Helix Energy Solutions (HLX) 10-Q 22 Oct 21 2021 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Oct. 18, 2021
Document And Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-32936
Entity Registrant Name	HELIX ENERGY SOLUTIONS GROUP, INC.
Entity Incorporation, State or Country Code	MN
Entity Tax Identification Number	95-3409686
Entity Address, Address Line One	3505 West Sam Houston Parkway North
Entity Address, Address Line Two	Suite 400
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77043
City Area Code	281
Local Phone Number	618–0400
Title of 12(b) Security	Common Stock
Trading Symbol	HLX
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		150,888,686
Entity Central Index Key	0000866829
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 237,549	$ 291,320
Restricted cash	71,282
Accounts receivable, net of allowance for credit losses of $1,410 and $3,469, respectively	136,704	132,233
Other current assets	62,442	102,092
Total current assets	507,977	525,645
Property and equipment	2,942,699	2,948,907
Less accumulated depreciation	(1,256,025)	(1,165,943)
Property and equipment, net	1,686,674	1,782,964
Operating lease right-of-use assets	117,397	149,656
Other assets, net	35,251	40,013
Total assets	2,347,299	2,498,278
Current liabilities:
Accounts payable	75,162	50,022
Accrued liabilities	85,240	87,035
Current maturities of long-term debt	42,825	90,651
Current operating lease liabilities	55,051	51,599
Total current liabilities	258,278	279,307
Long-term debt	261,668	258,912
Operating lease liabilities	64,423	101,009
Deferred tax liabilities	91,785	110,821
Other non-current liabilities	1,481	3,878
Total liabilities	677,635	753,927
Commitments and contingencies
Redeemable noncontrolling interests		3,855
Shareholders' equity:
Common stock, no par, 240,000 shares authorized, 150,876 and 150,341 shares issued, respectively	1,290,697	1,327,592
Retained earnings	437,065	464,524
Accumulated other comprehensive loss	(58,098)	(51,620)
Total shareholders' equity	1,669,664	1,740,496
Total liabilities, redeemable noncontrolling interests and shareholders' equity	$ 2,347,299	$ 2,498,278

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Allowance for credit losses	$ 1,410	$ 3,469
Shareholders' equity:
Common stock, par value (USD per share)	$ 0	$ 0
Common stock, shares authorized	240,000	240,000
Common stock, shares issued	150,876	150,341

Condensed Consolidated Statemen

Condensed Consolidated Statements Of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Net revenues	$ 180,716	$ 193,490	$ 506,072	$ 573,658
Cost of sales	177,716	158,862	485,318	507,444
Gross profit	3,000	34,628	20,754	66,214
Gain (loss) on disposition of assets, net	15	440	(631)	913
Goodwill impairment				(6,689)
Selling, general and administrative expenses	(13,346)	(16,053)	(41,950)	(48,256)
Income (loss) from operations	(10,331)	19,015	(21,827)	12,182
Net interest expense	(5,928)	(7,598)	(17,900)	(20,407)
Gain (loss) on extinguishment of long-term debt	(124)	9,239	(124)	9,239
Other income (expense), net	(4,015)	8,824	(1,438)	(3,672)
Royalty income and other	297	197	2,603	2,493
Income (loss) before income taxes	(20,101)	29,677	(38,686)	(165)
Income tax provision (benefit)	(1,058)	5,232	(2,910)	(16,132)
Net income (loss)	(19,043)	24,445	(35,776)	15,967
Net loss attributable to redeemable noncontrolling interests		(54)	(146)	(2,044)
Net income (loss) attributable to common shareholders	$ (19,043)	$ 24,499	$ (35,630)	$ 18,011
Earnings (loss) per share of common stock:
Basic	$ (0.13)	$ 0.16	$ (0.24)	$ 0.10
Diluted	$ (0.13)	$ 0.16	$ (0.24)	$ 0.10
Weighted average common shares outstanding (in shares)
Basic	150,088	149,032	150,018	148,956
Diluted	150,088	149,951	150,018	149,824

Condensed Consolidated Statem_2

Condensed Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (19,043)	$ 24,445	$ (35,776)	$ 15,967
Other comprehensive income (loss), net of tax:
Net unrealized loss on hedges arising during the period				(95)
Reclassifications into earnings				452
Income taxes on hedges				(72)
Net change in hedges, net of tax				285
Foreign currency translation gain (loss)	(13,447)	19,426	(6,478)	(16,057)
Other comprehensive income (loss), net of tax	(13,447)	19,426	(6,478)	(15,772)
Comprehensive income (loss)	(32,490)	43,871	(42,254)	195
Less comprehensive income (loss) attributable to redeemable noncontrolling interests:
Net loss		(54)	(146)	(2,044)
Foreign currency translation gain (loss)		133	48	(115)
Comprehensive income (loss) attributable to redeemable noncontrolling interests		79	(98)	(2,159)
Comprehensive income (loss) attributable to common shareholders	$ (32,490)	$ 43,792	$ (42,156)	$ 2,354

Condensed Consolidated Statem_3

Condensed Consolidated Statements Of Shareholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common StockCumulative Effect, Period of Adoption	Common Stock	Retained EarningsCumulative Effect, Period of Adoption	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Cumulative Effect, Period of Adoption	Total
Balance, beginning of period (Accounting Standards Update 2016-13) at Dec. 31, 2019			$ (620)			$ (620)
Balance, beginning of period at Dec. 31, 2019		$ 1,318,961		$ 445,370	$ (64,740)		$ 1,699,591
Balance, beginning of period (in shares) at Dec. 31, 2019		148,888
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)				18,011			18,011
Foreign currency translation adjustments					(16,057)		(16,057)
Unrealized gain on hedges, net of tax					285		285
Accretion of redeemable noncontrolling interests				(2,283)			(2,283)
Equity component of convertible senior notes		$ 33,336					33,336
Re-acquisition of equity component of convertible senior notes		(18,006)					(18,006)
Capped call transactions		(10,625)					(10,625)
Activity in company stock plans, net and other		$ (4,320)					(4,320)
Activity in company stock plans, net and other (in shares)		1,248
Share-based compensation		$ 6,174					6,174
Balance, end of period at Sep. 30, 2020		$ 1,325,520		460,478	(80,512)		1,705,486
Balance, end of period (in shares) at Sep. 30, 2020		150,136
Balance, beginning of period at Dec. 31, 2019							3,455
Increase (Decrease) in Redeemable Noncontrolling Interests [Roll Forward]
Net income (loss)							(2,044)
Foreign currency translation adjustments related to redeemable noncontrolling interests							(115)
Accretion of redeemable noncontrolling interests							2,283
Balance, end of period at Sep. 30, 2020							3,579
Balance, beginning of period at Jun. 30, 2020		$ 1,318,531		436,107	(99,938)		1,654,700
Balance, beginning of period (in shares) at Jun. 30, 2020		150,040
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)				24,499			24,499
Foreign currency translation adjustments					19,426		19,426
Accretion of redeemable noncontrolling interests				(128)			(128)
Equity component of convertible senior notes		$ 33,336					33,336
Re-acquisition of equity component of convertible senior notes		(18,006)					(18,006)
Capped call transactions		(10,625)					(10,625)
Activity in company stock plans, net and other		$ 193					193
Activity in company stock plans, net and other (in shares)		96
Share-based compensation		$ 2,091					2,091
Balance, end of period at Sep. 30, 2020		$ 1,325,520		460,478	(80,512)		1,705,486
Balance, end of period (in shares) at Sep. 30, 2020		150,136
Balance, beginning of period at Jun. 30, 2020							3,372
Increase (Decrease) in Redeemable Noncontrolling Interests [Roll Forward]
Net income (loss)							(54)
Foreign currency translation adjustments related to redeemable noncontrolling interests							133
Accretion of redeemable noncontrolling interests							128
Balance, end of period at Sep. 30, 2020							3,579
Balance, beginning of period (Accounting Standards Update 2020-06 [Member]) at Dec. 31, 2020	$ (41,456)		$ 6,682			$ (34,774)
Balance, beginning of period at Dec. 31, 2020		$ 1,327,592		464,524	(51,620)		1,740,496
Balance, beginning of period (in shares) at Dec. 31, 2020		150,341
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)				(35,630)			(35,630)
Foreign currency translation adjustments					(6,478)		(6,478)
Accretion of redeemable noncontrolling interests							(241)
Accretion of redeemable noncontrolling interests				1,489			1,489
Activity in company stock plans, net and other		$ (1,052)					(1,052)
Activity in company stock plans, net and other (in shares)		535
Share-based compensation		$ 5,613					5,613
Balance, end of period at Sep. 30, 2021		$ 1,290,697		437,065	(58,098)		1,669,664
Balance, end of period (in shares) at Sep. 30, 2021		150,876
Balance, beginning of period at Dec. 31, 2020							3,855
Increase (Decrease) in Redeemable Noncontrolling Interests [Roll Forward]
Net income (loss)							(146)
Foreign currency translation adjustments related to redeemable noncontrolling interests							48
Accretion of redeemable noncontrolling interests							(1,489)
Acquisition of redeemable noncontrolling interests							(2,268)
Balance, beginning of period at Jun. 30, 2021		$ 1,288,603		456,108	(44,651)		1,700,060
Balance, beginning of period (in shares) at Jun. 30, 2021		150,787
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)				(19,043)			(19,043)
Foreign currency translation adjustments					(13,447)		(13,447)
Activity in company stock plans, net and other		$ 262					262
Activity in company stock plans, net and other (in shares)		89
Share-based compensation		$ 1,832					1,832
Balance, end of period at Sep. 30, 2021		$ 1,290,697		$ 437,065	$ (58,098)		$ 1,669,664
Balance, end of period (in shares) at Sep. 30, 2021		150,876

