, other information related to operating leases were as follows (in thousands except weighted average data): 2019 Operating cash flows from operating leases $ 19,339 Right-of-use assets obtained for operating lease liabilities $ 35,246 Weighted average remaining lease term, in years 4.7 Weighted average discount rate 4.1 %

Long-term Debt (Tables)

Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Long-term Debt Obligations	The Company’s long-term debt obligations as of December 31 were as follows (in thousands): 2019 2018 Convertible Senior Notes $ 125,000 $ 125,000 SEACOR Marine Foreign Holdings Loan Facility 113,750 126,750 Falcon Global USA Term Loan Facility 102,349 109,099 Sea-Cat Crewzer III Term Loan Facility 24,128 25,989 Windcat Workboats Facilities 24,730 24,850 Falcon Global USA Revolver 15,000 15,000 SEACOR 88/888 Term Loan 11,000 11,000 SEACOR Alps 10,534 — BNDES Equipment Construction Finance Notes 3,332 5,284 429,823 442,972 Portion due within one year (17,802 ) (16,812 ) Debt discount (26,343 ) (32,005 ) Issue costs (5,427 ) (6,301 ) $ 380,251 $ 387,854
Schedule of Long-term Debt Maturities	The Company’s contractual long-term debt maturities for the years ended December 31 were as follows (in thousands): 2020 $ 17,802 2021 51,789 2022 26,007 2023 231,674 2024 90,800 Years subsequent to 2024 11,752 $ 429,823

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	Loss before income tax benefit and equity in earnings (losses) of 50% or less owned companies derived from U.S. and foreign companies for the years ended December 31 were as follows (in thousands): 2019 2018 2017 United States $ (71,833 ) $ (72,540 ) $ (90,696 ) Foreign (22,025 ) (29,466 ) (45,879 ) Eliminations 11,022 8,782 18,785 $ (82,836 ) $ (93,224 ) $ (117,790 )
Schedule of Components of Income Tax Expense (Benefit)	The components of income tax expense (benefit) for the years ended December 31 were as follows (in thousands): 2019 2018 2017 Current: Federal $ (6 ) $ 5,987 $ (16,705 ) State (78 ) 3 (42 ) Foreign 5,039 3,393 3,343 4,955 9,383 (13,404 ) Deferred: Federal (12,594 ) (21,466 ) (60,750 ) State (224 ) (1,404 ) (172 ) Foreign (49 ) 133 (84 ) (12,867 ) (22,737 ) (61,006 ) $ (7,912 ) $ (13,354 ) $ (74,410 )
Schedule of Effective Income Tax Rate Reconciliation	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: 2019 2018 2017 Statutory rate (21.0 )% (21.0 )% (35.0 )% U.S. federal income tax law changes — % — % (37.3 )% SEACOR Holdings share awards to Company personnel — % 0.2 % 2.3 % Non-deductible expenses — % — % 1.8 % Exclusion of foreign subsidiaries with accumulated losses and withholding tax 7.2 % 9.5 % 3.1 % Noncontrolling interests 1.8 % (1.5 )% 1.7 % State taxes (0.3 )% (1.5 )% (0.2 )% Return to provision 2.9 % (0.5 )% 0.4 % Other (0.2 )% 0.5 % — % Effective Tax Rate (9.6 )% (14.3 )% (63.2 )%
Schedule of Deferred Tax Assets and Liabilities	The components of net deferred income tax liabilities as of December 31 were as follows (in thousands): 2019 2018 Deferred tax liabilities: Property and equipment $ 63,827 $ 65,880 Investments in 50% or Less Owned Companies 3,039 3,040 Other 10,953 7,792 Total deferred tax liabilities 77,819 76,712 Deferred tax assets: Federal Net Operating Loss Carryforwards 28,664 20,974 Other 16,561 11,677 45,225 32,651 Valuation Allowance (1,311 ) (624 ) Total deferred tax assets 43,914 32,027 Net deferred tax liabilities $ 33,905 $ 44,685

Derivative Instruments and He_2

Derivative Instruments and Hedging Strategies (Tables)	12 Months Ended
	Dec. 31, 2019
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Schedule of Fair Value of Derivative Assets and Liabilities	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 were as follows (in thousands): 2019 2018 Balance Sheet Classification Derivative Asset Derivative Liability Derivative Asset Derivative Liability Derivatives designated as hedging instruments: Interest rate swap agreements (cash flow hedges) Current $ — $ 3,009 $ — $ 1,659 — 3,009 — 1,659 Derivatives not designated as hedging instruments: Conversion option liability on Convertible Senior Notes Long-Term — 5,205 — 5,276 $ — $ 8,214 $ — $ 6,935
Effect of Derivative Instruments on Other Comprehensive Income (Loss)	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 2019 2018 2017 Interest rate swap contracts $ (1,901 ) $ (1,939 ) $ 214 Joint venture interest rate swap contracts (645 ) (76 ) 389 Gain (Loss) Reclassified from OCI into Income (Effective Portion) Location of Gain 2019 2018 2017 Interest expense $ 552 $ 31 118
Schedule of Gains (Losses) on Derivative Instruments not Designated as Hedging Instruments	The Company recognized gains (losses) on derivative instruments not designated as hedging instruments for the years ended December 31 as follows (in thousands): Derivative gains (losses), net 2019 2018 2017 Conversion option liability on Convertible Senior Notes $ 71 $ 1,556 $ 20,422 Interest rate swap agreements — 1,298 46 Forward currency exchange, option and future contracts — — (212 ) $ 71 $ 2,854 $ 20,256

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis	The Company’s financial assets and liabilities as of December 31 that are measured at fair value on a recurring basis were as follows (in thousands): Level 1 Level 2 Level 3 (1) 2019 ASSETS Construction reserve funds $ 12,893 $ — $ — LIABILITIES Derivative instruments (included in other current liabilities) — 3,009 — Conversion Option Liability on Convertible Senior Notes — — 5,205 2018 ASSETS Derivative instruments (included in other receivables) $ — $ 419 $ — Construction reserve funds 28,221 — — LIABILITIES Derivative instruments (included in other current liabilities) — 1,659 — Conversion Option Liability on Convertible Senior Notes — — 5,276 (1) For the year ended December 31, 2019, the Company recognized a $0.1 million gain in the fair market valuation of the Convertible Senior Notes, as valued by an independent third-party.
Schedule of Estimated Fair Values of Financial Assets and Liabilities	The estimated fair value of the Company’s other financial assets and liabilities as of December 31 were as follows (in thousands): Estimated Fair Value Carrying Amount Level 1 Level 2 Level 3 2019 ASSETS Cash, cash equivalents and restricted cash $ 87,047 $ 87,047 $ — $ — Investments, at cost, in 50% or less owned companies (included in other assets) 132 see below LIABILITIES Long-term debt, including current portion 398,053 — 380,815 — 2018 ASSETS Cash, cash equivalents and restricted cash $ 93,254 $ 93,254 $ — $ — Investments, at cost, in 50% or less owned companies (included in other assets) 132 see below LIABILITIES Long-term debt, including current portion 404,666 — 388,949 —
Schedule of Other Assets and Liabilities Measured at Fair Value	The Company’s non-financial assets and liabilities that were measured at fair value during the years ended December 31 were as follows (in thousands): Level 1 Level 2 Level 3 2019 ASSETS Property and equipment: AHTS $ — $ 520 $ — FSV — 1,858 — 2018 ASSETS Property and equipment: AHTS $ — $ 2,000 $ — Liftboats — — 134,775 Specialty — 4,500 —

Noncontrolling Interests in S_2

Noncontrolling Interests in Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2019
Noncontrolling Interest [Abstract]
Schedule of Noncontrolling Interests in the Company's Consolidated Subsidiaries	Noncontrolling interests in the Company’s consolidated subsidiaries as of December 31 were as follows (in thousands): Noncontrolling Interests 2019 2018 Falcon Global Holdings 28.0 % $ 21,119 $ 26,989 Windcat Workboats — (1) — 2,115 Other 1.8 % 313 300 $ 21,432 $ 29,404

Share Based Compensation (Table

Share Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Equity Incentive Plan Transactions	The following transactions have occurred in connection with the Company’s share-based compensation under the 2017 Plan during the years ended December 31: 2019 2018 Director Stock Awards Granted 30,197 19,285 Restricted Stock Activity: Outstanding as of the beginning of year 192,346 121,693 Granted - 2017 Plan 245,400 (1) 120,600 Vested 131,937 49,947 Forfeited 2,200 — Outstanding as of the end of year 303,609 192,346 Stock Option Activity: Outstanding as of the beginning of year 805,566 613,700 Granted - 2017 Plan 230,503 258,491 Exercised 113,750 66,625 Forfeited 8,750 — Outstanding as of the end of year 913,569 805,566 (1) Excludes 91,600 grants of performance-based stock units that are not considered outstanding until such time that they become probable to vest.
Schedule of Restricted Stock Transactions	During the year ended December 31, 2019, the number of shares and the weighted average grant price of restricted stock transactions were as follows: Restricted Stock Number of Shares Weight Average Grant Price Non-Vested as of December 31, 2018 192,346 $ 22.32 Granted 245,400 13.28 Vested 131,937 13.45 Forfeited 2,200 17.26 Non-Vested as of December 31, 2019 303,609 20.46
Schedule of Stock Option Transactions	During the year ended December 31, 2019, the number of shares and the weighted average exercise price on stock option transactions were as follows: Stock Options Number of Shares Weight Average Grant Price Non-Vested as of December 31, 2018 805,566 $ 14.81 Granted 230,503 8.73 Exercised 113,750 13.98 Forfeited 8,750 20.93 Non-Vested as of December 31, 2019 913,569 14.85 Exercisable as of December 31, 2019 (1) 408,075 14.69 (1) The weighted average remaining contractual term is 8.23 years.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	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 year ended December 31, 2017 (in thousands): 2017 Participation in SEACOR Holdings employee benefit plans $ 899 Participation in SEACOR Holdings share award plans 8,383 Shared services allocation for administrative support 1,932 $ 11,214

Major Customers and Segment I_2

Major Customers and Segment Information (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	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 Latin America Europe Continuing Operations Total For the year ended December 31, 2019 Operating Revenues: Time charter $ 38,955 $ 44,160 $ 54,312 $ 11,460 $ 33,414 $ 182,301 Bareboat charter 1,562 — — 3,569 — 5,131 Other 3,806 1,461 1,669 1,390 5,734 14,060 44,323 45,621 55,981 16,419 39,148 201,492 Direct Costs and Expenses: Operating: Personnel 17,491 13,833 16,698 4,459 13,031 65,512 Repairs and maintenance 7,583 4,701 7,182 1,348 3,855 24,669 Drydocking 4,594 490 600 161 3 5,848 Insurance and loss reserves 2,370 1,051 1,449 311 857 6,038 Fuel, lubes and supplies 2,936 3,471 2,904 1,056 960 11,327 Other 393 4,354 3,095 1,182 1,307 10,331 35,367 27,900 31,928 8,517 20,013 123,725 Direct Vessel Profit $ 8,956 $ 17,721 $ 24,053 $ 7,902 $ 19,135 77,767 Other Costs and Expenses: Operating: Leased-in equipment $ 10,894 $ 3,090 $ 173 $ 10 $ 1,991 16,158 Administrative and general 44,726 Depreciation and amortization $ 21,947 $ 10,404 $ 16,400 $ 6,205 $ 9,056 64,012 124,896 Losses on Asset Dispositions and Impairments, Net (5,397 ) Operating Loss $ (52,526 ) As of December 31, 2019 Property and Equipment: Historical cost $ 297,392 $ 207,107 $ 292,446 $ 57,534 $ 122,499 $ 976,978 Accumulated depreciation (157,514 ) (57,136 ) (73,039 ) (16,239 ) (55,034 ) (358,962 ) $ 139,878 $ 149,971 $ 219,407 $ 41,295 $ 67,465 $ 618,016 Total Assets (1) $ 224,229 $ 161,915 $ 250,890 $ 116,736 $ 109,874 $ 863,644 (1) Total assets exclude $145,232 thousand of corporate assets. United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Latin America Europe Continuing Operations Total For the year ended December 31, 2018 Operating Revenues: Time charter $ 38,802 $ 43,847 $ 50,072 $ 17,343 $ 22,286 $ 172,350 Bareboat charter — — — 4,635 — 4,635 Other 14,762 7,661 (887 ) 1,554 3,492 26,582 53,564 51,508 49,185 23,532 25,778 203,567 Direct Costs and Expenses: Operating: Personnel 18,708 16,538 16,806 4,399 10,862 67,313 Repairs and maintenance 5,152 6,330 11,172 1,011 3,368 27,033 Drydocking 1,957 2,085 1,362 128 2,261 7,793 Insurance and loss reserves 2,922 1,096 1,371 495 459 6,343 Fuel, lubes and supplies 3,568 3,826 4,027 1,225 863 13,509 Other 393 4,313 3,980 1,130 467 10,283 32,700 34,188 38,718 8,388 18,280 132,274 Direct Vessel Profit $ 20,864 $ 17,320 $ 10,467 $ 15,144 $ 7,498 71,293 Other Costs and Expenses: Operating: Leased-in equipment $ 8,240 $ 4,281 $ 224 $ 5 $ 489 13,239 Administrative and general 46,454 Depreciation and amortization $ 23,227 $ 10,453 $ 18,762 $ 7,908 $ 8,491 68,841 128,534 Losses on Asset Dispositions and Impairments, Net (11,268 ) Operating Loss $ (68,509 ) As of December 31, 2018 Property and Equipment: Historical cost $ 432,336 $ 184,361 $ 306,897 $ 124,177 $ 68,812 $ 1,116,583 Accumulated depreciation (224,737 ) (55,206 ) (81,378 ) (57,002 ) (43,076 ) (461,399 ) $ 207,599 $ 129,155 $ 225,519 $ 67,175 $ 25,736 $ 655,184 Total Assets (1) $ 351,748 $ 140,335 $ 260,002 $ 137,983 $ 18,217 $ 908,285 (1) Total assets exclude $153,151 thousand of corporate assets, and $41,502 thousand of assets held-for-sale United States (primarily Gulf of Mexico) Africa (primarily West Africa) Middle East and Asia Latin America Europe Continuing Operations Total For the year ended December 31, 2017 Operating Revenues: Time charter $ 18,079 $ 32,866 $ 33,410 $ 2,977 $ 22,990 $ 110,322 Bareboat charter — — — 4,636 — 4,636 Other 4,217 1,080 474 552 2,140 8,463 22,296 33,946 33,884 8,165 25,130 123,421 Direct Costs and Expenses: Operating: Personnel 15,621 13,419 16,883 809 7,881 54,613 Repairs and maintenance 3,594 5,957 9,037 274 2,462 21,324 Drydocking 1,828 2,180 968 — — 4,976 Insurance and loss reserves 3,286 677 1,444 316 306 6,029 Fuel, lubes and supplies 1,485 2,815 3,727 223 496 8,746 Other 249 3,319 5,240 117 208 9,133 26,063 28,367 37,299 1,739 11,353 104,821 Direct Vessel Profit (Loss) $ (3,767 ) $ 5,579 $ (3,415 ) $ 6,426 $ 13,777 18,600 Other Costs and Expenses: Operating: Leased-in equipment $ 8,709 $ 4,317 $ 1,092 $ 5 $ 326 14,449 Administrative and general 49,865 Depreciation and amortization $ 22,060 $ 9,280 $ 17,724 $ 3,608 $ 7,635 60,307 124,621 Losses on Asset Dispositions and Impairments, Net (23,623 ) Operating Loss $ (129,644 ) As of December 31, 2017 Property and Equipment: Historical cost $ 410,475 $ 192,600 $ 326,378 $ 72,484 $ 56,367 $ 1,058,304 Accumulated depreciation (230,636 ) (57,228 ) (100,435 ) (37,281 ) (34,312 ) (459,892 ) $ 179,839 $ 135,372 $ 225,943 $ 35,203 $ 22,055 $ 598,412 Total Assets (1) $ 310,675 $ 140,173 $ 234,471 $ 103,135 $ 13,650 $ 802,104 (1) Total assets exclude $169,346 thousand of corporate assets, and $37,054 thousand of assets held-for-sale.