Condensed Consolidated Statem_4

Condensed Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Net income (loss)	$ (35,776)	$ 15,967
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	106,226	99,552
Goodwill impairment		6,689
Amortization of debt discounts		5,094
Amortization of debt issuance costs	2,596	2,401
Share-based compensation	5,783	6,394
Deferred income taxes	(10,375)	3,901
(Gain) loss on disposition of assets, net	631	(913)
(Gain) loss on extinguishment of long-term debt	124	(9,239)
Unrealized gain on derivative contracts, net		(601)
Unrealized foreign currency loss	2,041	2,891
Changes in operating assets and liabilities:
Accounts receivable, net	(6,631)	(35,276)
Other current assets	16,604	(28,036)
Income tax payable, net of income tax receivable	20,912	(26,342)
Accounts payable and accrued liabilities	28,577	32,075
Other, net	9,460	15,929
Net cash provided by operating activities	121,252	58,628
Cash flows from investing activities:
Capital expenditures	(7,386)	(19,193)
Proceeds from sale of assets	51	938
Net cash used in investing activities	(7,335)	(18,255)
Cash flows from financing activities:
Proceeds from convertible senior notes		200,000
Repayment of convertible senior notes		(183,150)
Capped call transactions		(10,625)
Debt issuance costs	(1,209)	(7,075)
Acquisition of redeemable noncontrolling interests	(2,268)
Payments related to tax withholding for share-based compensation	(1,878)	(5,161)
Proceeds from issuance of ESPP shares	654	622
Net cash used in financing activities	(95,659)	(42,000)
Effect of exchange rate changes on cash and cash equivalents and restricted cash	(747)	(1,600)
Net increase (decrease) in cash and cash equivalents and restricted cash	17,511	(3,227)
Cash and cash equivalents and restricted cash:
Balance, beginning of year	291,320	262,561
Balance, end of period	308,831	259,334
Term Loan Repaid September 2021
Cash flows from financing activities:
Repayment of loan debt	(29,826)	(2,625)
Nordea Q5000 Loan Matured January 2021
Cash flows from financing activities:
Repayment of loan debt	(53,572)	(26,786)
MARAD Debt Maturing February 2027
Cash flows from financing activities:
Repayment of loan debt	$ (7,560)	$ (7,200)

Basis Of Presentation And New A

Basis Of Presentation And New Accounting Standards	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis Of Presentation And New Accounting Standards	Note 1 — Basis of Presentation and New Accounting Standards The accompanying condensed consolidated financial statements include the accounts of Helix Energy Solutions Group, Inc. and its subsidiaries (collectively, “Helix”). Unless the context indicates otherwise, the terms “we,” “us” and “our” in this report refer collectively to Helix and its subsidiaries. All material intercompany accounts and transactions have been eliminated. These unaudited condensed consolidated financial statements have been prepared pursuant to instructions for the Quarterly Report on Form 10-Q required to be filed with the Securities and Exchange Commission (the “SEC”) and do not include all information and footnotes normally included in annual financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The accompanying condensed consolidated financial statements have been prepared in conformity with GAAP in U.S. dollars and are consistent in all material respects with those applied in our 2020 Annual Report on Form 10-K (our “2020 Form 10-K”) with the exception of the impact of early adopting Accounting Standards Update (“ASU”) No. 2020-06 on a modified retrospective basis beginning January 1, 2021 (see below). The preparation of these financial statements requires us to make estimates and judgments that affect the amounts reported in the financial statements and the related disclosures. Actual results may differ from our estimates. We have made all adjustments, which, unless otherwise disclosed, are of normal recurring nature, that we believe are necessary for a fair presentation of the condensed consolidated balance sheets, statements of operations, statements of comprehensive income, statements of shareholders’ equity and statements of cash flows, as applicable. The operating results for the three- and nine-month periods ended September 30, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021. Our balance sheet as of December 31, 2020 included herein has been derived from the audited balance sheet as of December 31, 2020 included in our 2020 Form 10-K. These unaudited condensed consolidated financial statements should be read in conjunction with the audited annual consolidated financial statements and notes thereto included in our 2020 Form 10-K. Certain reclassifications were made to previously reported amounts in the consolidated financial statements and notes thereto to make them consistent with the current presentation format. New accounting standards In August 2020, the Financial Accounting Standards Board issued ASU No. 2020-06, “Accounting for Convertible Instruments and Contracts in an Entity's Own Equity,” which simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts in an entity’s own equity. Among other changes, this ASU removes from GAAP the requirement to separate certain convertible instruments, such as our Convertible Senior Notes Due 2022, Convertible Senior Notes Due 2023 and Convertible Senior Notes Due 2026 (Note 5), into liability and equity components. Consequently, those convertible instruments will be accounted for in their entirety as liabilities measured at their amortized cost. We elected to early adopt ASU No. 2020-06 on a modified retrospective basis beginning January 1, 2021. The adoption of this ASU increased our long-term debt and decreased the reported value of our common stock by $44.1 million and $41.5 million, respectively, as we reclassified the conversion features associated with our various outstanding convertible senior notes from equity to long-term debt. The adoption of this ASU also increased our retained earnings and decreased deferred tax liabilities by $6.7 million and $9.3 million, respectively. Subsequent to its adoption, interest expense associated with our outstanding convertible senior notes will decrease as there will no longer be debt discounts to amortize. Additionally, the ASU no longer permits the treasury stock method for convertible instruments and instead requires the application of the if-converted method to calculate the impact of our convertible senior notes on diluted earnings per share (“EPS”). We do not expect any other recently issued accounting standards to have a material impact on our financial position, results of operations or cash flows when they become effective.

Company Overview

Company Overview	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company Overview	Note 2 — Company Overview We are an international offshore energy services company that provides specialty services to the offshore energy industry, with a focus on well intervention and robotics operations. Traditionally, our services have covered the lifecycle of an offshore oil or gas field. In recent years, we have seen an increasing demand for our services from the offshore renewable energy market. We provide services primarily in deepwater in the Gulf of Mexico, Brazil, North Sea, Asia Pacific and West Africa regions. Our North Sea operations are subject to seasonal changes in demand, which generally peaks in the summer months and declines in the winter months. Our services are segregated into three reportable business segments: Well Intervention, Robotics and Production Facilities (Note 10). Our Well Intervention segment provides services enabling our customers to safely access offshore wells for the purpose of performing production enhancement or decommissioning operations. Our well intervention vessels include the Q4000 Q5000 Q7000 Seawell Well Enhancer Siem H 1 Siem Helix 2 . Our well intervention equipment includes intervention riser systems (“IRSs”), subsea intervention lubricators (“SILs”) and the Riserless Open-water Abandonment Module (“ROAM”), some of which we provide on a stand-alone basis. Our well intervention segment also includes our ownership interest in Subsea Technologies Group Limited (“STL”). Beginning in May 2019 we held a Our Robotics segment provides offshore construction, trenching, seabed clearance, inspection, repair and maintenance services to both the oil and gas and the renewable energy markets globally. Our Robotics services also complement well intervention services. Our Robotics segment includes remotely operated vehicles (“ROVs”), trenchers, a ROVDrill and two robotics support vessels under long-term charter, the Grand Canyon II Grand Canyon III Our Production Facilities segment includes the Helix Producer I HP I

Details Of Certain Accounts

Details Of Certain Accounts	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Details Of Certain Accounts	Note 3 — Details of Certain Accounts Other current assets consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Contract assets (Note 7) ​ $ 367 $ 2,446 Prepaids ​ 18,301 ​ 15,904 Deferred costs (Note 7) ​ 8,792 ​ 23,522 Income tax receivable ​ — ​ 20,787 Other receivable (Note 11) ​ 28,184 ​ 29,782 Other ​ 6,798 ​ 9,651 Total other current assets ​ $ 62,442 $ 102,092 ​ Other assets, net consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Deferred recertification and dry dock costs, net ​ $ 16,401 $ 21,464 Deferred costs (Note 7) ​ 543 ​ 861 Charter deposit (1) ​ 12,544 ​ 12,544 Intangible assets with finite lives, net ​ 3,579 ​ 3,809 Other ​ 2,184 ​ 1,335 Total other assets, net ​ $ 35,251 $ 40,013 (1) This amount is deposited with the owner of the Siem Helix 2 to offset certain payment obligations associated with the vessel at the end of the charter term. Accrued liabilities consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Accrued payroll and related benefits ​ $ 26,443 $ 24,768 Accrued interest ​ ​ 2,760 ​ ​ 7,098 Income tax payable ​ 581 ​ — Deferred revenue (Note 7) ​ 9,425 ​ 8,140 Asset retirement obligations (Note 11) ​ 29,018 ​ 30,913 Other ​ 17,013 ​ 16,116 Total accrued liabilities ​ $ 85,240 $ 87,035 ​ Other non-current liabilities consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Deferred revenue (Note 7) ​ $ 762 $ 1,869 Other ​ 719 ​ 2,009 Total other non-current liabilities ​ $ 1,481 $ 3,878 ​

Leases

Leases	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Leases	Note 4 — Leases We charter vessels and lease facilities and equipment under non-cancelable contracts that expire on various dates through 2031. We also sublease some of our facilities under non-cancelable sublease agreements. The following table details the components of our lease cost (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2021 2020 2021 2020 Operating lease cost ​ $ 14,336 ​ $ 16,132 ​ $ 45,391 $ 48,561 Variable lease cost ​ 4,298 ​ 4,204 ​ 11,417 ​ 11,256 Short-term lease cost ​ 6,258 ​ 12,923 ​ 13,233 ​ 30,089 Sublease income ​ (289) ​ (344) ​ (967) ​ (951) Net lease cost ​ $ 24,603 ​ $ 32,915 ​ $ 69,074 $ 88,955 ​ Maturities of our operating lease liabilities as of September 30, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Facilities and ​ ​ ​ Vessels Equipment Total Less than one year ​ $ 55,817 ​ $ 5,731 $ 61,548 One to two years ​ 43,045 ​ 4,946 ​ 47,991 Two to three years ​ 8,013 ​ 4,689 ​ 12,702 Three to four years ​ — ​ 3,212 ​ 3,212 Four to five years ​ — ​ 1,048 ​ 1,048 Over five years ​ — ​ 4,443 ​ 4,443 Total lease payments ​ $ 106,875 ​ $ 24,069 $ 130,944 Less: imputed interest ​ (7,388) ​ (4,082) ​ (11,470) Total operating lease liabilities ​ $ 99,487 ​ $ 19,987 $ 119,474 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current operating lease liabilities ​ $ 50,295 ​ $ 4,756 $ 55,051 Non-current operating lease liabilities ​ 49,192 ​ 15,231 ​ 64,423 Total operating lease liabilities ​ $ 99,487 ​ $ 19,987 $ 119,474 ​ Maturities of our operating lease liabilities as of December 31, 2020 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Facilities and ​ ​ ​ Vessels Equipment Total Less than one year ​ $ 54,621 ​ $ 6,028 $ 60,649 One to two years ​ 52,106 ​ 5,435 ​ 57,541 Two to three years ​ 34,580 ​ 4,649 ​ 39,229 Three to four years ​ 2,470 ​ 4,374 ​ 6,844 Four to five years ​ — ​ 2,340 ​ 2,340 Over five years ​ — ​ 4,054 ​ 4,054 Total lease payments ​ $ 143,777 ​ $ 26,880 $ 170,657 Less: imputed interest ​ (13,352) ​ (4,697) ​ (18,049) Total operating lease liabilities ​ $ 130,425 ​ $ 22,183 $ 152,608 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current operating lease liabilities ​ $ 46,748 ​ $ 4,851 $ 51,599 Non-current operating lease liabilities ​ 83,677 ​ 17,332 ​ 101,009 Total operating lease liabilities ​ $ 130,425 ​ $ 22,183 $ 152,608 ​ The following table presents the weighted average remaining lease term and discount rate: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 ​ 2020 Weighted average remaining lease term 2.6 years ​ 3.1 years Weighted average discount rate 7.59 % ​ 7.53 % ​ The following table presents other information related to our operating leases (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ ​ September 30, ​ 2021 2020 Cash paid for operating lease liabilities ​ $ 46,141 $ 49,350 Right-of-use assets obtained in exchange for new operating lease obligations ​ 5,975 ​ 36 ​