Supplemental Information for _2

Supplemental Information for Statements of Cash Flows (Tables)	12 Months Ended
	Dec. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Schedule of Supplemental Information	Supplemental information for the years ended December 31 was as follows (in thousands): 2019 2018 2017 Income taxes (paid) refunded, net $ 1,999 $ (316 ) $ 33,773 Interest paid, excluding capitalized interest 22,452 21,031 9,216

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2019
Discontinued Operations And Disposal Groups [Abstract]
Schedule of Assets Held for Sale	Summarized selected operating result of the Company’s assets, previously classified as held for sale were as follows (in thousands): December 31, 2018 Assets from Discontinued Operations: Current assets $ 15,222 Net property and equipment 26,280 41,502 Total current liabilities $ 2,526 For the years ended December 31, 2019 2018 Operating Revenues: Time charter $ 41,214 $ 49,902 Other revenue 45 140 41,259 50,042 Costs and Expenses: Operating 33,836 42,817 Direct Vessel Profit 7,423 7,225 General and Administrative Expenses 4,207 4,524 Lease Expense 60 71 Depreciation 3,504 3,405 (Loss) Gain on Asset Dispositions and Impairments, Net 91 2,521 Operating (Loss) Income (257 ) 1,746 Other Income (Expense) Interest income 11 12 Interest expense (210 ) (465 ) Foreign currency translation loss (75 ) (53 ) (274 ) (506 ) Operating (Loss) Income Before Equity Earnings of 50% or Less Owned Companies, Net of Tax (531 ) 1,240 Income Tax Expense (2 ) 7 Operating (Loss) Income Before Equity Earnings of 50% or Less Owned Companies (529 ) 1,233 Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax 168 137 Net (Loss) Income from Discontinued Operations $ (361 ) $ 1,370

Quarterly Financial Informati_2

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Selected Financial Information for Interim Quarterly Periods	Three Months Ended Dec. 31, Sept. 30, June 30, March 31, 2019 Operating Revenues $ 49,070 $ 54,700 $ 52,812 $ 44,910 Operating Loss (10,497 ) (3,355 ) (17,640 ) (21,034 ) Net (Loss) Income: Continuing Operations (19,176 ) (10,341 ) (31,438 ) (28,273 ) Discontinued Operations (2,742 ) (7,899 ) 1,174 — $ (21,918 ) $ (18,240 ) $ (30,264 ) $ (28,273 ) Net Loss attributable to SEACOR Marine Holdings Inc: $ (20,455 ) $ (18,444 ) $ (28,389 ) $ (25,549 ) Basic and Diluted Loss Per Common Share of SEACOR Marine Holdings Inc. Continuing Operations $ (0.74 ) $ (0.49 ) $ (1.31 ) $ (1.16 ) Discontinued Operations $ (0.12 ) $ (0.29 ) $ 0.10 $ 0.05 $ (0.86 ) $ (0.78 ) $ (1.21 ) $ (1.11 ) 2018 Operating Revenues $ 58,897 $ 58,169 $ 47,871 $ 38,630 Operating Loss (11,253 ) (12,207 ) (20,842 ) (24,206 ) Net (Loss) Income: Continuing Operations (7,780 ) (17,706 ) (26,505 ) (31,430 ) Discontinued Operations (189 ) 1,940 (124 ) (258 ) $ (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 and Diluted Loss Per Common Share of SEACOR Marine Holdings Inc. Continuing Operations $ (0.39 ) $ (0.85 ) $ (1.18 ) $ (1.63 ) Discontinued Operations $ 0.04 $ 0.14 $ (0.01 ) $ (0.01 ) $ (0.35 ) $ (0.71 ) $ (1.19 ) $ (1.64 )

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts (Tables)	12 Months Ended
	Dec. 31, 2019
Valuation And Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts	Description Balance Beginning of Year Charges (Recoveries) to Cost and Expenses Deductions (1) Balance End of Year Year Ended December 31, 2019 Allowance for doubtful accounts (deducted from trade and notes receivable) $ 860 $ (405 ) $ — $ 455 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 (1) Trade receivable amounts deemed uncollectible that were removed from accounts receivable and allowance for doubtful accounts.

Nature of Operations and Acco_4

Nature of Operations and Accounting Policies - Additional Information (Details)		Dec. 02, 2019Vessel	Jan. 01, 2019USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2019USD ($)SegmentVesselshares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)shares	Dec. 20, 2018	Dec. 31, 2016USD ($)
Nature Of Operations And Accounting Policies [Line Items]
Number of reportable segments | Segment					5
Equity method investment, ownership percentage								49.00%
Contract with customer, liability					$ 4,786,000	$ 1,327,000	$ 10,104,000		$ 6,953,000
Prepaid management fees					5,327,000	1,460,000
Inventory reserves					0	0	0
Net book value					618,016,000	655,184,000	598,412,000
Capitalized interest costs, including allowance for funds used during construction, total					1,500,000	2,400,000	3,600,000
Impairment of long-lived assets held-for-use					12,000,000	14,600,000	27,500,000
Equity method investment, other than temporary impairment					$ 0	$ 1,200,000	$ 8,800,000
Incremental common shares attributable to conversion of debt securities, total | shares					1,826,966	2,183,708	4,070,500
Operating Lease, Right-of-Use Asset					$ 17,313,000
Operating Lease, Liability					24,921,000
Deferred taxes					$ 77,819,000	$ 76,712,000
Change in Accounting Principle for Unamortized Deferred Gains
Nature Of Operations And Accounting Policies [Line Items]
Deferred gain net			$ 11,000
Deferred taxes			2,300
Accounting Standards Update 2016-02
Nature Of Operations And Accounting Policies [Line Items]
Operating Lease, Right-of-Use Asset			33,700,000
Operating Lease, Liability			31,900,000
Accounting Standards Update 2016-02 | Change in Accounting Principle for Equipment, Office and Land Leases
Nature Of Operations And Accounting Policies [Line Items]
Cumulative effect on retained earnings, net of tax			1,700,000
Accounting Standards Update 2016-02 | Change in Accounting Principle for Unamortized Deferred Gains
Nature Of Operations And Accounting Policies [Line Items]
Cumulative effect on retained earnings, net of tax			$ 8,700,000
Accounting Standards Update 2016-16
Nature Of Operations And Accounting Policies [Line Items]
Cumulative effect on retained earnings, net of tax				$ 12,100,000
Performance Share Awards
Nature Of Operations And Accounting Policies [Line Items]
Number of shares issued | shares					109,600
Number of shares outstanding | shares					91,600
Restricted Stock
Nature Of Operations And Accounting Policies [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount | shares					303,609	192,346
Employee Stock Option
Nature Of Operations And Accounting Policies [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount | shares					913,569	805,566
Continuing Operations
Nature Of Operations And Accounting Policies [Line Items]
Depreciation, total					$ 64,000,000	$ 68,800,000	$ 60,300,000
Discontinued Operations
Nature Of Operations And Accounting Policies [Line Items]
Depreciation, total					3,500,000	3,400,000	2,500,000
Net book value					24,300,000
Prepaid Vessel Management Fees
Nature Of Operations And Accounting Policies [Line Items]
Prepaid management fees					2,000,000
Geographic Distribution, Domestic
Nature Of Operations And Accounting Policies [Line Items]
Contract with customer, liability					4,800,000
Geographic Distribution, Foreign
Nature Of Operations And Accounting Policies [Line Items]
Contract with customer, liability					$ 1,800,000
Minimum
Nature Of Operations And Accounting Policies [Line Items]
Equity method investment, ownership percentage					20.00%
Minimum | SEACOR Marine Foreign Holdings
Nature Of Operations And Accounting Policies [Line Items]
Equity method investment, ownership percentage					50.00%
Maximum
Nature Of Operations And Accounting Policies [Line Items]
Equity method investment, ownership percentage					50.00%
CME
Nature Of Operations And Accounting Policies [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners					51.00%
MexMar
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels owned | Vessel					16
Equity method investment, ownership percentage					49.00%
SMI
Nature Of Operations And Accounting Policies [Line Items]
Equity method investment, ownership percentage					49.00%
MEXMAR Offshore
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels owned | Vessel					13
Equity method investment, ownership percentage	[1]				49.00%
SEACOSCO
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels owned | Vessel					1
Equity method investment, ownership percentage					50.00%
Latin America
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels | Vessel					34
Number of vessels owned | Vessel					4
Number of vessels joint ventured | Vessel					30
Net book value					$ 41,295,000	67,175,000	35,203,000
Europe
Nature Of Operations And Accounting Policies [Line Items]
Number of vessels | Vessel					43
Number of vessels owned | Vessel					37
Number of vessels joint ventured | Vessel					6
Number of non-wind farm vessels | Vessel		18
Net book value					$ 67,465,000	$ 25,736,000	$ 22,055,000
[1]	This joint venture holds the investment in UP Offshore

Nature of Operations and Acco_5

Nature of Operations and Accounting Policies - Schedule Of Deferred Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Nature Of Operation And Accounting Policies [Abstract]
Balance at beginning of year	$ 1,327	$ 10,104	$ 6,953
Revenues deferred during the year	8,164	3,600	4,699
Revenues recognized during the year	(4,705)	(12,377)	(1,548)
Balance at end of year	$ 4,786	$ 1,327	$ 10,104

Nature of Operations and Acco_6

Nature of Operations and Accounting Policies - Schedule Of Cash, Cash Equivalents And Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Nature Of Operation And Accounting Policies [Abstract]
Cash	$ 83,943	$ 91,597
Restricted cash	3,104	1,657
Total	$ 87,047	$ 93,254

Nature of Operations and Acco_7

Nature of Operations and Accounting Policies - Schedule of Property and Equipment Useful Life (Details)	12 Months Ended
	Dec. 31, 2019
Crew Transfer Vessels
Property Plant And Equipment [Line Items]
Estimated useful life (Year)	10 years
All Other Offshore Support Vessels
Property Plant And Equipment [Line Items]
Estimated useful life (Year)	20 years

Nature of Operations and Acco_8

Nature of Operations and Accounting Policies - Summary of Property and Equipment (Details) - USD ($) $ in Thousands		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Historical cost		$ 976,978	[1]	$ 1,116,583	[1]	$ 1,058,304
Accumulated depreciation		(358,962)		(461,399)		(459,892)
Net book value		618,016		655,184		$ 598,412
Offshore Support Vessels, Anchor Handling Towing Supply
Historical cost	[1],[2]	94,078		197,344
Accumulated depreciation	[2]	(73,095)		(168,731)
Net book value	[2]	20,983		28,613
Fast Support Vessels
Historical cost	[1],[3]	388,460		404,310
Accumulated depreciation	[3]	(101,295)		(98,580)
Net book value	[3]	287,165		305,730
Offshore Support Vessels, Supply
Historical cost	[1]	44,958		64,284
Accumulated depreciation		(8,471)		(37,202)
Net book value		36,487		27,082
Offshore Support Vessels, Specialty
Historical cost	[1]	14,805		25,683
Accumulated depreciation		(10,466)		(20,433)
Net book value		4,339		5,250
Offshore Support Vessels, Liftboats
Historical cost	[1]	327,028		329,473
Accumulated depreciation		(93,166)		(71,887)
Net book value		233,862		257,586
Crew Transfer Vessels
Historical cost	[1]	82,645		73,589
Accumulated depreciation		(54,358)		(46,614)
Net book value		28,287		26,975
General Machinery and Spares
Historical cost	[1]	7,650		8,457
Accumulated depreciation		(7,648)		(8,390)
Net book value		2		67
Property, Plant and Equipment, Other Types
Historical cost	[1],[4]	17,354		13,443
Accumulated depreciation	[4]	(10,463)		(9,562)
Net book value	[4]	$ 6,891		$ 3,881
[1]	Includes property and equipment acquired in business acquisitions at acquisition date fair value, and net of the impact of recognized impairment charges.
[2]	Anchor Handling Towing Supply (“AHTS”)
[3]	Fast support vessels (“FSVs”)
[4]	Includes land, buildings, leasehold improvements, vehicles and other property and equipment.