Long-Term Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Long-term Debt	Note 5 — Long-Term Debt Scheduled maturities of our long-term debt outstanding as of September 30, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2022 ​ 2023 ​ 2026 ​ MARAD ​ ​ ​ Notes Notes Notes Debt Total Less than one year ​ $ 35,000 ​ $ — ​ $ — ​ $ 7,937 $ 42,937 One to two years ​ — ​ 30,000 ​ — ​ 8,333 ​ 38,333 Two to three years ​ — ​ — ​ — ​ 8,749 ​ 8,749 Three to four years ​ — ​ — ​ — ​ 9,186 ​ 9,186 Four to five years ​ — ​ — ​ 200,000 ​ 9,644 ​ 209,644 Over five years ​ — ​ — ​ — ​ 5,001 ​ 5,001 Gross debt ​ 35,000 ​ 30,000 ​ 200,000 ​ 48,850 ​ 313,850 Unamortized debt issuance costs (1) ​ (112) ​ (359) ​ (6,203) ​ (2,683) ​ (9,357) Total debt ​ 34,888 ​ 29,641 ​ 193,797 ​ 46,167 ​ 304,493 Less current maturities ​ (34,888) ​ — ​ — ​ (7,937) ​ (42,825) Long-term debt ​ $ — ​ $ 29,641 ​ $ 193,797 ​ $ 38,230 $ 261,668 (1) Debt issuance costs are amortized to interest expense over the term of the applicable debt agreement. See Note 1 for accounting changes as a result of the adoption of ASU No. 2020-06. Below is a summary of certain components of our indebtedness: Credit Agreement On September 30, 2021, we entered into an asset-based credit agreement (the “ABL Facility”) with Bank of America, N.A. (“Bank of America”), Wells Fargo Bank, N.A. and Zions Bancorporation. The ABL Facility provides for an $80 million asset-based revolving credit facility, which matures on September 30, 2026 , with a springing maturity 91 days prior to the maturity of any outstanding indebtedness with a principal amount in excess of $50 million. The ABL Facility also permits us to request an increase of the facility by up to $70 million, subject to certain conditions. Commitments under the ABL Facility are comprised of separate U.S. and U.K. revolving credit facility commitments of $45 million and $35 million, respectively. The ABL Facility provides funding based on a borrowing base calculation that includes eligible U.S. and U.K. customer accounts receivable and cash, and provides for a $10 million sub-limit for the issuance of letters of credit. As of September 30, 2021, we had no borrowings under the ABL Facility, and our available borrowing capacity under that facility, based on the borrowing base, totaled $69.6 million, net of $2.2 million of letters of credit issued under that facility. We and certain of our U.S. and U.K. subsidiaries are the initial borrowers under the ABL Facility, whose obligations under the ABL Facility are guaranteed by those borrowers and certain other U.S. and U.K. subsidiaries, excluding Cal Dive I – Title XI, Inc. (“CDI Title XI”), Helix Offshore Services Limited and certain other enumerated subsidiaries. Other subsidiaries may be added as guarantors of the facility in the future. The ABL Facility is secured by all accounts receivable and designated deposit accounts of the U.S. borrowers and guarantors, and by substantially all of the assets of the U.K. borrowers and guarantors. U.S. borrowings under the ABL Facility initially bear interest at the LIBOR rate plus a margin of 1.50% to 2.00% or at a base rate plus a margin of 0.50% to 1.00%. U.K. borrowings under the ABL Facility denominated in U.S. dollars initially bear interest at the LIBOR rate The ABL Facility includes certain limitations on our ability to incur additional indebtedness, grant liens on assets, pay dividends and make distributions on equity interests, dispose of assets, make investments, repay certain indebtedness, engage in mergers, and other matters, in each case subject to certain exceptions. The ABL Facility contains customary default provisions which, if triggered, could result in acceleration of all amounts then outstanding. The ABL Facility requires us to satisfy and maintain a fixed charge coverage ratio of not less than 1.0 to 1.0 if availability is less than the greater of 10% of the borrowing base or $8 million. The ABL Facility also requires us to maintain a pro forma minimum excess availability of $16 million for the 91 days prior to the maturity of each of our outstanding convertible senior notes. Convertible Senior Notes Due 2022 (“2022 Notes”) The 2022 Notes bear interest at a coupon interest rate of 4.25% per annum payable semi-annually in arrears on November 1 and May 1 of each year until maturity. The 2022 Notes mature on May 1, 2022 unless earlier converted, redeemed or repurchased by us. The 2022 Notes are convertible by their holders at any time beginning February 1, 2022 at an initial conversion rate of 71.9748 shares of our common stock per $1,000 principal amount, which currently represents 2,519,118 potentially convertible shares at an initial conversion price of approximately $13.89 per share of common stock. Upon conversion, we have the right to satisfy our conversion obligation by delivering cash, shares of our common stock or any combination thereof. Prior to February 1, 2022, holders of the 2022 Notes may convert their notes if the closing price of our common stock exceeds 130% of the conversion price for at least 20 days in the period of 30 consecutive trading days ending on the last trading day of the preceding fiscal quarter (share price condition) or if the trading price of the 2022 Notes was equal to or less than 97% of the conversion value of the notes during the five consecutive business days immediately after any ten consecutive trading day period (trading price condition). Holders of the 2022 Notes may also convert their notes if we make certain distributions on shares of our common stock or engage in certain corporate transactions, in which case the holders may be entitled to an increase in the conversion rate, depending on the price of our common shares and the time remaining to maturity, of up to 30.5887 shares of our common stock per $1,000 principal amount. Prior to November 1, 2019, the 2022 Notes were not redeemable. On or after November 1, 2019, we may redeem all or any portion of the 2022 Notes if the price of our common stock has been at least 130% of the conversion price for at least 20 trading days during any 30 consecutive trading day period preceding our redemption notice. Any redemption would be payable in cash equal to 100% of the principal amount plus accrued and unpaid interest and a “make-whole premium” calculated as the present value of all remaining scheduled interest payments. Holders of the 2022 Notes may convert any of their notes if we call the notes for redemption. Holders of the 2022 Notes may also require us to repurchase the notes following a “fundamental change,” which includes a change of control or a termination of trading of our common stock (as defined in the indenture governing the 2022 Notes). The indenture governing the 2022 Notes contains customary terms and covenants, including that upon certain events of default, the entire principal amount of and any accrued interest on the notes may be declared immediately due and payable. In the case of certain events of bankruptcy, insolvency or reorganization relating to us or a subsidiary, the principal amount of the 2022 Notes together with any accrued interest will become immediately due and payable. The 2022 Notes were initially separated between the equity component recognized in shareholders’ equity and the debt component, which was presented as long-term debt, net of the unamortized debt discount and debt issuance costs. The unamortized debt discount and debt issuance costs were being accreted to interest expense through the maturity date of the 2022 Notes. As of December 31, 2020, unamortized debt discount and debt issuance costs related to the 2022 Notes totaled $1.5 million. As a result of the adoption of ASU No. 2020-06 beginning January 1, 2021, there is no longer any debt discount (or related accretion) associated with the 2022 Notes (Note 1). As of September 30, 2021, unamortized debt issuance costs related to the 2022 Notes were $0.1 million. The effective interest rate for the 2022 Notes prior to the adoption of ASU No. 2020-06 was 7.3%. The effective interest rate subsequent to the adoption of ASU No. 2020-06 decreased to 4.8%. For the three- and nine-month periods ended September 30, 2021, total interest expense related to the 2022 Notes was $0.4 million and $1.3 million, respectively, with coupon interest expense of $0.4 million and $1.1 million, respectively, and the amortization of issuance costs of $0.2 million for the nine-month period ended September 30, 2021. For the three- and nine-month periods ended September 30, 2020, total interest expense related to the 2022 Notes was $1.4 million and $6.0 million, respectively, with coupon interest expense of $0.8 million and $3.5 million, respectively, and the amortization of debt discount and issuance costs of $0.6 million and $2.5 million, respectively. Convertible Senior Notes Due 2023 (“2023 Notes”) The 2023 Notes bear interest at a coupon interest rate of 4.125% per annum payable semi-annually in arrears on March 15 and September 15 of each year until maturity. The 2023 Notes mature on September 15, 2023 unless earlier converted, redeemed or repurchased by us. The 2023 Notes are convertible by their holders at any time beginning March 15, 2023 at an initial conversion rate of 105.6133 shares of our common stock per $1,000 principal amount, which currently represents 3,168,399 potentially convertible shares at an initial conversion price of approximately $9.47 per share of common stock. Upon conversion, we have the right to satisfy our conversion obligation by delivering cash, shares of our common stock or any combination thereof. Prior to March 15, 2023, holders of the 2023 Notes may convert their notes if the closing price of our common stock exceeds 130% of the conversion price for at least 20 days in the period of 30 consecutive trading days ending on the last trading day of the preceding fiscal quarter (share price condition) or if the trading price of the 2023 Notes was equal to or less than 97% of the conversion value of the notes during the five consecutive business days immediately after any ten consecutive trading day period (trading price condition). Holders of the 2023 Notes may also convert their notes if we make certain distributions on shares of our common stock or engage in certain corporate transactions, in which case the holders may be entitled to an increase in the conversion rate, depending on the price of our common shares and the time remaining to maturity, of up to 47.5260 shares of our common stock per $1,000 principal amount. Prior to March 15, 2021, the 2023 Notes were not redeemable. On or after March 15, 2021, we may redeem all or any portion of the 2023 Notes if the price of our common stock has been at least 130% of the conversion price for at least 20 trading days during any 30 consecutive trading day period preceding our redemption notice. Any redemption would be payable in cash equal to 100% of the principal amount to be redeemed plus accrued and unpaid interest and a “make-whole premium” calculated as the present value of all remaining scheduled interest payments. Holders of the 2023 Notes may convert any of their notes if we call the notes for redemption. Holders of the 2023 Notes may also require us to repurchase the notes following a “fundamental change,” which includes a change of control or a termination of trading of our common stock (as defined in the indenture governing the 2023 Notes). The indenture governing the 2023 Notes contains customary terms and covenants, including that upon certain events of default, the entire principal amount of and any accrued interest on the notes may be declared immediately due and payable. In the case of certain events of bankruptcy, insolvency or reorganization relating to us or a significant subsidiary, the principal amount of the 2023 Notes together with any accrued interest will become immediately due and payable. The 2023 Notes were initially separated between the equity component recognized in shareholders’ equity and the debt component, which was presented as long-term debt, net of the unamortized debt discount and debt issuance costs. The unamortized debt discount and debt issuance costs were being accreted to interest expense through the maturity date of the 2023 Notes. As of December 31, 2020, unamortized debt discount and debt issuance costs related to the 2023 Notes totaled $3.1 million. As a result of the adoption of ASU No. 2020-06 beginning January 1, 2021, there is no longer any debt discount (or related accretion) associated with the 2023 Notes (Note 1). As of September 30, 2021, unamortized debt issuance costs related to the 2023 Notes were $0.4 million. The effective interest rate for the 2023 Notes prior to the adoption of ASU No. 2020-06 was 7.8%. The effective interest rate subsequent to the adoption of ASU No. 2020-06 decreased to 4.8%. For the three- and nine-month periods ended September 30, 2021, total interest expense related to the 2023 Notes was $0.3 million and $1.0 million, respectively, with coupon interest expense of $0.3 million and $0.9 million, respectively, and the amortization of issuance costs of $0.1 million for the nine-month period ended September 30, 2021. For the three- and nine-month periods ended September 30, 2020, total interest expense related to the 2023 Notes was $1.4 million and $6.0 million, respectively, with coupon interest expense of $0.8 million and $3.4 million, respectively, and the amortization of debt discount and issuance costs of $0.6 million and $2.6 million, respectively. Convertible Senior Notes Due 2026 (“2026 Notes”) The 2026 Notes bear interest at a coupon interest rate of 6.75% per annum payable semi-annually in arrears on February 15 and August 15 of each year, beginning February 15, 2021 until maturity. The 2026 Notes mature on February 15, 2026 unless earlier converted, redeemed or repurchased by us. The 2026 Notes are convertible by their holders at any time beginning November 17, 2025 at an initial conversion rate of 143.3795 shares of our common stock per $1,000 principal amount, which currently represents 28,675,900 potentially convertible shares at an initial conversion price of approximately $6.97 per share of common stock. Upon conversion, we have the right to satisfy our conversion obligation by delivering cash, shares of our common stock or any combination thereof. Prior to November 17, 2025, holders of the 2026 Notes may convert their notes if the closing price of our common stock exceeds 130% of the conversion price for at least 20 days in the period of 30 consecutive trading days ending on the last trading day of the preceding fiscal quarter (share price condition) or if the trading price of the 2026 Notes was equal to or less than 97% of the conversion value of the notes during the five consecutive business days immediately after any ten consecutive trading day period (trading price condition). Holders of the 2026 Notes may also convert their notes if we make certain distributions on shares of our common stock or engage in certain corporate transactions, in which case the holders may be entitled to an increase in the conversion rate, depending on the price of our common shares and the time remaining to maturity, of up to 64.5207 shares of our common stock per $1,000 principal amount. Prior to August 15, 2023, the 2026 Notes are not redeemable. On or after August 15, 2023, we may redeem all or any portion of the 2026 Notes if the price of our common stock has been at least 130% of the conversion price for at least 20 trading days during any 30 consecutive trading day period preceding our redemption notice. Any redemption would be payable in cash equal to 100% of the principal amount plus accrued and unpaid interest and a “make-whole premium” calculated as the present value of all remaining scheduled interest payments. Holders of the 2026 Notes may convert any of their notes if we call the notes for redemption. Holders of the 2026 Notes may also require us to repurchase the notes following a “fundamental change,” which includes a change of control or a termination of trading of our common stock (as defined in the indenture governing the 2026 Notes). The indenture governing the 2026 Notes contains customary terms and covenants, including that upon certain events of default, the entire principal amount of and any accrued interest on the notes may be declared immediately due and payable. In the case of certain events of bankruptcy, insolvency or reorganization relating to us or a significant subsidiary, the principal amount of the 2026 Notes together with any accrued interest will become immediately due and payable. The 2026 Notes were initially separated between the equity component recognized in shareholders’ equity and the debt component, which was presented as long-term debt, net of the unamortized debt discount and debt issuance costs. The unamortized debt discount and debt issuance costs were being accreted to interest expense through the maturity date of the 2026 Notes. As of December 31, 2020, unamortized debt discount and debt issuance costs related to the 2026 Notes totaled $47.3 million. As a result of the adoption of ASU No. 2020-06 beginning January 1, 2021, there is no longer any debt discount (or related accretion) associated with the 2026 Notes (Note 1). As of September 30, 2021, unamortized debt issuance costs related to the 2026 Notes were $6.2 million. The effective interest rate for the 2026 Notes prior to the adoption of ASU No. 2020-06 was 12.4%. The effective interest rate subsequent to the adoption of ASU No. 2020-06 decreased to 7.6%. For the three- and nine-month periods ended September 30, 2021, total interest expense related to the 2026 Notes was $3.7 million and $11.0 million, respectively, with coupon interest expense of $3.4 million and $10.1 million, respectively, and the amortization of debt issuance costs of $0.3 million and $0.9 million, respectively. For the three- and nine-month periods ended September 30, 2020, total interest expense related to the 2026 Notes was $2.5 million with coupon interest expense of $1.7 million and the amortization of debt discount and issuance costs of $0.8 million. 2026 Capped Calls In connection with the 2026 Notes offering, we entered into capped call transactions (the “2026 Capped Calls”) with three separate option counterparties. The 2026 Capped Calls are separate transactions from the 2026 Notes and do not change the holders' rights under the 2026 Notes. Holders of the 2026 Notes do not have any rights with respect to the 2026 Capped Calls. The 2026 Capped Calls are for an aggregate of 28,675,900 shares of our common stock, which corresponds to the shares into which the 2026 Notes are initially convertible. The capped call shares are subject to certain anti-dilution adjustments. Each capped call option has an initial strike price of approximately $6.97 per share, which corresponds to the initial conversion price of the 2026 Notes, and an initial cap price of approximately $8.42 per share. The strike and cap prices are subject to certain adjustments. The 2026 Capped Calls are intended to offset some or all of the potential dilution to Helix common shares caused by any conversion of the 2026 Notes up to the cap price. The 2026 Capped Calls can be settled in either net shares or cash at our option in components commencing December 15, 2025 and ending February 12, 2026, which could be extended under certain circumstances. The 2026 Capped Calls are subject to either adjustment or termination upon the occurrence of specified extraordinary events affecting Helix, including a merger, tender offer, nationalization, insolvency or delisting. In addition, certain events may result in a termination of the 2026 Capped Calls, including changes in law, insolvency filings and hedging disruptions. The 2026 Capped Calls are recorded at their aggregate cost of $10.6 million as a reduction to common stock in the shareholders’ equity section of our consolidated balance sheet. MARAD Debt In 2005, Helix’s subsidiary CDI – Title XI issued its U.S. Government Guaranteed Ship Financing Bonds, Q4000 Series, to refinance the construction financing originally granted in 2002 of the Q4000 Q4000 Q4000 Q4000 Other We previously had a credit agreement with a syndicated bank lending group for a term loan (the “Nordea Q5000 Loan”) to finance the construction of the Q5000 Q5000 We previously had another credit agreement (and the amendments made thereafter, collectively the “Credit Agreement”) with a group of lenders led by Bank of America. The Credit Agreement was comprised of a term loan (the “Term Loan”) and a revolving credit facility (the “Revolving Credit Facility”) with a maximum availability of $175 million and had a maturity date of December 31, 2021. Concurrent with our entering into the ABL Facility, the Credit Agreement was terminated. The $28 million remaining balance of the Term Loan was repaid in full and the letters of credit issued under the Revolving Credit Facility were transferred to the ABL Facility. We had no borrowings under the Revolving Credit Facility. In accordance with the ABL Facility, the 2022 Notes, the 2023 Notes, the 2026 Notes and the MARAD Debt, we are required to comply with certain covenants, including a springing fixed charge coverage ratio and minimum liquidity with respect to the ABL Facility and the maintenance of net worth, working capital and debt-to-equity requirements with respect to the MARAD Debt. As of September 30, 2021, we were in compliance with these covenants. The following table details the components of our net interest expense (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ 2021 2020 2021 2020 ​ Interest expense ​ $ 6,097 ​ $ 8,007 ​ $ 18,152 $ 22,580 ​ Capitalized interest ​ — ​ — ​ — ​ (1,182) ​ Interest income ​ (169) ​ (409) ​ (252) ​ (991) ​ Net interest expense ​ $ 5,928 ​ $ 7,598 ​ $ 17,900 $ 20,407 ​ ​

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Note 6 — Income Taxes We believe that our recorded deferred tax assets and liabilities are reasonable. However, tax laws and regulations are subject to interpretation, and the outcomes of tax disputes are inherently uncertain; therefore, our assessments can involve a series of complex judgments about future events and rely heavily on estimates and assumptions. The U.S. Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”), which was signed into law on March 27, 2020, is an economic stimulus package designed to aid in offsetting the economic damage caused by the ongoing COVID-19 pandemic and includes various changes to U.S. income tax regulations. The CARES Act permits the carryback of certain net operating losses, which previously had been required to be carried forward, at the tax rates applicable in the relevant carryback year. As a result of these changes, in the nine-month period ended September 30, 2020 we recognized an estimated $7.6 million net tax benefit ($18.9 million current tax benefit and $11.3 million deferred tax expense). This net tax benefit was generated as our deferred tax assets related to U.S. net operating losses were realized at higher prior year income tax rates. During the nine-month period ended September 30, 2020, we migrated two of our foreign subsidiaries into our U.S. consolidated tax group. As a result, these subsidiaries are not subject to future U.S. branch profits tax and a net deferred tax benefit of $8.3 million was recognized. The effective tax rates for the three-month periods ended September 30, 2021 and 2020 were 5.3% and 17.6%, respectively. The variance was primarily attributable to the earnings mix between our higher and lower tax rate jurisdictions as well as the impact of the CARES Act in 2020. The effective tax rates for the nine-month periods ended September 30, 2021 and 2020 were 7.5% and 9,777.0%, respectively. The effective tax rate for the nine-month period ended September 30, 2021 was lower than the U.S. statutory rate primarily driven by losses in jurisdictions with low tax rates as well as non-U.S. withholding and deemed profits taxes paid. The effective tax rate for the nine-month period ended September 30, 2020 was significantly higher than the U.S. statutory rate primarily due to the recognition of benefits from our foreign subsidiary restructuring and the CARES Act, as discussed above, in relation to nominal pre-tax losses. The primary differences between the income tax provision (benefit) at the U.S. statutory rate and our actual income tax provision (benefit) are as follows (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ Nine Months Ended ​ ​ ​ September 30, ​ ​ September 30, ​ ​ 2021 2020 ​ 2021 2020 ​ Taxes at U.S. statutory rate ​ $ (4,221) 21.0 % $ 6,232 21.0 % ​ $ (8,124) 21.0 % $ (35) 21.0 % ​ Foreign tax provision ​ 5,134 (25.5) ​ 1,088 3.7 ​ ​ 3,669 (9.5) ​ (28) 17.0 ​ ​ CARES Act ​ — — ​ (2,362) (8.0) ​ ​ — — ​ (7,596) 4,603.6 ​ ​ Subsidiary restructuring ​ — — ​ — — ​ ​ — — ​ (8,333) 5,050.3 ​ ​ Other (1) ​ (1,971) 9.8 ​ 274 0.9 ​ ​ 1,545 (4.0) ​ (140) 85.1 ​ ​ Income tax provision (benefit) ​ $ (1,058) 5.3 % $ 5,232 17.6 % ​ $ (2,910) 7.5 % $ (16,132) 9,777.0 % ​ (1) Includes interim period allocations of $(1.7) million and $1.1 million, respectively, for the three- and nine-month periods ended September 30, 2021 and $2.3 million for both the three- and nine-month periods ended September 30, 2020.

Revenue From Contracts With Cus

Revenue From Contracts With Customers	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue From Contracts With Customers	Note 7 — Revenue from Contracts with Customers Disaggregation of Revenue Our revenues are primarily derived from short-term and long-term service contracts with customers. Our service contracts generally contain either provisions for specific time, material and equipment charges that are billed in accordance with the terms of such contracts (dayrate contracts) or lump sum payment provisions (lump sum contracts). We record revenues net of taxes collected from customers and remitted to governmental authorities. Contracts are classified as long-term if all or part of the contract is to be performed over a period extending beyond 12 months from the effective date of the contract. Long-term contracts may include multi-year agreements whereby the commitment for services in any one year may be short in duration. The following table provides information about disaggregated revenue by contract duration (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Well ​ ​ ​ Production ​ Intercompany ​ Total ​ Intervention Robotics Facilities Eliminations (1) Revenue Three months ended September 30, 2021 ​ ​ ​ ​ ​ Short-term ​ $ 92,954 ​ $ 30,186 ​ $ — ​ $ — ​ $ 123,140 Long-term ​ 38,360 ​ 12,437 ​ 18,552 ​ (11,773) ​ 57,576 Total ​ $ 131,314 ​ $ 42,623 ​ $ 18,552 ​ $ (11,773) ​ $ 180,716 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, 2020 ​ ​ ​ ​ ​ Short-term ​ $ 46,907 ​ $ 28,782 ​ $ — ​ $ — ​ $ 75,689 Long-term ​ 93,896 ​ 21,020 ​ 14,167 ​ (11,282) ​ 117,801 Total ​ $ 140,803 ​ $ 49,802 ​ $ 14,167 ​ $ (11,282) ​ $ 193,490 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended September 30, 2021 ​ ​ ​ ​ ​ Short-term ​ $ 218,840 ​ $ 60,605 ​ $ — ​ $ — ​ $ 279,445 Long-term ​ 178,547 ​ 35,825 ​ 49,217 ​ (36,962) ​ 226,627 Total ​ $ 397,387 ​ $ 96,430 ​ $ 49,217 ​ $ (36,962) ​ $ 506,072 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended September 30, 2020 ​ ​ ​ ​ ​ Short-term ​ $ 184,599 ​ $ 87,307 ​ $ — ​ $ — ​ $ 271,906 Long-term ​ 242,697 ​ 48,589 ​ 43,301 ​ (32,835) ​ 301,752 Total ​ $ 427,296 ​ $ 135,896 ​ $ 43,301 ​ $ (32,835) ​ $ 573,658 (1) Intercompany revenues among our business segments are under agreements that are considered long-term. Contract Balances Accounts receivable are recognized when our right to consideration becomes unconditional. Contract assets are rights to consideration in exchange for services that we have provided to a customer when those rights are conditioned on our future performance. Contract assets generally consist of (i) demobilization fees recognized ratably over the contract term but invoiced upon completion of the demobilization activities and (ii) revenue recognized in excess of the amount billed to the customer for lump sum contracts when the cost-to-cost method of revenue recognition is utilized. Contract assets are reflected in “Other current assets” in the accompanying condensed consolidated balance sheets (Note 3). Contract assets were $0.4 million at September 30, 2021 and $2.4 million at December 31, 2020. We had no credit losses on our contract assets for the three- and nine-month periods ended September 30, 2021 and 2020. Contract liabilities are obligations to provide future services to a customer for which we have already received, or have the unconditional right to receive, the consideration for those services from the customer. Contract liabilities may consist of (i) advance payments received from customers, including upfront mobilization fees allocated to a single performance obligation and recognized ratably over the contract term and/or (ii) amounts billed to the customer in excess of revenue recognized for lump sum contracts when the cost-to-cost method of revenue recognition is utilized. Contract liabilities are reflected as “Deferred revenue,” a component of “Accrued liabilities” and “Other non-current liabilities” in the accompanying condensed consolidated balance sheets (Note 3). Contract liabilities totaled $10.2 million at September 30, 2021 and $10.0 million at December 31, 2020. Revenue recognized for the three- and nine-month periods ended September 30, 2021 included $4.0 million and $6.7 million, respectively, that were included in the contract liability balance at the beginning of each period. Revenue recognized for the three- and nine-month periods ended September 30, 2020 included $3.4 million and $8.8 million, respectively, that were included in the contract liability balance at the beginning of each period. We report the net contract asset or contract liability position on a contract-by-contract basis at the end of each reporting period. Performance Obligations As of September 30, 2021, $230.5 million related to unsatisfied performance obligations was expected to be recognized as revenue in the future, with $68.6 million in 2021 , $102.6 million in 2022 and $59.3 million in 2023 and thereafter. These amounts include fixed consideration and estimated variable consideration for both wholly and partially unsatisfied performance obligations, including mobilization and demobilization fees. These amounts are derived from the specific terms of our contracts, and the expected timing for revenue recognition is based on the estimated start date and duration of each contract according to the information known at September 30, 2021. For the three- and nine-month periods ended September 30, 2021 and 2020, revenues recognized from performance obligations satisfied (or partially satisfied) in previous periods were immaterial. Contract Fulfillment Costs Contract fulfillment costs consist of costs incurred in fulfilling a contract with a customer. Our contract fulfillment costs primarily relate to costs incurred for mobilization of personnel and equipment at the beginning of a contract and costs incurred for demobilization at the end of a contract. Mobilization costs are deferred and amortized ratably over the contract term (including anticipated contract extensions) based on the pattern of the provision of services to which the contract fulfillment costs relate. Demobilization costs are recognized when incurred at the end of the contract. Deferred contract costs are reflected as “Deferred costs,” a component of “Other current assets” and “Other assets, net” in the accompanying condensed consolidated balance sheets (Note 3). Our deferred contract costs totaled $9.3 million at September 30, 2021 and $24.4 million at December 31, 2020. For the three- and nine-month periods ended September 30, 2021, we recorded $11.7 million and $31.6 million, respectively, related to amortization of these deferred contract costs. For the three- and nine-month periods ended September 30, 2020, we recorded $9.2 million and $27.2 million, respectively, related to amortization of these deferred contract costs. There were no associated impairment losses for any period presented. For additional information regarding revenue recognition, see Notes 2 and 12 to our 2020 Form 10-K.