Nature of Operations and Acco_9

Nature of Operations and Accounting Policies - Schedule of Deferred Gain Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Sale-leaseback and Financed Equipment Sales
Balance at beginning of year	$ 11,026	$ 23,553	$ 32,035
Amortization of deferred gains		(8,037)	(8,118)
Reclass of gain to Retained Earnings	(11,026)
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
Vessel Sales to Fifty Percent or Less Owned Subsidiaries
Balance at beginning of year	793	1,453	1,875
Amortization of deferred gains		(25)
Other	$ (793)	(635)	(422)
Balance at end of year		$ 793	$ 1,453

Nature of Operations and Acc_10

Nature of Operations and Accounting Policies - Schedule of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Balance		$ 554,935	$ 523,166
Other comprehensive (loss) income		18,163	(4,349)	$ 5,375
Income tax benefit (expense)		(173)	46	6,256
Balance		478,924	554,935	523,166
Accumulated Foreign Currency Adjustment Attributable to Parent
Accumulated Other Comprehensive Income Loss [Line Items]
Balance		(15,472)	(13,195)	(11,413)
Other comprehensive (loss) income		20,157	(2,277)	4,397
Income tax benefit (expense)	[1]			(6,179)
Balance		4,685	(15,472)	(13,195)
Accumulated Loss, Net, Cash Flow Hedge, Parent
Accumulated Other Comprehensive Income Loss [Line Items]
Balance		(1,316)	702	76
Other comprehensive (loss) income		(1,994)	(1,972)	703
Income tax benefit (expense)		173	(46)	(77)	[1]
Balance		(3,137)	(1,316)	702
AOCI Attributable to Parent
Accumulated Other Comprehensive Income Loss [Line Items]
Balance		(16,788)	(12,493)	(11,337)
Other comprehensive (loss) income		18,163	(4,249)	5,100
Income tax benefit (expense)		173	(46)	(6,256)	[1]
Balance		1,548	(16,788)	(12,493)
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income Loss [Line Items]
Balance		(1,445)	(1,357)	(1,614)
Other comprehensive (loss) income			(88)	257
Balance		(1,445)	(1,445)	(1,357)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Noncontrolling Interest
Accumulated Other Comprehensive Income Loss [Line Items]
Balance		(11)	1	(17)
Other comprehensive (loss) income			(12)	18
Balance		(11)	(11)	1
AOCI Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income Loss [Line Items]
Balance		(11,620)	(7,225)	(6,344)
Other comprehensive (loss) income		18,163	(4,349)	5,375
Income tax benefit (expense)		173	(46)	(6,256)	[1]
Balance		$ 6,716	$ (11,620)	$ (7,225)
[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

Nature of Operations and Acc_11

Nature of Operations and Accounting Policies - Schedule of Accumulated Other Comprehensive Loss (Parenthetical) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Nature Of Operation And Accounting Policies [Abstract]
Effective income tax rate reconciliation, change in enacted tax rate, amount	$ 4.5

Transformation, Facility Rest_3

Transformation, Facility Restructuring and Severance Charges - Additional Information (Details) - Transformation Plan - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring and related activities, description				The ongoing transformation plan, which began in the third quarter of 2019 and is expected to extend through the second quarter of 2020 (the “Transformation Plan”), includes a workforce reduction, organization restructuring, facility consolidations and other cost reduction measures and efficiency initiatives across the Company’s geographic regions. The Transformation Plan was initiated to reduce the Company’s overall cost structure and workforce to better align with current activity levels of oil and gas exploration and production.
Restructuring charges	$ 400	$ 3,300	$ 3,718
Severance charges			3,379
Other restructuring charges			$ 339

Transformation, Facility Rest_4

Transformation, Facility Restructuring and Severance Charges - Schedule of Components of Restructuring Charges (Details) - Transformation Plan - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2019
Restructuring Cost And Reserve [Line Items]
Severance			$ 3,379
Other			339
Total	$ 400	$ 3,300	3,718
UNITED STATES
Restructuring Cost And Reserve [Line Items]
Severance			2,995
Other			307
Total			3,302
Middle East and Asia
Restructuring Cost And Reserve [Line Items]
Severance			184
Other			31
Total			215
Latin America
Restructuring Cost And Reserve [Line Items]
Other			1
Total			1
Europe
Restructuring Cost And Reserve [Line Items]
Severance			200
Total			$ 200

Transformation, Facility Rest_5

Transformation, Facility Restructuring and Severance Charges - Schedule of Severance and Other Restructuring Charges (Details) - Transformation Plan $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring liability	$ 249
Severance Liability
Restructuring Cost And Reserve [Line Items]
Restructuring liability	249
UNITED STATES
Restructuring Cost And Reserve [Line Items]
Restructuring liability	216
UNITED STATES | Severance Liability
Restructuring Cost And Reserve [Line Items]
Restructuring liability	216
Europe
Restructuring Cost And Reserve [Line Items]
Restructuring liability	33
Europe | Severance Liability
Restructuring Cost And Reserve [Line Items]
Restructuring liability	$ 33

Transformation, Facility Rest_6

Transformation, Facility Restructuring and Severance Charges - Schedule of Cumulative Restructuring and Reorganization Cost Incurred to Date, Estimated Remaining and to be Incurred (Details) $ in Thousands	Dec. 31, 2019USD ($)
Restructuring Cost And Reserve [Line Items]
Total restructuring and reorganization costs incurred	$ 3,718
Total restructuring and reorganization costs to be incurred	2,014
Total restructuring and reorganization costs incurred and to be incurred	5,732
One-time termination benefits
Restructuring Cost And Reserve [Line Items]
Total restructuring and reorganization costs incurred	3,379
Total restructuring and reorganization costs to be incurred	2,014
Total restructuring and reorganization costs incurred and to be incurred	5,393
Professional And Other
Restructuring Cost And Reserve [Line Items]
Total restructuring and reorganization costs incurred	339
Total restructuring and reorganization costs incurred and to be incurred	$ 339

Business Acquisitions - Additio

Business Acquisitions - Additional Information (Details) - USD ($) $ in Millions	Feb. 08, 2018	Dec. 31, 2018
Falcon Global Holdings
Noncontrolling Interest, ownership percentage by parent	72.00%	72.00%
Falcon Global Holdings
Joint venture, total capital	$ 112.5
Joint venture, contribution from previous joint venture	43.3
Joint venture, contribution from noncontrolling interest	$ 18.8

Business Acquisitions - Schedul

Business Acquisitions - Schedule of Allocation of Purchase Price for Company's Acquisitions (Details) $ in Thousands	Dec. 31, 2018USD ($)
Business Combinations [Abstract]
Other current assets	$ 211
Property and Equipment	140,257
Long-Term Debt	(106,640)
Minority Interest	(18,828)
Purchase price	$ 15,000	[1]
[1]	The Company did not have any acquisitions requiring purchase price allocation for the year ended December 31, 2019. Purchase price in 2018 was used to pay MOI’s debtor-in-possession obligations.

Equipment Acquisitions and Di_3

Equipment Acquisitions and Dispositions - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019USD ($)Vessel	Dec. 31, 2019GBP (£)Vessel	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Property Plant And Equipment [Line Items]
Capital expenditures and payments on equipment	$ 55,500,000		$ 51,600,000	$ 69,000,000
Gain (loss) on disposition of property, plant and equipment			5,700,000	3,900,000
Proceeds from sale of business	56,183,000		20,140,000	10,701,000
Net book value	692,360,000		744,102,000
Proceeds from deposits			100,000
Proceeds from sale of property, plant, and equipment, including deposits			17,400,000	10,900,000
Proceeds from sale of property, plant, and equipment, excluding deposits for future vessel sales			17,300,000
Increase (Decrease) in contract with customer, liability			$ 4,400,000	$ 100,000
Vessel Under Construction
Property Plant And Equipment [Line Items]
Gain (loss) on disposition of property, plant and equipment	6,600,000
Proceeds from sale of business	$ 55,100,000
Number of equipment sold | Vessel	1	1
Proceeds from property, plant, and equipment, including deposits and gain on sale	$ 59,400,000
Proceeds from deposits	$ 4,300,000
Anchor Handling Towing Supply
Property Plant And Equipment [Line Items]
Number of equipment sold | Vessel	5	5
Specialty Vessel
Property Plant And Equipment [Line Items]
Number of equipment sold | Vessel	1	1
Fast Support Vessels
Property Plant And Equipment [Line Items]
Number of equipment sold | Vessel	7	7
Anchor Handling Towing Supply Vessel and Other Equipment
Property Plant And Equipment [Line Items]
Number of equipment sold | Vessel	1	1
Liftboats
Property Plant And Equipment [Line Items]
Number of equipment sold | Vessel	3	3
Crew Transfer Vessels
Property Plant And Equipment [Line Items]
Number of equipment sold | Vessel	1	1
Platform Supply Vessels
Property Plant And Equipment [Line Items]
Number of equipment sold | Vessel	5	5
ERRV Fleet Business
Property Plant And Equipment [Line Items]
Gain (loss) on disposition of property, plant and equipment	$ (9,100,000)
Proceeds from sale of business	27,390,000
Net book value	23,400,000
Additional consideration	$ 5,200,000	£ 4,000,000
ERRV Fleet Business | Vessels
Property Plant And Equipment [Line Items]
Number of equipment sold | Vessel	18	18

Equipment Acquisitions and Di_4

Equipment Acquisitions and Dispositions - Schedule of Vessel Acquired and Disposed (Details)		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Property Plant And Equipment [Line Items]
Acquired		6	[1]	8		11
Removed from service		14	[2]	13	[3]	3	[4]
Fast Support Vessels
Property Plant And Equipment [Line Items]
Acquired		2	[1]			6
Removed from service		5	[2]	9	[3]
Offshore Support Vessels, Supply
Property Plant And Equipment [Line Items]
Acquired		2	[1]			5
Removed from service		5	[2]			1	[4]
Offshore Support Vessels, Liftboats
Property Plant And Equipment [Line Items]
Acquired				6
Removed from service		3	[2]	2	[3]	2	[4]
Crew Transfer Vessels
Property Plant And Equipment [Line Items]
Acquired		2	[1]	2
Removed from service	[3]			1
Anchor Handling Towing Supply
Property Plant And Equipment [Line Items]
Removed from service		1	[2]	1	[3]
[1]	Excludes three FSVs purchased from managed entities, one crew transfer vessel sold upon completion and one ERRV purchased from a joint venture.
[2]	Excludes the sale of (i) 18 ERRV vessels from the sale of the Company North Sea Standby Safety business, (ii) one crew transfer vessel to the joint venture FRS Windcat Offshore Logistics, (iii) one FSV to the joint venture OVH, (iv) one FSV to a third party with the Company continuing to manage the vessel, (v) one ERRV from discontinued operations and (vi) six vessels that were previously removed from service (five AHTS vessels and one specialty vessel).
[3]	Excludes three ERRVs from discontinued operations
[4]	Excludes one ERRV from discontinued operations.

Equipment Acquisitions and Di_5

Equipment Acquisitions and Dispositions - Schedule of Vessel Acquired and Disposed (Parenthetical) (Details)	12 Months Ended
	Dec. 31, 2019Vessel	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Number of equipment removed from service excludes from major equipment dispositions	6	3	1
Fast Support Vessels
Property Plant And Equipment [Line Items]
Number of equipment acquired excludes from deliveries of offshore support vessels	3
Number of equipment removed from service excludes from major equipment dispositions	1
Fast Support Vessels | Offshore Vessel Holdings
Property Plant And Equipment [Line Items]
Number of equipment removed from service excludes from major equipment dispositions	1
ERRV
Property Plant And Equipment [Line Items]
Number of equipment acquired excludes from deliveries of offshore support vessels	1
Number of equipment removed from service excludes from major equipment dispositions	18
Crew Transfer Vessels
Property Plant And Equipment [Line Items]
Number of equipment sold upon completion	1
Crew Transfer Vessels | Windcat Offshore Logistics
Property Plant And Equipment [Line Items]
Number of equipment removed from service excludes from major equipment dispositions	1
Anchor Handling Towing Supply
Property Plant And Equipment [Line Items]
Number of equipment removed from service excludes from major equipment dispositions	5
ERRV from Discontinued Operations
Property Plant And Equipment [Line Items]
Number of equipment removed from service excludes from major equipment dispositions	1

Investments, at Equity, and A_3

Investments, at Equity, and Advances to 50% or Less Owned Companies - Schedule of Equity Investments (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 20, 2018
Schedule Of Investments [Line Items]
Ownership percentage					49.00%
Investments at equity		$ 105,221	$ 121,773
Minimum
Schedule Of Investments [Line Items]
Ownership percentage		20.00%
Maximum
Schedule Of Investments [Line Items]
Ownership percentage		50.00%
MexMar
Schedule Of Investments [Line Items]
Ownership percentage		49.00%
Investments at equity		$ 54,249	53,840
SeaCosco Offshore LLC
Schedule Of Investments [Line Items]
Ownership percentage		50.00%
Investments at equity		$ 23,926	28,002
OSV Partners
Schedule Of Investments [Line Items]
Ownership percentage		30.40%
Investments at equity		$ 10,669	11,087
SEACOR Marlin LLC
Schedule Of Investments [Line Items]
Ownership percentage		49.00%
Investments at equity		$ 7,929	7,579
MEXMAR Offshore
Schedule Of Investments [Line Items]
Ownership percentage	[1]	49.00%
Investments at equity	[1]		4,900
Offshore Vessel Holdings
Schedule Of Investments [Line Items]
Ownership percentage		49.00%
Investments at equity		$ 4,052	4,900
Dynamic Offshore
Schedule Of Investments [Line Items]
Ownership percentage		19.00%
Investments at equity		$ 0	2,263
Nautical Power
Schedule Of Investments [Line Items]
Ownership percentage		50.00%
Other Offshore Marine Services Joint Ventures
Schedule Of Investments [Line Items]
Investments at equity		$ 4,396	9,202
Other Offshore Marine Services Joint Ventures | Minimum
Schedule Of Investments [Line Items]
Ownership percentage		20.00%
Other Offshore Marine Services Joint Ventures | Maximum
Schedule Of Investments [Line Items]
Ownership percentage		50.00%
All Other Excluding MexMar, Falcon Global, Sea-Cat Crewzer and Sea-Cat Crewzer II
Schedule Of Investments [Line Items]
Current assets		$ 108,238	99,400
Noncurrent assets		618,745	567,628
Current liabilities		106,742	59,912
Noncurrent liabilities		338,836	325,700
Operating Revenues		142,327	109,636	$ 147,360
Operating and administrative		119,767	77,952	78,025
Depreciation		28,800	26,443	30,499
Costs and expenses		148,567	104,395	108,524
Loss on Asset Dispositions and Impairments, Net		(166)	(89)
Operating Income		(6,406)	5,152	38,836
Net (Loss) Income		$ (36,341)	$ (13,945)	$ 13,189
[1]	This joint venture holds the investment in UP Offshore

Investments, at Equity, and A_4

Investments, at Equity, and Advances to 50% or Less Owned Companies - Additional Information (Details)	Dec. 18, 2019USD ($)	May 31, 2019USD ($)Vessel	Dec. 28, 2018USD ($)	Dec. 20, 2018USD ($)	Sep. 28, 2018USD ($)Vessel	Sep. 13, 2018USD ($)	Jan. 17, 2018USD ($)Vessel	Apr. 28, 2017USD ($)Catamaran	Sep. 30, 2018USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2019USD ($)VesselEquipment	Dec. 31, 2018USD ($)VesselLiftboat	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Feb. 08, 2018
Schedule Of Investments [Line Items]
Consolidated retained earnings											$ 16,100,000	$ 28,500,000
Payments to acquire property, plant, and equipment, total											55,456,000	51,578,000	$ 68,983,000
Contributed capital				$ 10,000,000
Equity method investment, ownership percentage				49.00%
Sale of subsidiary to joint venture												8,017,000
Equity method investment, other than temporary impairment											0	1,200,000	8,800,000
Income (loss) from equity method investments											(14,304,000)	(3,552,000)	3,851,000
Equity method investments											105,221,000	121,773,000
Principal payments on notes due from equity investees											22,000	116,000
Asset impairment charges, total											$ 12,000,000	14,600,000	27,500,000
Maximum
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage											50.00%
Minimum
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage											20.00%
MEXICO
Schedule Of Investments [Line Items]
Number of vessels owned | Vessel											3
Mexmar Offshore International
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage				49.00%
Noncontrolling interest, ownership percentage by noncontrolling owners				51.00%
Number of vessels owned | Vessel											13
Mexmar Offshore International | BRAZIL
Schedule Of Investments [Line Items]
Number of vessels owned | Vessel											10
Mexmar Offshore International | MEXICO
Schedule Of Investments [Line Items]
Number of vessels owned | Vessel											2
Offshore Vessel Holdings
Schedule Of Investments [Line Items]
Contributed capital											$ 10,000,000
Noncontrolling interest, ownership percentage by noncontrolling owners			51.00%
Noncontrolling Interest, ownership percentage by parent			49.00%
Payments to acquire interest in joint venture			$ 4,900,000
Financing agreement											$ 2,400,000
Offshore Support Vessels, Supply
Schedule Of Investments [Line Items]
Number of vessels owned | Vessel											1
Offshore Support Vessels, Supply | Offshore Vessel Holdings
Schedule Of Investments [Line Items]
Number of equipment operated | Equipment											3
Jack up Drillings [Member] | Offshore Vessel Holdings
Schedule Of Investments [Line Items]
Number of equipment operated | Equipment											2
F S V Offshore Support Vessels | Offshore Vessel Holdings
Schedule Of Investments [Line Items]
Number of equipment operated | Equipment											1
MexMar
Schedule Of Investments [Line Items]
Capital distributions from equity investees						$ 9,800,000					$ 0	9,800,000
Revenue from related parties											$ 300,000	300,000	300,000
Equity method investment, ownership percentage											49.00%
Number of vessels owned | Vessel											16
Equity method investments											$ 54,249,000	53,840,000
MexMar | Offshore Support Vessels
Schedule Of Investments [Line Items]
Number of equipment operated | Vessel											16
SeaCosco Offshore LLC
Schedule Of Investments [Line Items]
Number of equipment operated | Vessel							8
Payments to acquire property, plant, and equipment, total							$ 163,300,000
Contributed capital											$ 2,000,000	29,600,000
Equity method investment, ownership percentage											50.00%
Number of vessels owned | Vessel											1
Equity method investments											$ 23,926,000	$ 28,002,000
SeaCosco Offshore LLC | MOU
Schedule Of Investments [Line Items]
Agreement standstill date		Aug. 31, 2019
Loans receivable, interest rate		15.00%
Shareholder loans in respect of working capital		$ 13,000,000
Interest income recognized on shareholder loans in respect of working capital		600,000
Advanced contributed capital		$ 2,100,000
SeaCosco Offshore LLC | SEACOR Offshore Asia
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage							50.00%
SeaCosco Offshore LLC | CSFT and CSIHK
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage							50.00%
SeaCosco Offshore LLC | CSFT and CSIHK | MOU
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage		50.00%
SeaCosco Offshore LLC | Platform Supply Vessels
Schedule Of Investments [Line Items]
Number of vessels delivered to the company | Vessel											5	2
SeaCosco Offshore LLC | Platform Supply Vessels | MOU
Schedule Of Investments [Line Items]
Number of vessels acquired | Vessel		2
OSV Partners
Schedule Of Investments [Line Items]
Revenue from related parties											$ 0	$ 600,000	600,000
Contributed capital					$ 5,000,000								2,300,000
Equity method investment, ownership percentage											30.40%
Investment in affiliates, amount of preferred equity offering participated					5,000,000
Payments to acquire interest in subsidiaries and affiliates, total	$ 1,100,000				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											$ 10,669,000	11,087,000
OSV Partners | General Partner
Schedule Of Investments [Line Items]
Contributed capital													6,000,000
Equity method investment, ownership percentage											38.60%
OSV Partners | Offshore Support Vessels
Schedule Of Investments [Line Items]
Number of equipment operated | Vessel					5
SEACOR Marlin LLC
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage											49.00%
Equity method investment, ownership, percent sold						51.00%
Sale of subsidiary to joint venture						$ 8,000,000
Gain (loss) on disposition of business						$ 400,000
Equity method investments											$ 7,929,000	7,579,000
Dynamic Offshore
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage											19.00%
Equity method investment, other than temporary impairment													8,300,000
Income (loss) from equity method investments											$ (2,300,000)	(2,000,000)
Equity method investments											$ 0	$ 2,263,000
Nautical Power
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage											50.00%
Sale of subsidiary to joint venture									$ 6,400,000
Falcon Global
Schedule Of Investments [Line Items]
Contributed capital										$ 400,000
Equity method investment, ownership percentage															100.00%
Payments for advance to affiliate										$ 2,000,000
Business acquisition, percentage of voting interests acquired										100.00%
Falcon Global | Liftboats
Schedule Of Investments [Line Items]
Number of equipment operated | Liftboat												2
Sea-Cat Crewzer II
Schedule Of Investments [Line Items]
Number of equipment operated | Catamaran								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
Schedule Of Investments [Line Items]
Number of equipment operated | Catamaran								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
Schedule Of Investments [Line Items]
Number of equipment operated | Vessel											5
Capital distributions from equity investees											$ 2,100,000		2,600,000
Revenue from related parties													300,000	$ 700,000
Contributed capital													800,000
Equity method investment, other than temporary impairment												$ 1,200,000	500,000
Equity method investments											4,396,000	$ 9,202,000
Return of capital equity method investment											500,000
Principal payments on notes due from equity investees													$ 200,000
Other Offshore Marine Services Joint Ventures | Maximum
Schedule Of Investments [Line Items]
Revenue from related parties											$ 100,000
Equity method investment, ownership percentage											50.00%
Other Offshore Marine Services Joint Ventures | Minimum
Schedule Of Investments [Line Items]
Equity method investment, ownership percentage											20.00%

Construction Reserve Funds - Ad

Construction Reserve Funds - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019ExtensionPeriod
Restricted Cash And Investments [Abstract]
Construction reserve funds commitment period	3 years
Number of extension period	2
Construction reserve funds extension period	1 year

Construction Reserve Funds - Sc

Construction Reserve Funds - Schedule of Construction Reserve Fund Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Cash And Investments [Abstract]
Withdrawals	$ (15,168)	$ (17,300)	$ (39,163)
Deposits			6,315
Construction reserve fund, net	$ (15,168)	$ (17,300)	$ (32,848)

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	Jan. 01, 2019USD ($)	Dec. 31, 2019USD ($)Vessel	Dec. 31, 2018USD ($)
Lessee Lease Description [Line Items]
Operating Lease, Right-of-Use Asset		$ 17,313
Operating Lease, Liability		24,921
Operating Lease, Impairment Loss		$ 5,300	$ 6,800
Number of Operating Leases Impaired		1	3
Anchor Handling Towing Supply
Lessee Lease Description [Line Items]
Number of operating leases on equipment | Vessel		3
Liftboats
Lessee Lease Description [Line Items]
Number of operating leases on equipment | Vessel		2
Fast Support Vessels
Lessee Lease Description [Line Items]
Number of operating leases on equipment | Vessel		1
Vessels | Minimum
Lessee Lease Description [Line Items]
Operating lease, lease terms (in duration)		11 years
Vessels | Maximum
Lessee Lease Description [Line Items]
Operating lease, lease terms (in duration)		23 months
Other Equipment | Minimum
Lessee Lease Description [Line Items]
Operating lease, lease terms (in duration)		1 month
Other Equipment | Maximum
Lessee Lease Description [Line Items]
Operating lease, lease terms (in duration)		324 months
Accounting Standards Update 2016-02
Lessee Lease Description [Line Items]
Operating Lease, Right-of-Use Asset	$ 33,700
Operating Lease, Liability	31,900
Accounting Standards Update 2016-02 | Change in Accounting Principle for Equipment, Office and Land Leases
Lessee Lease Description [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax, Total	1,700
Accounting Standards Update 2016-02 | Change in Accounting Principle for Unamortized Deferred Gains
Lessee Lease Description [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax, Total	8,700
Cumulative effect on retained earnings, Before tax	11,000
Cumulative effect on retained earnings, Tax	$ 2,300

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Payments For Operating Leases (Details) $ in Thousands	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 15,355
2021	7,128
2022	668
2023	621
2024	696
Years subsequent to 2024	4,437
Operating lease payments due	28,905
Interest component	(3,984)
Total operating leases	24,921
Current portion of operating lease liabilities	15,099
Long-Term Operating Lease Liabilities	$ 9,822

Leases - Summary of Components

Leases - Summary of Components of Leases Expense (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Leases [Abstract]
Operating lease expense	$ 13,639
Short-term lease expense (lease duration of twelve months or less at lease commencement)	2,519
Total Lease expense	$ 16,158

Leases - Summary of Other Infor

Leases - Summary of Other Information Related to Operating Leases (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ 19,339
Right-of-use assets obtained for operating lease liabilities	$ 35,246
Weighted average remaining lease term, in years	4 years 8 months 12 days
Weighted average discount rate	4.10%

Long Term Debt - Schedule of Lo

Long Term Debt - Schedule of Long-term Debt Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 429,823	$ 442,972
Portion due within one year	(17,802)	(16,812)
Debt discount	(26,343)	(32,005)
Issue costs	(5,427)	(6,301)
Long-term debt	380,251	387,854
Convertible Senior Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	125,000	125,000
SEACOR Marine Foreign Holdings Loan Facility
Debt Instrument [Line Items]
Long-term Debt, Gross	113,750	126,750
Falcon Global USA Term Loan Facility
Debt Instrument [Line Items]
Long-term Debt, Gross	102,349	109,099
Sea-Cat Crewzer III Term Loan Facility
Debt Instrument [Line Items]
Long-term Debt, Gross	24,128	25,989
Windcat Workboats Facilities
Debt Instrument [Line Items]
Long-term Debt, Gross	24,730	24,850
Falcon Global USA Revolver
Debt Instrument [Line Items]
Long-term Debt, Gross	15,000	15,000
SEACOR 88/888 Term Loan
Debt Instrument [Line Items]
Long-term Debt, Gross	11,000	11,000
SEACOR Alps
Debt Instrument [Line Items]
Long-term Debt, Gross	10,534
BNDES Equipment Construction Finance Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 3,332	$ 5,284

Long Term Debt - Schedule of _2

Long Term Debt - Schedule of Long-term Debt Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
2020	$ 17,802
2021	51,789
2022	26,007
2023	231,674
2024	90,800
Years subsequent to 2024	11,752
Long-term Debt, Gross	$ 429,823	$ 442,972