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Earnings Per Share	Note 8 — Earnings Per Share We have shares of restricted stock issued and outstanding that are currently unvested. Because holders of shares of unvested restricted stock are entitled to the same liquidation and dividend rights as the holders of our unrestricted common stock, we are required to compute basic and diluted EPS under the two-class method in periods in which we have earnings. Under the two-class method, net income or loss attributable to common shareholders for each period is allocated based on the participation rights of both common shareholders and the holders of any participating securities as if earnings for the respective periods had been distributed. For periods in which we have a net loss we do not use the two-class method as holders of our restricted shares are not obligated to share in such losses. Basic EPS is computed by dividing net income or loss available to common shareholders by the weighted average shares of our common stock outstanding. The calculation of diluted EPS is similar to that for basic EPS, except that the denominator includes dilutive common stock equivalents and the numerator excludes the effects of dilutive common stock equivalents, if any. The computations of the numerator (income) and denominator (shares) to derive the basic and diluted EPS amounts presented on the face of the accompanying condensed consolidated statements of operations are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Three Months Ended ​ ​ September 30, 2021 ​ September 30, 2020 ​ Income Shares Income Shares Basic: ​ ​ Net income (loss) attributable to common shareholders ​ $ (19,043) ​ ​ $ 24,499 Less: Undistributed earnings allocated to participating securities ​ — ​ ​ ​ (180) Accretion of redeemable noncontrolling interests ​ — ​ ​ ​ (128) Net income (loss) available to common shareholders, basic ​ $ (19,043) ​ 150,088 ​ $ 24,191 149,032 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted: ​ ​ ​ Net income (loss) available to common shareholders, basic ​ $ (19,043) ​ 150,088 ​ $ 24,191 149,032 Effect of dilutive securities: ​ ​ ​ Share-based awards other than participating securities ​ — ​ — ​ — 919 Undistributed earnings reallocated to participating securities ​ — ​ — ​ 2 — Net income (loss) available to common shareholders, diluted ​ $ (19,043) ​ 150,088 ​ $ 24,193 149,951 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ Nine Months Ended ​ ​ September 30, 2021 ​ September 30, 2020 ​ Income ​ Income Shares Basic: ​ ​ Net income (loss) attributable to common shareholders ​ $ (35,630) ​ ​ $ 18,011 Less: Undistributed earnings allocated to participating securities ​ — ​ ​ ​ (117) Less: Accretion of redeemable noncontrolling interests ​ (241) ​ ​ ​ (2,283) Net income (loss) available to common shareholders, basic ​ $ (35,871) ​ 150,018 ​ $ 15,611 148,956 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted: ​ ​ ​ Net income (loss) available to common shareholders, basic ​ $ (35,871) ​ 150,018 ​ $ 15,611 148,956 Effect of dilutive securities: ​ ​ ​ Share-based awards other than participating securities ​ — ​ — ​ — 868 Undistributed earnings reallocated to participating securities ​ — ​ — ​ 1 — Net income (loss) available to common shareholders, diluted ​ $ (35,871) ​ 150,018 ​ $ 15,612 149,824 ​ We had net losses for the three- and nine-month periods ended September 30, 2021. Accordingly, our diluted EPS calculation for these periods excluded any assumed exercise or conversion of common stock equivalents. These common stock equivalents were excluded because they were deemed to be anti-dilutive, meaning their inclusion would have reduced the reported net loss per share in the applicable periods. Shares that otherwise would have been included in the diluted per share calculations assuming we had earnings are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ 2021 2021 ​ Diluted shares (as reported) 150,088 150,018 ​ Share-based awards 1,384 1,306 ​ Total 151,472 151,324 ​ ​ The following potentially dilutive shares related to the 2022 Notes, the 2023 Notes and the 2026 Notes were excluded from the diluted EPS calculation as they were anti-dilutive (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ 2021 2020 2021 2020 ​ 2022 Notes 2,519 5,688 2,519 7,886 ​ 2023 Notes 3,168 8,076 3,168 11,481 ​ 2026 Notes 28,676 14,650 28,676 4,919 ​ ​

Employee Benefit Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Employee Benefit Plans	Note 9 — Employee Benefit Plans Long-Term Incentive Plan As of September 30, 2021, there were 5.9 million shares of our common stock available for issuance under our 2005 Long-Term Incentive Plan, as amended and restated (the “2005 Incentive Plan”). During the nine-month period ended September 30, 2021, the following grants of share-based awards were made under the 2005 Incentive Plan: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Grant Date ​ ​ ​ ​ ​ ​ Fair Value ​ ​ Date of Grant Shares/Units Per Share/Unit Vesting Period January 1, 2021 (1) 452,381 ​ $ 4.20 33% per year over three years January 4, 2021 (2) 452,381 ​ $ 5.33 100% on January 4, 2024 January 4, 2021 (3) 14,249 ​ $ 4.20 100% on January 1, 2023 April 1, 2021 (3) 9,282 ​ $ 5.05 100% on January 1, 2023 July 1, 2021 (3) 8,403 ​ $ 5.71 100% on January 1, 2023 July 23, 2021 (4) 14,664 ​ $ 4.54 100% on July 23, 2022 (1) Reflects grants of restricted stock units (“RSUs”) to our executive officers. (2) Reflects grants of performance share units (“PSUs”) to our executive officers. These PSUs consist of two components: (i) 50% based on the performance of our common stock and (ii) 50% based on cumulative total Free Cash Flow. The grant date fair value represents the average grant date fair value of the two components. (3) Reflects grants of restricted stock to certain independent members of our Board of Directors (our “Board”) who have elected to take their quarterly fees in stock in lieu of cash. (4) Reflects a grant of restricted stock made to a new independent member of our Board upon his joining our Board. Compensation cost for restricted stock is the product of the grant date fair value of each share and the number of shares granted and is recognized over the applicable vesting period on a straight-line basis. Forfeitures are recognized as they occur. No restricted stock awards have been granted to our executive officers or other employees in 2021. For the three- and nine-month periods ended September 30, 2021, $0.8 million and $2.5 million, respectively, were recognized as share-based compensation related to restricted stock. For the three- and nine-month periods ended September 30, 2020, $1.1 million and $3.2 million, respectively, were recognized as share-based compensation related to restricted stock. Our existing PSUs that were granted prior to 2021 are to be settled solely in shares of our common stock and are accounted for as equity awards. Those PSUs contain a service condition and a market condition. PSUs granted in 2021 may be settled in either cash or shares of our common stock upon vesting at the discretion of the Compensation Committee of our Board and are initially accounted for as equity awards. The PSUs granted in 2021 consist of two components: (i) 50% based on the performance of our common stock against peer group companies, which contains a service condition and a market condition, and (ii) 50% based on cumulative total Free Cash Flow, which contains a service condition and a performance condition. Free Cash Flow is calculated as cash flows from operating activities less capital expenditures, net of proceeds from sale of assets. Our PSUs cliff vest at the end of a three-year period with the maximum amount of the award being 200% of the original PSU awards and the minimum amount being zero. Compensation cost for PSUs that have a service condition and a market condition and are accounted for as equity awards is measured based on the grant date estimated fair value and recognized over the vesting period on a straight-line basis. The grant date estimated fair value is determined using a Monte Carlo simulation model. Compensation cost for PSUs that have a service condition and a performance condition and are accounted for as equity awards is initially measured based on the grant date fair value. Cumulative compensation cost is subsequently adjusted at the end of each reporting period to reflect the current estimation of achieving the performance condition. For the three- and nine-month periods ended September 30, 2021, $1.0 million and $3.1 million, respectively, were recognized as share-based compensation related to equity PSUs. For the three- and nine-month periods ended September 30, 2020, $1.0 million and $3.0 million, respectively, were recognized as share-based compensation related to equity PSUs. In January 2021, based on the performance of our common stock price as compared to our performance peer group over a three-year period, 368,038 equity PSUs granted in 2018 vested at 200%, representing 736,075 shares of our common stock with a total market value of $3.1 million. RSUs granted in 2021 have been accounted for as liability awards. Liability RSUs are measured at their estimated fair value at each balance sheet date, and subsequent changes in the fair value of the awards are recognized in earnings for the portion of the award for which the requisite service period has elapsed. Cumulative compensation cost for vested liability RSUs equals the actual payout value upon vesting. Compensation cost recognized for the three-month period ended September 30, 2021 was minimal. For the nine-month period ended September 30, 2021, $0.4 million was recognized as compensation cost. In 2021 and 2020, we granted fixed-value cash awards of $3.5 million and $4.7 million, respectively, to select management employees under the 2005 Incentive Plan. The value of these cash awards is recognized on a straight-line basis over a vesting period of three years . For the three- and nine-month periods ended September 30, 2021, $1.0 million and $3.0 million, respectively, were recognized as compensation cost. For the three- and nine-month periods ended September 30, 2020, $1.1 million and $3.4 million, respectively, were recognized as compensation cost. Defined Contribution Plan We sponsor a defined contribution 401(k) retirement plan. We suspended our discretionary contributions for an indefinite period beginning January 2021. Employee Stock Purchase Plan We have an employee stock purchase plan (the “ESPP”). As of September 30, 2021, 1.6 million shares were available for issuance under the ESPP. The ESPP currently has a purchase limit of 260 shares per employee per purchase period. For more information regarding our employee benefit plans, including the 2005 Incentive Plan and the ESPP, see Note 14 to our 2020 Form 10-K.