Long Term Debt - Additional Inf

Long Term Debt - Additional Information (Details)	Dec. 18, 2019USD ($)	Dec. 20, 2018USD ($)	Sep. 28, 2018USD ($)Vessel	Sep. 26, 2018USD ($)	Jul. 05, 2018USD ($)	May 02, 2018USD ($)$ / sharesshares	Feb. 08, 2018USD ($)	Nov. 03, 2017USD ($)	Apr. 28, 2017Catamaran	Apr. 30, 2018USD ($)$ / sharesshares	Sep. 30, 2019	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)EUR (€)Tranche	Dec. 31, 2018USD ($)	Dec. 31, 2018EUR (€)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2016EUR (€)	Oct. 31, 2018USD ($)	Mar. 31, 2017USD ($)	May 24, 2016EUR (€)	Apr. 21, 2016EUR (€)	Dec. 01, 2015USD ($)$ / shares	Aug. 03, 2015USD ($)
Debt Instrument [Line Items]
Debt instrument, increase (decrease), net, total				$ 30,100,000										$ 1,000,000
Loss on extinguishment of debt														638,000
Contributed capital		$ 10,000,000
Debt instrument unamortized discount													$ 26,343,000	32,005,000
Repayments of long-term debt, total													23,974,000	49,405,000		$ 11,926,000
Long-Term Debt														$ 106,640,000
Equity method investment, ownership percentage		49.00%
Long-term Debt Obligation
Debt Instrument [Line Items]
Letters of credit outstanding, amount													$ 500,000
Minimum
Debt Instrument [Line Items]
Equity method investment, ownership percentage													20.00%
Maximum
Debt Instrument [Line Items]
Equity method investment, ownership percentage													50.00%
Falcon Global Holdings
Debt Instrument [Line Items]
Noncontrolling Interest, ownership percentage by parent							72.00%							72.00%
Falcon Global USA LLC
Debt Instrument [Line Items]
Payments for debtor in possession obligations							$ 15,000,000
Carlyle Group
Debt Instrument [Line Items]
Convertible debt, total																							$ 175,000,000
Carlyle Group | Maximum
Debt Instrument [Line Items]
Convertible debt, total												$ 50,000,000				50,000,000
Convertible Senior Notes Converted to Warrants | Carlyle Group
Debt Instrument [Line Items]
Debt instrument, convertible, conversion ratio						37.73				37.73
Debt instrument, face amount						$ 1,000				$ 1,000
Class of warrant or right, exercise price of warrants or rights | $ / shares						$ 0.01				$ 0.01
Debt conversion, original debt, amount						$ 50,000,000				$ 50,000,000
Debt conversion, converted instrument, shares issued | shares						1,886,792				1,900,000
Debt instrument, convertible, conversion price | $ / shares						$ 26.50				$ 26.50
Conversion Revolving Credit Facility from Windcat Workboats
Debt Instrument [Line Items]
Debt conversion, original debt, amount | €															€ 6,000,000
Carlyle Warrants
Debt Instrument [Line Items]
Class of warrant or right, exercise price of warrants or rights | $ / shares																							$ 0.01
Warrants and rights outstanding, term						25 years
OSV Partners
Debt Instrument [Line Items]
Contributed capital			$ 5,000,000													2,300,000
Investment in affiliates, amount of preferred equity offering participated			5,000,000
Payments to acquire interest in subsidiaries and affiliates, total	$ 1,100,000		1,100,000
Commitment to invest additional funds if call by general partner			1,100,000
Payments to acquire loans receivable			$ 2,100,000
Revenue from related parties													$ 0	$ 600,000		600,000
Equity method investment, ownership percentage													30.40%
OSV Partners | General Partner
Debt Instrument [Line Items]
Contributed capital																$ 6,000,000
Equity method investment, ownership percentage													38.60%
OSV Partners | Offshore Support Vessels
Debt Instrument [Line Items]
Number of equipment operated | Vessel			5
Falcon Global
Debt Instrument [Line Items]
Business acquisition, percentage of voting interests acquired																				100.00%
Sea-Cat Crewzer II
Debt Instrument [Line Items]
Number of equipment operated | Catamaran									2
Repayments of long-term debt, total			$ 19,100,000											1,800,000
Business acquisition, percentage of voting interests acquired									100.00%
Equity method investment, ownership percentage									50.00%
Sea-Cat Crewzer
Debt Instrument [Line Items]
Debt instrument, interest rate												1.52%				1.52%
Debt instrument, interest rate, effective percentage												5.64%				5.64%
Number of equipment operated | Catamaran									2
Repayments of long-term debt, total			16,900,000											$ 1,600,000		$ 1,100,000
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
Sea-Cat Crewzer | Minimum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate																2.10%
Sea-Cat Crewzer | Maximum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate																2.75%
SEACOR Alps
Debt Instrument [Line Items]
Debt instrument, interest rate											5.00%
Percentage of amount of loan financed											70.00%
Debt instrument, maturity period											2023
Loan Facility With DNB Bank ASA
Debt Instrument [Line Items]
Debt instrument, maturity period				2023
Line of credit facility, maximum borrowing capacity				$ 130,000
Debt instrument, interest rate, effective percentage				5.875%
Debt instrument, periodic payment, principal				$ 3,300,000
Loan Facility With DNB Bank ASA | Interest Rate Swap
Debt Instrument [Line Items]
Derivative, notional amount																			$ 65,000,000
Other DNB Credit Facilities
Debt Instrument [Line Items]
Repayments of lines of credit				101,300,000
Long-term debt, total				99,900,000
Interest payable				1,400,000
Loss on extinguishment of debt				$ 600,000
Convertible Senior Notes 3.75%
Debt Instrument [Line Items]
Debt instrument, interest rate						4.25%				4.25%													3.75%
Convertible debt, total						$ 125,000,000				$ 125,000,000													$ 175,000,000
Debt instrument, convertible, conversion ratio														23.26	23.26
Debt instrument, face amount														$ 1,000
Three Point Seven Five Percentage Convertible Notes
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage														7.95%
Embedded derivative, fair value of embedded derivative liability																							$ 27,300,000
FGUSA Credit Facility
Debt Instrument [Line Items]
Debt agreement maximum borrowing capacity							131,100,000
Debt instrument unamortized discount							10,000,000
FGUSA Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity							15,000,000
Debt instrument, interest rate, effective percentage													6.3125%
Debt instrument unamortized discount							500,000
Proceeds from lines of credit, total														$ 15,000,000
FGUSA Credit Facility | Term Loan
Debt Instrument [Line Items]
Long-term debt, total							116,100,000
Debt instrument, periodic payment, principal														7,000,000
Debt instrument unamortized discount							$ 9,500,000
Sea-Cat Crewzer III
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage												2.76%				2.76%
Debt instrument, face amount | €																						€ 27,600,000
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 Facilities
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity | €																					€ 25,000,000
Proceeds from lines of credit, total																	23,500,000	€ 21,000,000
Debt issuance costs, gross																	600,000
Repayments of long-term debt, total																	$ 22,900,000
Line of credit facility, collateral description														Windcat Workboats entered into a €25.0 million revolving credit facility secured by 38 of the Company’s CTV fleet.	Windcat Workboats entered into a €25.0 million revolving credit facility secured by 38 of the Company’s CTV fleet.
Debt instrument, maturity year														2021	2021
Windcat Workboats Facilities | Minimum
Debt Instrument [Line Items]
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 Facilities | Maximum
Debt Instrument [Line Items]
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
Debt Instrument [Line Items]
Repayments of long-term debt, total														$ 7,500,000
Pound Sterling Debt
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt, total														8,500,000
Term Loan to Acquire Two Vessels
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage					5.5625%
Debt instrument, face amount					$ 11,000,000
Debt instrument, maturity year													2023
Claims recoverable amount under borrowings					$ 5,500,000
Claims recoverable under borrowings percentage of obligations outstanding					50.00%
Term Loan to Acquire Two Vessels | Interest Rate Swap
Debt Instrument [Line Items]
Derivative, notional amount																			$ 5,500,000
BNDES Equipment Construction Finance Notes
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage													4.00%
Repayments of long-term debt, total													$ 2,000,000	2,000,000		$ 2,000,000
Debt instrument maturity date description													July through October 2021
Falcon Global
Debt Instrument [Line Items]
Debt issuance costs, gross																				$ 1,000,000
Repayments of long-term debt, total			$ 51,900,000									$ 4,400,000		$ 3,000,000
Number of foreign-flag liftboats to be constructed under term loan | €													2
Number of tranches | Tranche													2
Debt instrument repayment term													5 years
Debt instrument, maturity date													Jun. 30, 2022
Payments of debt issuance costs								$ 200,000
Long-Term Debt																				$ 58,300,000
Tranche A | Falcon Global
Debt Instrument [Line Items]
Debt instrument, face amount																								$ 62,500,000
Tranche B | Falcon Global
Debt Instrument [Line Items]
Debt instrument, face amount																								$ 18,000,000
Sea-Cat Crewzer II
Debt Instrument [Line Items]
Debt instrument, interest rate												1.52%				1.52%
Debt instrument, interest rate, effective percentage												5.64%				5.64%
Repayments of long-term debt, total																$ 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 | Minimum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate																2.10%
Sea-Cat Crewzer II | Maximum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate																2.75%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Effective income tax rate reconciliation, at federal statutory Income tax rate, percent	21.00%	21.00%	35.00%
Income tax benefit and equity in earnings (losses)	(50.00%)
Increase (decrease) in transition tax liability	$ 2,300		$ 3,400,000
Current income tax expense (benefit), nonqualified withdrawal of funds from capital construction fund		$ 1,400,000
Income tax expense (benefit), continuing operations, adjustment of deferred tax (asset) liability			$ (3,900,000)
Effective income tax rate reconciliation, percent, total	9.60%	14.30%	63.20%
Exclusion of foreign subsidiaries with accumulated losses and withholding tax	7.20%	9.50%	3.10%
Noncontrolling interests	1.80%	(1.50%)	1.70%
Tax Cuts and Jobs Act of 2017, income tax expense (benefit)			$ 43,700,000
Interest expense suspended	$ 6,600,000	$ 3,600,000
Interest expense carryforward		10,200,000
Interest expense suspended, limitation percentage	30.00%
Operating loss carryforwards, percentage of taxable income, utilization limitation	80.00%
Operating loss carryforwards, total	$ 42,200,000	$ 94,500,000
Operating loss carryforwards, expiration period		20 years
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Operating loss carryforwards, valuation allowance, total	$ 1,300,000

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income before Income Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Income before income tax expense (benefit) and equity in earnings of 50% or less owned companies	$ (82,836)	$ (93,224)	$ (117,790)
United States
Income Taxes [Line Items]
Income before income tax expense (benefit) and equity in earnings of 50% or less owned companies	(71,833)	(72,540)	(90,696)
Foreign
Income Taxes [Line Items]
Income before income tax expense (benefit) and equity in earnings of 50% or less owned companies	(22,025)	(29,466)	(45,879)
Eliminations
Income Taxes [Line Items]
Income before income tax expense (benefit) and equity in earnings of 50% or less owned companies	$ 11,022	$ 8,782	$ 18,785

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal, current	$ (6)	$ 5,987	$ (16,705)
State, current	(78)	3	(42)
Foreign, current	5,039	3,393	3,343
Current income tax expense	4,955	9,383	(13,404)
Federal, deferred	(12,594)	(21,466)	(60,750)
State, deferred	(224)	(1,404)	(172)
Foreign, deferred	(49)	133	(84)
Deferred income tax benefit	(12,867)	(22,737)	(61,006)
Income Tax Expense (Benefit)	$ (7,912)	$ (13,354)	$ (74,410)

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory rate	(21.00%)	(21.00%)	(35.00%)
U.S. federal income tax law changes			(37.30%)
SEACOR Holdings share awards to Company personnel		0.20%	2.30%
Non-deductible expenses			1.80%
Exclusion of foreign subsidiaries with accumulated losses and withholding tax	7.20%	9.50%	3.10%
Noncontrolling interests	1.80%	(1.50%)	1.70%
State taxes	(0.30%)	(1.50%)	(0.20%)
Return to provision	2.90%	(0.50%)	0.40%
Other	(0.20%)	0.50%
Effective Tax Rate	(9.60%)	(14.30%)	(63.20%)

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax liabilities:
Property and equipment	$ 63,827	$ 65,880
Investments in 50% or Less Owned Companies	3,039	3,040
Other	10,953	7,792
Total deferred tax liabilities	77,819	76,712
Deferred tax assets:
Federal Net Operating Loss Carryforwards	28,664	20,974
Other	16,561	11,677
Total deferred tax assets	45,225	32,651
Valuation Allowance	(1,311)	(624)
Total deferred tax assets	43,914	32,027
Net deferred tax liabilities	$ 33,905	$ 44,685

Derivative Instruments and He_3

Derivative Instruments and Hedging Strategies - Schedule of Fair Value of Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Designated as Hedging Instrument | Cash Flow Hedging
Derivative [Line Items]
Derivative Liability	$ 3,009	$ 1,659
Designated as Hedging Instrument | Interest Rate Swap | Cash Flow Hedging | Current Liabilities
Derivative [Line Items]
Derivative Liability	3,009	1,659
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liability	8,214	6,935
Not Designated as Hedging Instrument | Non-current Liabilities
Derivative [Line Items]
Embedded derivative, fair value of embedded derivative liability	$ 5,205	$ 5,276

Derivative Instruments and He_4

Derivative Instruments and Hedging Strategies - Additional Information (Details) $ in Thousands, € in Millions	12 Months Ended
	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2019EUR (€)
Derivative [Line Items]
Other comprehensive income (loss), unrealized gain (loss) on derivatives arising during period, before tax	$ (1,901)	$ (1,939)	$ 214
Derivative, Fair Value, Net, Total	8,200
Interest Rate Swap
Derivative [Line Items]
Other comprehensive income (loss), unrealized gain (loss) on derivatives arising during period, before tax	$ (1,901)	(1,939)	214
Interest Rate Swap | OSV Partners
Derivative [Line Items]
Derivative, number of instruments held, total	2			2
Derivative, notional amount	$ 22,800
Interest Rate Swap | OSV Partners | Minimum
Derivative [Line Items]
Derivative, fixed interest rate	1.89%			1.89%
Interest Rate Swap | OSV Partners | Maximum
Derivative [Line Items]
Derivative, fixed interest rate	2.27%			2.27%
Cash Flow Hedging
Derivative [Line Items]
Other comprehensive income (loss), unrealized gain (loss) on derivatives arising during period, before tax	$ (1,300)	$ 1,600	(200)
Cash Flow Hedging | Interest Rate Swap | Designated as Hedging Instrument | Windcat Workboats Holdings Ltd
Derivative [Line Items]
Derivative, number of instruments held, total	2			2
Derivative, fixed interest rate	0.03%			0.03%
Derivative, notional amount	$ 16,800			€ 15
Cash Flow Hedging | Interest Rate Swap | Designated as Hedging Instrument | SEACOR 88/888
Derivative [Line Items]
Derivative, fixed interest rate	3.175%			3.175%
Derivative, notional amount	$ 5,500
Cash Flow Hedging | Interest Rate Swap | Designated as Hedging Instrument | MexMar
Derivative [Line Items]
Derivative, number of instruments held, total	5			5
Derivative, notional amount	$ 83,200
Cash Flow Hedging | Interest Rate Swap | Designated as Hedging Instrument | MexMar | Minimum
Derivative [Line Items]
Derivative, fixed interest rate	1.71%			1.71%
Cash Flow Hedging | Interest Rate Swap | Designated as Hedging Instrument | MexMar | Maximum
Derivative [Line Items]
Derivative, fixed interest rate	2.10%			2.10%
Cash Flow Hedging | 3.32% Interest Rate Swap Agreement | Designated as Hedging Instrument | SEACOR Marine Foreign Holdings
Derivative [Line Items]
Derivative, fixed interest rate	3.32%			3.32%
Derivative, notional amount	$ 8,800
Cash Flow Hedging | 3.195% Interest Rate Swap Agreement | Designated as Hedging Instrument | SEACOR Marine Foreign Holdings
Derivative [Line Items]
Derivative, fixed interest rate	3.195%			3.195%
Derivative, notional amount	$ 48,600
Construction in Progress | Fair Value Hedging
Derivative [Line Items]
Change in unrealized gain (loss) on hedged item in fair value hedge			$ 100

Derivative Instruments and He_5

Derivative Instruments and Hedging Strategies - Effect of Derivative Instruments on Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other comprehensive income (loss), unrealized gain (loss) on derivatives arising during period, before tax	$ (1,901)	$ (1,939)	$ 214
Interest Rate Swap
Other comprehensive income (loss), unrealized gain (loss) on derivatives arising during period, before tax	(1,901)	(1,939)	214
Joint Venture Interest Rate Swap
Other comprehensive income (loss), unrealized gain (loss) on derivatives arising during period, before tax	(645)	(76)	389
Interest Expense
Reclassification of derivative gains (losses) on cash flow hedges	$ 552	$ 31	$ 118

Derivative Instruments and He_6

Derivative Instruments and Hedging Strategies - Gains (Losses) on Derivative Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gains (losses) on derivative instruments	$ 71	$ 2,854	$ 20,256
Embedded Derivative Financial Instruments
Gains (losses) on derivative instruments	$ 71	1,556	20,422
Interest Rate Swap
Gains (losses) on derivative instruments		$ 1,298	46
Foreign Exchange Option
Gains (losses) on derivative instruments			$ (212)

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Fair Value, Inputs, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Construction reserve funds		$ 12,893	$ 28,221
Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments (included in other receivables)			419
Derivative Liability		3,009	1,659
Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Conversion Option Liability on Convertible Senior Notes	[1]	$ 5,205	$ 5,276
[1]	For the year ended December 31, 2019, the Company recognized a $0.1 million gain in the fair market valuation of the Convertible Senior Notes, as valued by an independent third-party

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis (Details) (Parenthetical) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Fair Value Disclosures [Abstract]
Derivative, gain (loss) on derivative, net, total	$ 0.1

Fair Value Measurements - Sch_3

Fair Value Measurements - Schedule of Estimated Fair Values of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Reported Value Measurement
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash	$ 87,047	$ 93,254
Investments, at cost, in 50% or less owned companies (included in other assets)	132	132
Long-term debt, including current portion	398,053	404,666
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash	87,047	93,254
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, including current portion	$ 380,815	$ 388,949

Fair Value Measurements - Sch_4

Fair Value Measurements - Schedule of Other Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Inputs, Level 2 | Anchor Handling Towing Supply
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Property and equipment	$ 520	$ 2,000
Fair Value, Inputs, Level 2 | Fast Support Vessels
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Property and equipment	$ 1,858
Fair Value, Inputs, Level 2 | Offshore Support Vessels, Specialty
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Property and equipment		4,500
Fair Value, Inputs, Level 3 | Liftboats
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Property and equipment		$ 134,775

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Impairment charges	$ 12	$ 14.6	$ 27.5

Warrants - Additional Informati

Warrants - Additional Information (Details) - USD ($)	Jun. 14, 2019	May 28, 2019	Jun. 08, 2018	May 31, 2018	May 02, 2018	Apr. 26, 2018	Apr. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Class Of Warrant Or Right [Line Items]
Stock issued during period, value, new issues								$ 6,596,000	$ 42,996,000
Class of warrant or right, exercised during period			38,857	250,693
Carlyle Group | Convertible Senior Notes Converted to Warrants
Class Of Warrant Or Right [Line Items]
Class of warrant or right, exercise price of warrants or rights					$ 0.01		$ 0.01
Debt conversion, original debt, amount					$ 50,000,000		$ 50,000,000
Warrants Issued in Private Placement
Class Of Warrant Or Right [Line Items]
Class of warrant or right, outstanding						2,168,586	2,168,586
Class of warrant or right, number of securities called by warrants or rights						674,164	674,164
Class of warrant or right, exercise price of warrants or rights						$ 0.01	$ 0.01
PIPE Warrants
Class Of Warrant Or Right [Line Items]
Class of warrant or right, exercise price of warrants or rights						$ 0.01
Warrants and rights outstanding, term						25 years
Exchange Warrants
Class Of Warrant Or Right [Line Items]
Class of warrant or right, outstanding								1,826,966	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	64,440	380,000	38,857	250,693
Number of shares withheld in an exercise to purchase warrants as payment for the exercise	49
Exchange Warrants | Carlyle Group
Class Of Warrant Or Right [Line Items]
Class of warrant or right, number of securities called by warrants or rights					1,886,292
Private Placement
Class Of Warrant Or Right [Line Items]
Stock issued during period, value, new issues						$ 56,855,000	$ 15,000,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) € in Millions, £ in Millions	Mar. 15, 2019USD ($)shares	Mar. 15, 2019GBP (£)shares	Mar. 15, 2019EUR (€)shares	Jan. 25, 2019USD ($)	Jan. 25, 2019GBP (£)	Jan. 09, 2019USD ($)Vesselshares	Jun. 08, 2018shares	May 31, 2018shares	May 02, 2018USD ($)	Apr. 26, 2018shares	Mar. 26, 2018USD ($)shares	Feb. 08, 2018USD ($)Vessel	Apr. 30, 2018USD ($)shares	Dec. 31, 2019USD ($)shares		Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Jan. 01, 2019USD ($)	Jan. 01, 2018USD ($)
Class Of Stock [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption																$ 10,416,000	$ (12,069,000)
Stock Issued During Period, Shares, New Issues | shares											103,213
Acquired														6	[1]	8	11
Common stock value														$ 219,000		$ 204,000
Number of liftboat vessels operated | Vessel												15
Debt discount														$ 26,343,000		32,005,000
Adjustment to stockholders equity due to unamortized debt discount												$ 400,000
Proceeds from issuance of private placement											$ 1,800,000
Class of warrant or right, exercised during period | shares							38,857	250,693
Common stock held in treasury in exchange for payment of warrants converted | shares														108
Carlyle Group | Convertible Senior Notes Converted to Warrants
Class Of Stock [Line Items]
Debt conversion, original debt, amount									$ 50,000,000				$ 50,000,000
FGUSA Credit Facility
Class Of Stock [Line Items]
Debt agreement maximum borrowing capacity												131,100,000
Debt discount												10,000,000
FGUSA Credit Facility | Revolving Credit Facility
Class Of Stock [Line Items]
Debt discount												500,000
FGUSA Credit Facility | Term Loan
Class Of Stock [Line Items]
Debt discount												$ 9,500,000
Montco Offshore, LLC
Class Of Stock [Line Items]
Number of liftboat vessels operated | Vessel												6
Falcon Global USA LLC
Class Of Stock [Line Items]
Payments for debtor in possession obligations												$ 15,000,000
Windcat Workboats Facilities | Seabulk Overseas
Class Of Stock [Line Items]
Business acquisition, percentage of voting interests acquired	6.25%	6.25%	6.25%	6.25%	6.25%									100.00%
Business combination, consideration transferred, total	$ 1,400,000	£ 1.2	€ 1.2	$ 2,000,000	£ 1.6
Business acquisition, exchange for consideration | shares	50,000	50,000	50,000
Private Placement
Class Of Stock [Line Items]
Stock Issued During Period, Shares, New Issues | shares						603,872				56,900,000			750,000
Acquired | Vessel						3
Common stock value						$ 7,800
Retained Earnings
Class Of Stock [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption																$ 10,416,000	$ (12,069,000)
Retained Earnings | Accounting Standards Update 2016-02
Class Of Stock [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption																		$ 10,400,000	$ (12,100)
[1]	Excludes three FSVs purchased from managed entities, one crew transfer vessel sold upon completion and one ERRV purchased from a joint venture.

Noncontrolling Interests in S_3

Noncontrolling Interests in Subsidiaries - Schedule of Noncontrolling Interests in the Company's Consolidated Subsidiaries (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Minority Interest [Line Items]
Noncontrolling interest	$ 21,432	$ 29,404
Falcon Global
Minority Interest [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	28.00%
Noncontrolling interest	$ 21,119	$ 26,989
Windcat Workboats
Minority Interest [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners		12.50%
Noncontrolling interest		$ 2,115
Other Noncontrolling Interests
Minority Interest [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	1.80%
Noncontrolling interest	$ 313	$ 300

Noncontrolling Interests in S_4

Noncontrolling Interests in Subsidiaries - Schedule of Noncontrolling Interests in the Company's Consolidated Subsidiaries (Parenthetical) (Details)	Dec. 31, 2018
Windcat Workboats
Minority Interest [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	12.50%

Noncontrolling Interests in S_5

Noncontrolling Interests in Subsidiaries - Additional Information (Details) - USD ($) $ in Thousands	Feb. 08, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 15, 2019	Jan. 25, 2019
Minority Interest [Line Items]
Net income (loss), including portion attributable to noncontrolling interest, total		$ (21,918)	$ (18,240)	$ (30,264)	$ (28,273)	$ (7,969)	$ (15,766)	$ (26,629)	$ (31,688)	$ (98,695)	$ (82,052)	$ (38,540)
Net income (loss) attributable to noncontrolling interest, total										(5,858)	$ (4,444)	$ (5,639)
Falcon Global Holdings
Minority Interest [Line Items]
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
Minority Interest [Line Items]
Noncontrolling interest, ownership percentage by parent	72.00%
Net income (loss), including portion attributable to noncontrolling interest, total										21,000
Net income (loss) attributable to noncontrolling interest, total										5,900
Net assets, ending balance		$ 77,200								$ 77,200
Windcat Workboats
Minority Interest [Line Items]
Noncontrolling interest, ownership percentage by parent						12.50%					12.50%
Net income (loss), including portion attributable to noncontrolling interest, total											$ (3,100)
Net income (loss) attributable to noncontrolling interest, total											(400)
Net assets, ending balance						$ 16,900					$ 16,900
Windcat Workboats | Seabulk Overseas
Minority Interest [Line Items]
Noncontrolling interest, ownership percentage by parent														87.00%
Business acquisition, percentage of voting interests acquired													6.25%	6.25%

Savings and Multi-employer Pe_2

Savings and Multi-employer Pension Plans - Additional Information (Details) $ in Thousands, € in Millions, £ in Millions	Jan. 01, 2019	Jun. 30, 2018USD ($)	Jun. 30, 2018EUR (€)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2014USD ($)	Nov. 07, 2018GBP (£)	Dec. 31, 2015USD ($)	Dec. 31, 2013USD ($)
Pension And Other Postretirement Benefits Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of employees' gross pay	1.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount				$ 300
Other Defined Contribution Plan
Pension And Other Postretirement Benefits Disclosure [Line Items]
Defined contribution plan, cost				300	$ 200	$ 200
United Kingdom Merchant Navy Officers Pension Fund | Foreign Pension Plan
Pension And Other Postretirement Benefits Disclosure [Line Items]
Pension and other postretirement benefits cost (reversal of cost), total							$ 19,400
Pension and other postretirement benefits invoice										$ 2,600
Pension and other post-retirement benefit plans, total funding deficit | £								£ 9
Liability, defined benefit pension plan, current				300
Liability, defined benefit pension plan, noncurrent				$ 700
Merchant Navy Ratings Pension Fund
Pension And Other Postretirement Benefits Disclosure [Line Items]
Multiemployer plan, contributions by employer		$ 1,190	€ 0.9
Merchant Navy Ratings Pension Fund | Foreign Pension Plan
Pension And Other Postretirement Benefits Disclosure [Line Items]
Pension and other post-retirement benefit plans, total funding deficit									$ 6,900

Share Based Compensation - Addi

Share Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Payments for distribution of restricted stock, spin-off			$ 2,700
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, total	$ 6,500	$ 6,800	$ 5,200
Share-based compensation arrangement by share-based payment award, options, outstanding, exercise price, ending balance	$ 14.85
Share-based compensation arrangement by share-based payment award, options, outstanding, number, ending balance	913,569	805,566	613,700
Share-based compensation arrangement by share-based payment award, options, outstanding, weighted average remaining contractual term	8 years 5 months 19 days
Share-based compensation arrangement by share-based payment award, options, outstanding, intrinsic value	$ 0
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
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	$ 13.28
Restricted Stock, Spin-off
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated share-based compensation expense, total			$ 600
2017 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
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	567,424
Percentage of number of common stock shares outstanding	10.00%
Allocated share-based compensation expense, total	$ 5,300	$ 4,400	$ 800
Share-based compensation arrangement by share-based payment award, options, outstanding, exercise price, ending balance	$ 8.73	$ 9.99
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	51.10%	50.40%
Share-based compensation arrangement by share-based payment award, fair value assumptions, discount for postvesting restrictions	2.10%	2.79%
Share-based compensation arrangement by share-based payment award, fair value assumptions, expected term	9 years 9 months	6 years
Share-based compensation arrangement by share-based payment award, options, exercises in period, intrinsic value	$ 1,600
2017 Equity Incentive Plan | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition	1 year 3 months 29 days
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value	$ 13.28	$ 21.63
2017 Equity Incentive Plan | Restricted Stock | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period	1 year
2017 Equity Incentive Plan | Restricted Stock | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period	4 years
2017 Equity Incentive Plan | Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition	1 year 3 months
2017 Equity Incentive Plan | Employee Stock Option | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period	1 year
2017 Equity Incentive Plan | Employee Stock Option | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period	4 years
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
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%
Period of common stock reserved for issuance	10 years

Share Based Compensation - Sche

Share Based Compensation - Schedule of Equity Incentive Plan Transactions (Details) - shares	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding as of the beginning of year (in shares)	805,566		613,700
Granted - 2017 Plan (in shares)	230,503		258,491
Exercised (in shares)	113,750		66,625
Forfeited (in shares)	8,750
Outstanding as of the end of year (in shares)	913,569		805,566
Director Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted (in shares)	30,197		19,285
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding as of the beginning of year (in shares)	192,346		121,693
Granted (in shares)	245,400	[1]	120,600
Vested (in shares)	131,937		49,947
Forfeited (in shares)	2,200
Outstanding as of the end of year (in shares)	303,609		192,346
[1]	Excludes 91,600 grants of performance-based stock units that are not considered outstanding until such time that they become probable to vest.

Share Based Compensation - Sc_2

Share Based Compensation - Schedule of Equity Incentive Plan Transactions (Details) (Parenthetical)	Dec. 31, 2019shares
Performance Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding	91,600

Share Based Compensation - Sc_3

Share Based Compensation - Schedule of Restricted Stock Transactions (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding as of the beginning of year (in shares)	192,346		121,693
Non-Vested, weight average grant price (in dollars per share)	$ 22.32
Granted (in shares)	245,400	[1]	120,600
Granted, weight average grant price (in dollars per share)	$ 13.28
Vested, shares (in shares)	131,937		49,947
Vested, weight average grant price (in dollars per share)	$ 13.45
Forfeited (in shares)	2,200
Forfeited, weight average grant price (in dollars per share)	$ 17.26
Outstanding as of the end of year (in shares)	303,609		192,346
Non-Vested, weight average grant price (in dollars per share)	$ 20.46		$ 22.32
[1]	Excludes 91,600 grants of performance-based stock units that are not considered outstanding until such time that they become probable to vest.