Business Segment Information

Business Segment Information	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Business Segment Information	Note 10 — Business Segment Information We have three reportable business segments: Well Intervention, Robotics and Production Facilities. Our U.S., U.K. and Brazil well intervention operating segments are aggregated into the Well Intervention segment for financial reporting purposes. Our Well Intervention segment provides services enabling our customers to safely access offshore wells for the purpose of performing production enhancement or decommissioning operations primarily in the Gulf of Mexico, Brazil, the North Sea and West Africa. Our well intervention vessels include the Q4000 Q5000 Q7000 Seawell Well Enhancer Siem Helix 1 Siem Helix 2 Grand Canyon II Grand Canyon III HP I We evaluate our performance based on operating income of each reportable segment. Certain financial data by reportable segment are summarized as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ ​ 2021 2020 ​ 2021 2020 ​ Net revenues — ​ ​ ​ ​ ​ ​ Well Intervention $ 131,314 ​ $ 140,803 ​ $ 397,387 ​ $ 427,296 ​ Robotics 42,623 ​ 49,802 ​ 96,430 ​ 135,896 ​ Production Facilities 18,552 ​ 14,167 ​ 49,217 ​ 43,301 ​ Intercompany eliminations (11,773) ​ (11,282) ​ (36,962) ​ (32,835) ​ Total $ 180,716 ​ $ 193,490 ​ $ 506,072 ​ $ 573,658 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income (loss) from operations — ​ ​ ​ ​ Well Intervention $ (13,343) ​ $ 18,844 ​ $ (14,819) ​ $ 24,910 ​ Robotics 4,936 ​ 6,983 ​ 2,257 ​ 11,940 ​ Production Facilities 5,089 ​ 4,134 ​ 16,285 ​ 11,142 ​ Segment operating income (loss) (3,318) ​ 29,961 ​ 3,723 ​ 47,992 ​ Goodwill impairment (1) — ​ — ​ — ​ (6,689) ​ Corporate, eliminations and other (7,013) ​ (10,946) ​ (25,550) ​ (29,121) ​ Total $ (10,331) ​ $ 19,015 ​ $ (21,827) ​ $ 12,182 ​ (1) As a result of the decline in oil prices as well as energy and energy services valuations during the first quarter 2020 due to the COVID-19 pandemic and the price war among members of the Organization of Petroleum Exporting Countries (“OPEC”) and other non-OPEC producer nations (collectively with OPEC members, “OPEC+”), we impaired all of our goodwill, which consisted entirely of goodwill attributable to the acquisition of a controlling interest in STL. Intercompany segment amounts are derived primarily from equipment and services provided to other business segments. Intercompany segment revenues are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ 2021 2020 2021 2020 ​ Well Intervention ​ $ 4,267 ​ $ 4,120 ​ $ 17,060 ​ $ 11,334 ​ Robotics ​ 7,506 ​ 7,162 ​ 19,902 ​ 21,501 ​ Total ​ $ 11,773 ​ $ 11,282 ​ $ 36,962 ​ $ 32,835 ​ ​ Segment assets are comprised of all assets attributable to each reportable segment. Corporate and other includes all assets not directly identifiable with our business segments, most notably the majority of our cash and cash equivalents. The following table reflects total assets by reportable segment (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Well Intervention ​ $ 2,042,180 ​ $ 2,134,081 Robotics ​ 109,450 ​ 132,550 Production Facilities ​ 121,258 ​ 129,773 Corporate and other ​ 74,411 ​ 101,874 Total ​ $ 2,347,299 ​ $ 2,498,278 ​

Asset Retirement Obligations

Asset Retirement Obligations	9 Months Ended
	Sep. 30, 2021
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	Note 11 — Asset Retirement Obligations Asset retirement obligations (“AROs”) are recorded at fair value and consist of estimated costs for subsea infrastructure plug and abandonment (“P&A”) activities associated with our oil and gas properties. The estimated costs are discounted to present value using a credit-adjusted risk-free discount rate. After its initial recognition, an ARO liability is increased for the passage of time as accretion expense, which is a component of our depreciation and amortization expense. An ARO liability may also change based on revisions in estimated costs and/or timing to settle the obligations. Our AROs relate to our Droshky oil and gas properties that we acquired from Marathon Oil Corporation (“Marathon Oil”) in January 2019. In connection with assuming the P&A obligations related to those assets, we are entitled to receive agreed-upon amounts from Marathon Oil as the P&A work is completed. The following table describes the changes in our AROs (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 AROs at January 1, ​ $ 30,913 ​ $ 28,258 Revisions in estimates ​ (2,631) ​ — Accretion expense ​ 736 ​ 2,021 AROs at September 30, ​ $ 29,018 ​ $ 30,279 ​

Commitments And Contingencies A

Commitments And Contingencies And Other Matters	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies And Other Matters	Note 12 — Commitments and Contingencies and Other Matters Commitments We have long-term charter agreements with Siem Offshore AS (“Siem”) for the Siem Helix 1 Siem Helix 2 Siem Helix 1 Siem Helix 2 Grand Canyon II Grand Canyon III Grand Canyon II Grand Canyon III Contingencies and Claims We believe that there are currently no contingencies that would have a material adverse effect on our financial position, results of operations or cash flows. Litigation We are involved in various legal proceedings, some involving claims for personal injury under the General Maritime Laws of the United States and the Jones Act. In addition, from time to time we receive other claims, such as contract and employment-related disputes, in the normal course of business. We are currently involved in several lawsuits filed by current and former offshore employees seeking overtime compensation. These suits are brought as collective actions and are in various stages of litigation. In one such lawsuit, during the third quarter 2021 the United States Court of Appeals for the Fifth Circuit issued a ruling adverse to us that may also have implications for some of the other cases in which we are involved, as well as the way offshore personnel are compensated throughout our industry. We intend to further appeal this matter and to continue vigorously defending these lawsuits. Notwithstanding that we believe we retain valid defenses, at this time we have established a liability for probable losses in certain of these matters. The final outcome of these matters remains uncertain and the ultimate liability to us could be more or less than the liability established.

Statement Of Cash Flow Informat

Statement Of Cash Flow Information	9 Months Ended
	Sep. 30, 2021
Supplemental Cash Flow Information [Abstract]
Statement Of Cash Flow Information	Note 13 — Statement of Cash Flow Information We define cash and cash equivalents as cash and all highly liquid financial instruments with original maturities of three months or less. We classify cash as restricted when there are legal or contractual restrictions for its withdrawal. The following table provides supplemental cash flow information (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ ​ September 30, ​ 2021 2020 Interest paid, net of interest capitalized ​ $ 19,945 ​ $ 14,255 Income taxes paid (1) ​ 6,771 ​ 6,436 (1) Exclusive of income tax refunds. During the nine-month period ended September 30, 2021, we received $18.9 million in refunds related to the CARES Act. Our capital additions include the acquisition of property and equipment for which payment has not been made. These non-cash capital additions totaled $0.3 million at September 30, 2021 and $1.6 million at December 31, 2020.

Allowance For Credit Losses

Allowance For Credit Losses	9 Months Ended
	Sep. 30, 2021
Credit Loss [Abstract]
Allowance For Credit Losses	Note 14 — Allowance for Credit Losses We estimate current expected credit losses on our accounts receivable at each reporting date. We estimate current expected credit losses based on our credit loss history, adjusted for current factors including global economic and business conditions, offshore energy industry and market conditions, customer mix, contract payment terms and past due accounts receivable. The following table sets forth the activity in our allowance for credit losses (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 Balance at January 1, ​ $ 3,469 ​ $ — Additions (reductions) (1) ​ (213) ​ 2,387 Write-offs (2) ​ ​ (1,846) ​ ​ — Adjustments (3) ​ — ​ 785 Balance at September 30, ​ $ 1,410 ​ $ 3,172 (1) Additions (reductions) in allowance for credit losses reflect credit loss reserves (releases) during the respective periods, including a $1.7 million credit loss reserve in 2020 related to a receivable in our Robotics segment. (2) The write-offs of allowance for credit losses reflect certain receivables related to our Robotics segment that were previously reserved and subsequently deemed to be uncollectible. (3) The adjustment in allowance for credit losses reflects provision for current expected credit losses upon the adoption of ASU No. 2016-13 on January 1, 2020.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 15 — Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value accounting rules establish a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: ● Level 1. Observable inputs such as quoted prices in active markets; ● Level 2. Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and ● Level 3. Unobservable inputs for which there is little or no market data, which require the reporting entity to develop its own assumptions. Assets and liabilities measured at fair value are based on one or more of three valuation approaches as follows: (a) Market Approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities. (b) Cost Approach. Amount that would be required to replace the service capacity of an asset (replacement cost). (c) Income Approach. Techniques to convert expected future cash flows to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models). Our financial instruments include cash and cash equivalents, receivables, accounts payable and long-term debt. The carrying amount of cash and cash equivalents, trade and other current receivables as well as accounts payable approximates fair value due to the short-term nature of these instruments. The principal amount and estimated fair value of our long-term debt are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2021 ​ December 31, 2020 ​ ​ Principal ​ Fair ​ Principal ​ Fair ​ Amount (1) Value (2) (3) Amount (1) Value (2) (3) Term Loan (repaid September 2021) (4) ​ $ — ​ $ — ​ $ 29,750 ​ $ 28,969 Nordea Q5000 Loan (matured January 2021) (5) ​ — ​ — ​ 53,572 ​ 53,598 MARAD Debt (matures February 2027) ​ 48,850 ​ 53,115 ​ 56,410 ​ 62,318 2022 Notes (mature May 2022) ​ 35,000 ​ 34,638 ​ 35,000 ​ 33,513 2023 Notes (mature September 2023) ​ 30,000 ​ 29,001 ​ 30,000 ​ 28,650 2026 Notes (mature February 2026) ​ 200,000 ​ 210,143 ​ 200,000 ​ 211,383 Total debt ​ $ 313,850 ​ $ 326,897 ​ $ 404,732 ​ $ 418,431 (1) Principal amount includes current maturities and excludes any related unamortized debt discount and debt issuance costs. See Note 5 for additional disclosures on our long-term debt. (2) The estimated fair value of the 2022 Notes, the 2023 Notes and the 2026 Notes was determined using Level 1 fair value inputs under the market approach. The fair value of the Term Loan, the Nordea Q5000 Loan and the MARAD Debt was estimated using Level 2 fair value inputs under the market approach, which was determined using a third-party evaluation of the remaining average life and outstanding principal balance of the indebtedness as compared to other obligations in the marketplace with similar terms. (3) The principal amount and estimated fair value of the 2022 Notes, the 2023 Notes and the 2026 Notes are for the entire instrument inclusive of the conversion feature, which had been accounted for in shareholders’ equity through December 31, 2020. (4) The Term Loan was fully repaid in September 2021 concurrent with our entering into the ABL Facility (Note 5). (5) The Nordea Q5000 Loan was fully repaid upon maturity in January 2021 (Note 5) .