Share Based Compensation - Sc_4

Share Based Compensation - Schedule of Stock Option Transactions (Details) - $ / shares		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Non-Vested, shares (in shares)		805,566
Non-Vested, weight average grant price (in dollars per share)		$ 14.81
Granted, shares (in shares)		230,503	258,491
Granted, weight average grant price (in dollars per share)		$ 8.73
Exercise of options (in shares)		113,750	66,625
Exercised (in dollars per share)		$ 13.98
Forfeited, shares (in shares)		8,750
Forfeited, weight average grant price (in dollars per share)		$ 20.93
Non-Vested, shares (in shares)		913,569	805,566
Non-Vested, weight average grant price (in dollars per share)		$ 14.85	$ 14.81
Exercisable, shares (in shares)	[1]	408,075
Exercisable, weight average grant price (in dollars per share)		$ 14.69
[1]	The weighted average remaining contractual term is 8.23 years.

Share Based Compensation - Sc_5

Share Based Compensation - Schedule of Stock Option Transactions (Details) (Parenthetical)	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-based compensation arrangement by share-based payment award, options, exercisable, weighted average remaining contractual term	8 years 2 months 23 days

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) $ / shares in Units, € in Millions, £ in Millions		Mar. 15, 2019USD ($)shares	Mar. 15, 2019GBP (£)shares	Mar. 15, 2019EUR (€)shares	Jan. 25, 2019USD ($)	Jan. 25, 2019GBP (£)	Jan. 09, 2019shares	Dec. 20, 2018USD ($)	Sep. 28, 2018USD ($)	Sep. 13, 2018USD ($)	May 02, 2018USD ($)$ / sharesshares	Apr. 26, 2018USD ($)$ / sharesshares	Mar. 26, 2018shares	Dec. 01, 2015USD ($)	Apr. 30, 2018USD ($)$ / sharesshares	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 28, 2018
Related Party Transaction [Line Items]
Related Party Transaction, Rate																								0.50%
Interest Expense, Related Party																								$ 200,000	$ 300,000	$ 300,000
Related Party Transaction, Amounts of Transaction																										11,214,000
Percentage of reimbursement of severance and restructuring cost																								50.00%
Equity method investment, ownership percentage								49.00%
Issuance of Common Stock (in shares) | shares													103,213
Issuance of Common Stock																								$ 6,596,000	42,996,000
Indebtedness								$ 95,000,000
Contributed capital								$ 10,000,000
Operating Revenues																$ 49,070,000	$ 54,700,000	$ 52,812,000	$ 44,910,000	$ 58,897,000	$ 58,169,000	$ 47,871,000	$ 38,630,000	201,492,000	203,567,000	123,421,000
Sale of subsidiary to joint venture																									$ 8,017,000
Mexmar Offshore International
Related Party Transaction [Line Items]
Equity method investment, ownership percentage								49.00%
Noncontrolling interest, ownership percentage by noncontrolling owners								51.00%
Offshore Vessel Holdings
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners																											51.00%
Contributed capital																								10,000,000
Financing agreement																								$ 2,400,000
Private Placement
Related Party Transaction [Line Items]
Issuance of Common Stock (in shares) | shares							603,872					56,900,000			750,000
Issuance of Common Stock												$ 56,855,000			$ 15,000,000
Warrants Issued in Private Placement
Related Party Transaction [Line Items]
Class of warrant or right, exercise price of warrants or rights | $ / shares												$ 0.01			$ 0.01
Class of warrant or right, outstanding | shares												2,168,586			2,168,586
Class of warrant or right, number of securities called by warrants or rights | shares												674,164			674,164
Convertible Senior Notes 3.75%
Related Party Transaction [Line Items]
Convertible debt, total											$ 125,000,000			$ 175,000,000	$ 125,000,000
Debt instrument, convertible, conversion ratio																									23.26
Debt instrument, face amount																				1,000					$ 1,000
Debt instrument, interest rate											4.25%			3.75%	4.25%
Lender Non Recourse
Related Party Transaction [Line Items]
Indebtedness								$ 70,000,000
Carlyle Group
Related Party Transaction [Line Items]
Convertible debt, total														$ 175,000,000
Interest rate term																								Interest on the Convertible Notes is payable semi-annually on June 15 and December 15 of each year, commencing June 15, 2016
Debt instrument, convertible, terms of conversion feature																								Carlyle has not exercised this right subsequent to Mr. Hussein’s resignation but retains the right to appoint a Board member. Mr. Hussein has been designated by Carlyle to observe meetings of the Board pursuant to Carlyle’s observer rights under the Convertible Notes. This observation right will terminate at the time Carlyle owns less than $50.0 million in aggregate principal amount of the Convertible Notes or a combination of the Convertible Notes and our Common Stock representing less than 5.0% of the Company’s Common Stock outstanding on a fully diluted basis, assuming the conversion of all of the Convertible Notes and Warrants to purchase Common Stock held by Carlyle.
Carlyle Group | Convertible Senior Notes Converted to Warrants
Related Party Transaction [Line Items]
Debt conversion, original debt, amount											$ 50,000,000				$ 50,000,000
Class of warrant or right, exercise price of warrants or rights | $ / shares											$ 0.01				$ 0.01
Debt instrument, convertible, conversion ratio											37.73				37.73
Debt instrument, face amount											$ 1,000				$ 1,000
Debt instrument, convertible, conversion price | $ / shares											$ 26.50				$ 26.50
Debt conversion, converted instrument, shares issued | shares											1,886,792				1,900,000
Windcat Workboats Facilities | Seabulk Overseas
Related Party Transaction [Line Items]
Business acquisition, percentage of voting interests acquired		6.25%	6.25%	6.25%	6.25%	6.25%										100.00%								100.00%
Ownership Percentage					100.00%	100.00%
Business combination, consideration transferred, total		$ 1,400,000	£ 1.2	€ 1.2	$ 2,000,000	£ 1.6
Business acquisition, exchange for consideration | shares		50,000	50,000	50,000
OSV Partners
Related Party Transaction [Line Items]
Revenue from related parties																								$ 0	600,000	600,000
Proceeds from Sale of Interest in Partnership Unit																									7,500,000
Equity method investment, ownership percentage																30.40%								30.40%
Contributed capital									$ 5,000,000																	2,300,000
OSV Partners | Limited Partner | Llorca
Related Party Transaction [Line Items]
Limited Partners' Capital Account, Total																$ 400,000								$ 400,000
OSV Partners | General Partner
Related Party Transaction [Line Items]
Equity method investment, ownership percentage																38.60%								38.60%
Contributed capital																										6,000,000
OSV Partners | Second Lien Debt
Related Party Transaction [Line Items]
Proceeds from issuance of debt																									5,000,000
Equity method investment, ownership percentage																43.00%								43.00%
OSV Partners | Series A Preferred Stock
Related Party Transaction [Line Items]
Proceeds from Issuance of Redeemable Preferred Stock																									2,500,000
Proceeds From issuance of additional redeemable preferred stock																									2,500,000
Equity method investment, ownership percentage																43.00%								43.00%
CME
Related Party Transaction [Line Items]
Contributed capital								5,000,000
CME | Private Placement
Related Party Transaction [Line Items]
Issuance of Common Stock (in shares) | shares												325,836
Issuance of Common Stock												$ 20,000,000
CME | Warrants Issued in Private Placement
Related Party Transaction [Line Items]
Class of warrant or right, number of securities called by warrants or rights | shares												674,164
MexMar
Related Party Transaction [Line Items]
Revenue from related parties																								$ 300,000	300,000	300,000
Equity method investment, ownership percentage																49.00%								49.00%
Indebtedness								15,000,000
Operating Revenues																									16,500,000
Capital distributions from equity investees										$ 9,800,000														$ 0	9,800,000
MEXMAR Offshore
Related Party Transaction [Line Items]
Equity method investment, ownership percentage	[1]															49.00%								49.00%
Indebtedness								10,000,000
Contributed capital								$ 5,000,000
SEACOR Marlin LLC
Related Party Transaction [Line Items]
Equity method investment, ownership percentage																49.00%								49.00%
Equity method investment, ownership, percent sold										51.00%
Sale of subsidiary to joint venture										$ 8,000,000
JMG GST LLC
Related Party Transaction [Line Items]
Issuance of Common Stock (in shares) | shares																								50,000
Issuance of Common Stock																								$ 1,000,000
Restricted Stock
Related Party Transaction [Line Items]
Adjustments to Additional Paid in Capital, Other																								$ 2,700,000
Stock issued during period, shares, restricted stock award, gross | shares																								120,693
Share Distribution
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction																								$ 6,700,000
Transition Services Agreement
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction																								$ 600,000	4,500,000	3,300,000
Maximum
Related Party Transaction [Line Items]
Equity method investment, ownership percentage																50.00%								50.00%
Maximum | Carlyle Group
Related Party Transaction [Line Items]
Convertible debt, total																										$ 50,000,000
Percentage of convertible notes converted into common stock																										5
Maximum | Transition Services Agreement
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction																								$ 6,300,000
Minimum
Related Party Transaction [Line Items]
Equity method investment, ownership percentage																20.00%								20.00%
Minimum | Carlyle Group
Related Party Transaction [Line Items]
Percentage of convertible notes converted into common stock														10
Restructuring Charges
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction																								$ 6,000,000
Restructuring Charges | Maximum
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction																								3,000,000
Severance Liability
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction																								0	0	$ 700,000
SEACOR Holdings
Related Party Transaction [Line Items]
Revenue from related parties																										$ 100,000
Guarantor Obligations, Maximum Exposure, Undiscounted																$ 22,800,000				$ 40,600,000				22,800,000	$ 40,600,000
Related Party Transaction, Amounts of Transaction																								9,400,000
Allocated share-based compensation expense, total																								1,700,000
Officer | OSV Partners | Limited Partner | Fabrikant
Related Party Transaction [Line Items]
Limited Partners' Capital Account, Total																300,000								300,000
Officer | OSV Partners | Limited Partner | Gellert
Related Party Transaction [Line Items]
Limited Partners' Capital Account, Total																$ 200,000								$ 200,000
Officer | OSV Partners | Limited Partner | Fabrikant And Gellert
Related Party Transaction [Line Items]
Equity method investment, ownership percentage																39.60%								39.60%
Officer | OSV Partners | Second Lien Debt | General Partner
Related Party Transaction [Line Items]
Equity method investment, ownership percentage																3.90%								3.90%
General Partners' Capital Account, Total																$ 200,000								$ 200,000
Officer | OSV Partners | Series A Preferred Stock | General Partner
Related Party Transaction [Line Items]
Equity method investment, ownership percentage																3.90%								3.90%
General Partners' Capital Account, Total																$ 200,000								$ 200,000
Officer | Maximum | OSV Partners
Related Party Transaction [Line Items]
Limited Partners' Capital Account, Total																$ 1,500,000								$ 1,500,000
Officer | Maximum | OSV Partners | Limited Partner
Related Party Transaction [Line Items]
Equity method investment, ownership percentage																3.90%								3.90%
Officer | Maximum | OSV Partners | General Partner
Related Party Transaction [Line Items]
Equity method investment, ownership percentage																5.00%								5.00%
General Partners' Capital Account, Total																$ 300,000								$ 300,000
[1]	This joint venture holds the investment in UP Offshore

Related Party Transactions - Re

Related Party Transactions - Related Party Transactions (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Related Party Transaction [Line Items]
Related party transactions	$ 11,214
Health Insurance
Related Party Transaction [Line Items]
Related party transactions	899
Stock Compensation Plan
Related Party Transaction [Line Items]
Related party transactions	8,383
Management Services
Related Party Transaction [Line Items]
Related party transactions	$ 1,932

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) R$ in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Feb. 28, 2015USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2019BRL (R$)
Commitments And Contingencies [Line Items]
Unrecorded unconditional purchase obligation, total		$ 35.9
Unrecorded unconditional purchase obligation due within four years		30.2
Windcat Workboats Holdings Ltd
Commitments And Contingencies [Line Items]
Line of credit facility remaining borrowing capacity		$ 2
Deficiency Notice
Commitments And Contingencies [Line Items]
Cost allocation percentage		70.00%
Deposited with Court	$ 1.2
Deficiency Notice | Seabulk Overseas
Commitments And Contingencies [Line Items]
Cost allocation percentage		30.00%
Minimum | Deficiency Notice
Commitments And Contingencies [Line Items]
Potential range of levies		$ 3.2	R$ 12.8
Maximum | Deficiency Notice
Commitments And Contingencies [Line Items]
Potential range of levies		$ 4.3	R$ 17.5
Platform Supply Vessels
Commitments And Contingencies [Line Items]
Unrecorded unconditional purchase obligation, maximum quantity		4	4
Crew Transfer Vessels
Commitments And Contingencies [Line Items]
Unrecorded unconditional purchase obligation, maximum quantity		1	1
FSV Offshore Support Vessels
Commitments And Contingencies [Line Items]
Unrecorded unconditional purchase obligation, maximum quantity		3	3

Major Customers and Segment I_3

Major Customers and Segment Information - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenue from contract with customer, including assessed tax	$ 49,070	$ 54,700	$ 52,812	$ 44,910	$ 58,897	$ 58,169	$ 47,871	$ 38,630	$ 201,492	$ 203,567	$ 123,421
Income (loss) from equity method investments									(14,304)	(3,552)	3,851
Customer Concentration Risk | Sales Revenue, Net | Seacor Marine Arabia LLC
Segment Reporting Information [Line Items]
Revenue from contract with customer, including assessed tax									$ 30,800	$ 21,400	$ 16,000
Concentration risk, percentage									15.00%	10.00%	13.00%
Customer Concentration Risk | Sales Revenue, Net | Ten Largest Customers
Segment Reporting Information [Line Items]
Concentration risk, percentage									44.00%	49.00%	58.00%
Geographic Concentration Risk | Sales Revenue, Net | Non-US
Segment Reporting Information [Line Items]
Income (loss) from equity method investments									$ (12,800)	$ (3,000)	$ 2,000
Geographic Concentration Risk | Sales Revenue, Net | Zamil Offshore
Segment Reporting Information [Line Items]
Revenue from contract with customer, including assessed tax									$ 20,300	$ 12,200	$ 4,500
Concentration risk, percentage									10.00%	6.00%	4.00%
Geographic Concentration Risk | Sales Revenue, Net | Saudi Aramco
Segment Reporting Information [Line Items]
Revenue from contract with customer, including assessed tax									$ 10,500	$ 9,200	$ 11,200
Concentration risk, percentage									5.00%	4.00%	9.00%
Geographic Concentration Risk | Stockholders' Equity | Non-US
Segment Reporting Information [Line Items]
Concentration risk, percentage									78.00%	36.00%	82.00%

Major Customers and Segment I_4

Major Customers and Segment Information - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Segment Reporting Information [Line Items]
Operating Revenues	$ 49,070		$ 54,700	$ 52,812	$ 44,910	$ 58,897		$ 58,169	$ 47,871	$ 38,630	$ 201,492		$ 203,567		$ 123,421
Direct Costs and Expenses											123,725		132,274		104,821
Direct Vessel Profit											77,767		71,293		18,600
Administrative and general											44,726		46,454		49,865
Depreciation and amortization											64,012		68,841		60,307
Other Costs and Expenses											124,896		128,534		124,621
Losses on Asset Dispositions and Impairments, Net											(5,397)		(11,268)		(23,623)
Operating Loss	(10,497)		$ (3,355)	$ (17,640)	$ (21,034)	(11,253)		$ (12,207)	$ (20,842)	$ (24,206)	(52,526)		(68,509)		(129,644)
Historical cost	976,978	[1]				1,116,583	[1]				976,978	[1]	1,116,583	[1]	1,058,304
Accumulated depreciation	(358,962)					(461,399)					(358,962)		(461,399)		(459,892)
Property and equipment	618,016					655,184					618,016		655,184		598,412
Total Assets	863,644	[2]				908,285	[3]				863,644	[2]	908,285	[3]	802,104	[4]
Leased In Equipment
Segment Reporting Information [Line Items]
Operating expenses											16,158		13,239		14,449
Time Charter
Segment Reporting Information [Line Items]
Operating Revenues											182,301		172,350		110,322
Bareboat Charter
Segment Reporting Information [Line Items]
Operating Revenues											5,131		4,635		4,636
Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues											14,060		26,582		8,463
Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses											65,512		67,313		54,613
Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses											24,669		27,033		21,324
Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses											5,848		7,793		4,976
Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses											6,038		6,343		6,029
Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses											11,327		13,509		8,746
Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses											10,331		10,283		9,133
UNITED STATES
Segment Reporting Information [Line Items]
Operating Revenues											44,323		53,564		22,296
Direct Costs and Expenses											35,367		32,700		26,063
Direct Vessel Profit											8,956		20,864		(3,767)
Depreciation and amortization											21,947		23,227		22,060
Historical cost	297,392					432,336					297,392		432,336		410,475
Accumulated depreciation	(157,514)					(224,737)					(157,514)		(224,737)		(230,636)
Property and equipment	139,878					207,599					139,878		207,599		179,839
Total Assets	224,229	[2]				351,748	[3]				224,229	[2]	351,748	[3]	310,675	[4]
UNITED STATES | Leased In Equipment
Segment Reporting Information [Line Items]
Operating expenses											10,894		8,240		8,709
UNITED STATES | Time Charter
Segment Reporting Information [Line Items]
Operating Revenues											38,955		38,802		18,079
UNITED STATES | Bareboat Charter
Segment Reporting Information [Line Items]
Operating Revenues											1,562
UNITED STATES | Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues											3,806		14,762		4,217
UNITED STATES | Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses											17,491		18,708		15,621
UNITED STATES | Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses											7,583		5,152		3,594
UNITED STATES | Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses											4,594		1,957		1,828
UNITED STATES | Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses											2,370		2,922		3,286
UNITED STATES | Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses											2,936		3,568		1,485
UNITED STATES | Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses											393		393		249
Africa
Segment Reporting Information [Line Items]
Operating Revenues											45,621		51,508		33,946
Direct Costs and Expenses											27,900		34,188		28,367
Direct Vessel Profit											17,721		17,320		5,579
Depreciation and amortization											10,404		10,453		9,280
Historical cost	207,107					184,361					207,107		184,361		192,600
Accumulated depreciation	(57,136)					(55,206)					(57,136)		(55,206)		(57,228)
Property and equipment	149,971					129,155					149,971		129,155		135,372
Total Assets	161,915	[2]				140,335	[3]				161,915	[2]	140,335	[3]	140,173	[4]
Africa | Leased In Equipment
Segment Reporting Information [Line Items]
Operating expenses											3,090		4,281		4,317
Africa | Time Charter
Segment Reporting Information [Line Items]
Operating Revenues											44,160		43,847		32,866
Africa | Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues											1,461		7,661		1,080
Africa | Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses											13,833		16,538		13,419
Africa | Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses											4,701		6,330		5,957
Africa | Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses											490		2,085		2,180
Africa | Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses											1,051		1,096		677
Africa | Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses											3,471		3,826		2,815
Africa | Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses											4,354		4,313		3,319
Middle East and Asia
Segment Reporting Information [Line Items]
Operating Revenues											55,981		49,185		33,884
Direct Costs and Expenses											31,928		38,718		37,299
Direct Vessel Profit											24,053		10,467		(3,415)
Depreciation and amortization											16,400		18,762		17,724
Historical cost	292,446					306,897					292,446		306,897		326,378
Accumulated depreciation	(73,039)					(81,378)					(73,039)		(81,378)		(100,435)
Property and equipment	219,407					225,519					219,407		225,519		225,943
Total Assets	250,890	[2]				260,002	[3]				250,890	[2]	260,002	[3]	234,471	[4]
Middle East and Asia | Leased In Equipment
Segment Reporting Information [Line Items]
Operating expenses											173		224		1,092
Middle East and Asia | Time Charter
Segment Reporting Information [Line Items]
Operating Revenues											54,312		50,072		33,410
Middle East and Asia | Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues											1,669		(887)		474
Middle East and Asia | Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses											16,698		16,806		16,883
Middle East and Asia | Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses											7,182		11,172		9,037
Middle East and Asia | Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses											600		1,362		968
Middle East and Asia | Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses											1,449		1,371		1,444
Middle East and Asia | Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses											2,904		4,027		3,727
Middle East and Asia | Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses											3,095		3,980		5,240
Latin America
Segment Reporting Information [Line Items]
Operating Revenues											16,419		23,532		8,165
Direct Costs and Expenses											8,517		8,388		1,739
Direct Vessel Profit											7,902		15,144		6,426
Depreciation and amortization											6,205		7,908		3,608
Historical cost	57,534					124,177					57,534		124,177		72,484
Accumulated depreciation	(16,239)					(57,002)					(16,239)		(57,002)		(37,281)
Property and equipment	41,295					67,175					41,295		67,175		35,203
Total Assets	116,736	[2]				137,983	[3]				116,736	[2]	137,983	[3]	103,135	[4]
Latin America | Leased In Equipment
Segment Reporting Information [Line Items]
Operating expenses											10		5		5
Latin America | Time Charter
Segment Reporting Information [Line Items]
Operating Revenues											11,460		17,343		2,977
Latin America | Bareboat Charter
Segment Reporting Information [Line Items]
Operating Revenues											3,569		4,635		4,636
Latin America | Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues											1,390		1,554		552
Latin America | Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses											4,459		4,399		809
Latin America | Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses											1,348		1,011		274
Latin America | Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses											161		128
Latin America | Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses											311		495		316
Latin America | Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses											1,056		1,225		223
Latin America | Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses											1,182		1,130		117
Europe Continuing Operations
Segment Reporting Information [Line Items]
Operating Revenues											39,148		25,778		25,130
Direct Costs and Expenses											20,013		18,280		11,353
Direct Vessel Profit											19,135		7,498		13,777
Depreciation and amortization											9,056		8,491		7,635
Historical cost	122,499					68,812					122,499		68,812		56,367
Accumulated depreciation	(55,034)					(43,076)					(55,034)		(43,076)		(34,312)
Property and equipment	67,465					25,736					67,465		25,736		22,055
Total Assets	$ 109,874	[2]				$ 18,217	[3]				109,874	[2]	18,217	[3]	13,650	[4]
Europe Continuing Operations | Leased In Equipment
Segment Reporting Information [Line Items]
Operating expenses											1,991		489		326
Europe Continuing Operations | Time Charter
Segment Reporting Information [Line Items]
Operating Revenues											33,414		22,286		22,990
Europe Continuing Operations | Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues											5,734		3,492		2,140
Europe Continuing Operations | Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses											13,031		10,862		7,881
Europe Continuing Operations | Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses											3,855		3,368		2,462
Europe Continuing Operations | Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses											3		2,261
Europe Continuing Operations | Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses											857		459		306
Europe Continuing Operations | Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses											960		863		496
Europe Continuing Operations | Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses											$ 1,307		$ 467		$ 208
[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 $145,232 thousand of corporate assets.
[3]	Total assets exclude $153,151 thousand of corporate assets, and $41,502 thousand of assets held-for-sale.
[4]	Total assets exclude $169,346 thousand of corporate assets, and $37,054 thousand of assets held-for-sale.

Major Customers and Segment I_5

Major Customers and Segment Information - Schedule of Segment Reporting Information, by Segment (Parenthetical) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Assets, Total	$ 1,009,193	$ 1,102,938
Assets held for sale		41,502	$ 37,054
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Assets, Total	$ 145,232	$ 153,151	$ 169,346

Supplemental Information for _3

Supplemental Information for Statements of Cash Flows - Schedule of Supplemental Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Income taxes (paid) refunded, net	$ 1,999	$ (316)	$ 33,773
Interest paid, excluding capitalized interest	$ 22,452	$ 21,031	$ 9,216

Discontinued Operations - Sched

Discontinued Operations - Schedule of Assets Held for Sale (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets from Discontinued Operations:
Current assets		$ 15,222
Assets from discontinued operations		41,502	$ 37,054
Total current liabilities		2,526
Other Income (Expense)
Net (Loss) Income from Discontinued Operations	$ (9,106)
BPOS | Discontinued Operations, Held-for-sale
Assets from Discontinued Operations:
Current assets		15,222
Net property and equipment		26,280
Assets from discontinued operations		41,502
Total current liabilities		2,526
Operating Revenues:
Operating Revenues	41,259	50,042
Costs and Expenses:
Operating	33,836	42,817
Direct Vessel Profit	7,423	7,225
Depreciation	3,504	3,405
General and Administrative Expenses	4,207	4,524
Lease Expense	60	71
(Loss) Gain on Asset Dispositions and Impairments, Net	91	2,521
Operating (Loss) Income	(257)	1,746
Other Income (Expense)
Interest income	11	12
Interest expense	210	465
Foreign currency translation loss	(75)	(53)
Other Income (Expense)	(274)	(506)
Operating (Loss) Income Before Equity Earnings of 50% or Less Owned Companies, Net of Tax	(531)	1,240
Income Tax Expense	(2)	7
Operating (Loss) Income Before Equity Earnings of 50% or Less Owned Companies	(529)	1,233
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	168	137
Net (Loss) Income from Discontinued Operations	(361)	1,370
BPOS | Discontinued Operations, Held-for-sale | Time Charter
Operating Revenues:
Operating Revenues	41,214	49,902
BPOS | Discontinued Operations, Held-for-sale | Other Revenue
Operating Revenues:
Operating Revenues	$ 45	$ 140

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ in Thousands	Feb. 07, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 08, 2018
Repayments of long-term debt, total		$ 23,974	$ 49,405	$ 11,926
Omnibus Amendment | Term and Revolving Loan Facility
Debt agreement maximum borrowing capacity					$ 131,100
Omnibus Amendment | Subsequent Event
Repayment terms	the extension from March 2020 to March 2021 of the commencement of monthly repayment of the term loan, with payments being the lesser of (a) $0.8 million per month and (b) the amount outstanding under the term loan
Repayments of long-term debt, total	$ 800
Extension term of Guaranty	1 year
Outstanding principal amount	$ 117,300
Omnibus Amendment | Subsequent Event | Term Loan Facility
Outstanding principal amount	102,300
Omnibus Amendment | Subsequent Event | Revolving Credit Facility
Outstanding principal amount	$ 15,000

Quarterly Financial Informati_3

Quarterly Financial Information (Unaudited) - Selected Financial Information for Interim Quarterly Periods (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Operating Revenues	$ 49,070	$ 54,700	$ 52,812	$ 44,910	$ 58,897	$ 58,169	$ 47,871	$ 38,630	$ 201,492	$ 203,567	$ 123,421
Operating Loss	(10,497)	(3,355)	(17,640)	(21,034)	(11,253)	(12,207)	(20,842)	(24,206)	(52,526)	(68,509)	(129,644)
Net (Loss) Income:
Continuing Operations	(19,176)	(10,341)	(31,438)	(28,273)	(7,780)	(17,706)	(26,505)	(31,430)	(89,228)	(83,422)	(39,529)
Discontinued Operations	(2,742)	(7,899)	1,174		(189)	1,940	(124)	(258)
Net Loss	(21,918)	(18,240)	(30,264)	(28,273)	(7,969)	(15,766)	(26,629)	(31,688)	(98,695)	(82,052)	(38,540)
Net Loss attributable to SEACOR Marine Holdings Inc:	$ (20,455)	$ (18,444)	$ (28,389)	$ (25,549)	$ (7,794)	$ (15,957)	$ (25,024)	$ (28,833)	$ (92,837)	$ (77,608)	$ (32,901)
Basic and Diluted Income (Loss) Per Common Share and Warrants of SEACOR Marine Holdings Inc.
Continuing operations	$ (0.74)	$ (0.49)	$ (1.31)	$ (1.16)	$ (0.39)	$ (0.85)	$ (1.18)	$ (1.63)	$ (3.55)	$ (3.77)	$ (1.93)
Discontinued operations	(0.12)	(0.29)	0.10	0.05	0.04	0.14	(0.01)	(0.01)	(0.40)	0.07	0.06
Basic and Diluted Income (Loss) Per Common Share and Warrants	$ (0.86)	$ (0.78)	$ (1.21)	$ (1.11)	$ (0.35)	$ (0.71)	$ (1.19)	$ (1.64)	$ (3.95)	$ (3.70)	$ (1.87)

Schedule II - Valuation and Q_3

Schedule II - Valuation and Qualifying Accounts - Schedule of Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation And Qualifying Accounts [Abstract]
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)		(405)	(928)	(1,283)
Allowance for doubtful accounts (deducted from trade and notes receivable)	[1]		(2,251)	(37)
Allowance for doubtful accounts (deducted from trade and notes receivable)		$ 455	$ 860	$ 4,039
[1]	Trade receivable amounts deemed uncollectible that were removed from accounts receivable and allowance for doubtful accounts.