Basis Of Presentation And New_2

Basis Of Presentation And New Accounting Standards (Policies)	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis Of Presentation	The accompanying condensed consolidated financial statements include the accounts of Helix Energy Solutions Group, Inc. and its subsidiaries (collectively, “Helix”). Unless the context indicates otherwise, the terms “we,” “us” and “our” in this report refer collectively to Helix and its subsidiaries. All material intercompany accounts and transactions have been eliminated. These unaudited condensed consolidated financial statements have been prepared pursuant to instructions for the Quarterly Report on Form 10-Q required to be filed with the Securities and Exchange Commission (the “SEC”) and do not include all information and footnotes normally included in annual financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The accompanying condensed consolidated financial statements have been prepared in conformity with GAAP in U.S. dollars and are consistent in all material respects with those applied in our 2020 Annual Report on Form 10-K (our “2020 Form 10-K”) with the exception of the impact of early adopting Accounting Standards Update (“ASU”) No. 2020-06 on a modified retrospective basis beginning January 1, 2021 (see below). The preparation of these financial statements requires us to make estimates and judgments that affect the amounts reported in the financial statements and the related disclosures. Actual results may differ from our estimates. We have made all adjustments, which, unless otherwise disclosed, are of normal recurring nature, that we believe are necessary for a fair presentation of the condensed consolidated balance sheets, statements of operations, statements of comprehensive income, statements of shareholders’ equity and statements of cash flows, as applicable. The operating results for the three- and nine-month periods ended September 30, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021. Our balance sheet as of December 31, 2020 included herein has been derived from the audited balance sheet as of December 31, 2020 included in our 2020 Form 10-K. These unaudited condensed consolidated financial statements should be read in conjunction with the audited annual consolidated financial statements and notes thereto included in our 2020 Form 10-K.
Reclassifications	Certain reclassifications were made to previously reported amounts in the consolidated financial statements and notes thereto to make them consistent with the current presentation format.
New Accounting Standards	New accounting standards In August 2020, the Financial Accounting Standards Board issued ASU No. 2020-06, “Accounting for Convertible Instruments and Contracts in an Entity's Own Equity,” which simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts in an entity’s own equity. Among other changes, this ASU removes from GAAP the requirement to separate certain convertible instruments, such as our Convertible Senior Notes Due 2022, Convertible Senior Notes Due 2023 and Convertible Senior Notes Due 2026 (Note 5), into liability and equity components. Consequently, those convertible instruments will be accounted for in their entirety as liabilities measured at their amortized cost. We elected to early adopt ASU No. 2020-06 on a modified retrospective basis beginning January 1, 2021. The adoption of this ASU increased our long-term debt and decreased the reported value of our common stock by $44.1 million and $41.5 million, respectively, as we reclassified the conversion features associated with our various outstanding convertible senior notes from equity to long-term debt. The adoption of this ASU also increased our retained earnings and decreased deferred tax liabilities by $6.7 million and $9.3 million, respectively. Subsequent to its adoption, interest expense associated with our outstanding convertible senior notes will decrease as there will no longer be debt discounts to amortize. Additionally, the ASU no longer permits the treasury stock method for convertible instruments and instead requires the application of the if-converted method to calculate the impact of our convertible senior notes on diluted earnings per share (“EPS”). We do not expect any other recently issued accounting standards to have a material impact on our financial position, results of operations or cash flows when they become effective.

Details Of Certain Accounts (Ta

Details Of Certain Accounts (Tables)	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of other current assets	Other current assets consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Contract assets (Note 7) ​ $ 367 $ 2,446 Prepaids ​ 18,301 ​ 15,904 Deferred costs (Note 7) ​ 8,792 ​ 23,522 Income tax receivable ​ — ​ 20,787 Other receivable (Note 11) ​ 28,184 ​ 29,782 Other ​ 6,798 ​ 9,651 Total other current assets ​ $ 62,442 $ 102,092
Schedule of other assets, net	Other assets, net consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Deferred recertification and dry dock costs, net ​ $ 16,401 $ 21,464 Deferred costs (Note 7) ​ 543 ​ 861 Charter deposit (1) ​ 12,544 ​ 12,544 Intangible assets with finite lives, net ​ 3,579 ​ 3,809 Other ​ 2,184 ​ 1,335 Total other assets, net ​ $ 35,251 $ 40,013 (1) This amount is deposited with the owner of the Siem Helix 2 to offset certain payment obligations associated with the vessel at the end of the charter term.
Schedule of accrued liabilities	Accrued liabilities consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Accrued payroll and related benefits ​ $ 26,443 $ 24,768 Accrued interest ​ ​ 2,760 ​ ​ 7,098 Income tax payable ​ 581 ​ — Deferred revenue (Note 7) ​ 9,425 ​ 8,140 Asset retirement obligations (Note 11) ​ 29,018 ​ 30,913 Other ​ 17,013 ​ 16,116 Total accrued liabilities ​ $ 85,240 $ 87,035
Schedule of other non-current liabilities	Other non-current liabilities consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Deferred revenue (Note 7) ​ $ 762 $ 1,869 Other ​ 719 ​ 2,009 Total other non-current liabilities ​ $ 1,481 $ 3,878

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Schedule of components of lease cost	The following table details the components of our lease cost (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2021 2020 2021 2020 Operating lease cost ​ $ 14,336 ​ $ 16,132 ​ $ 45,391 $ 48,561 Variable lease cost ​ 4,298 ​ 4,204 ​ 11,417 ​ 11,256 Short-term lease cost ​ 6,258 ​ 12,923 ​ 13,233 ​ 30,089 Sublease income ​ (289) ​ (344) ​ (967) ​ (951) Net lease cost ​ $ 24,603 ​ $ 32,915 ​ $ 69,074 $ 88,955
Schedule of maturities of operating lease liabilities	Maturities of our operating lease liabilities as of September 30, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Facilities and ​ ​ ​ Vessels Equipment Total Less than one year ​ $ 55,817 ​ $ 5,731 $ 61,548 One to two years ​ 43,045 ​ 4,946 ​ 47,991 Two to three years ​ 8,013 ​ 4,689 ​ 12,702 Three to four years ​ — ​ 3,212 ​ 3,212 Four to five years ​ — ​ 1,048 ​ 1,048 Over five years ​ — ​ 4,443 ​ 4,443 Total lease payments ​ $ 106,875 ​ $ 24,069 $ 130,944 Less: imputed interest ​ (7,388) ​ (4,082) ​ (11,470) Total operating lease liabilities ​ $ 99,487 ​ $ 19,987 $ 119,474 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current operating lease liabilities ​ $ 50,295 ​ $ 4,756 $ 55,051 Non-current operating lease liabilities ​ 49,192 ​ 15,231 ​ 64,423 Total operating lease liabilities ​ $ 99,487 ​ $ 19,987 $ 119,474 ​ Maturities of our operating lease liabilities as of December 31, 2020 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Facilities and ​ ​ ​ Vessels Equipment Total Less than one year ​ $ 54,621 ​ $ 6,028 $ 60,649 One to two years ​ 52,106 ​ 5,435 ​ 57,541 Two to three years ​ 34,580 ​ 4,649 ​ 39,229 Three to four years ​ 2,470 ​ 4,374 ​ 6,844 Four to five years ​ — ​ 2,340 ​ 2,340 Over five years ​ — ​ 4,054 ​ 4,054 Total lease payments ​ $ 143,777 ​ $ 26,880 $ 170,657 Less: imputed interest ​ (13,352) ​ (4,697) ​ (18,049) Total operating lease liabilities ​ $ 130,425 ​ $ 22,183 $ 152,608 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current operating lease liabilities ​ $ 46,748 ​ $ 4,851 $ 51,599 Non-current operating lease liabilities ​ 83,677 ​ 17,332 ​ 101,009 Total operating lease liabilities ​ $ 130,425 ​ $ 22,183 $ 152,608
Schedule of weighted average remaining lease term and discount rate	The following table presents the weighted average remaining lease term and discount rate: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 ​ 2020 Weighted average remaining lease term 2.6 years ​ 3.1 years Weighted average discount rate 7.59 % ​ 7.53 %
Schedule of other information related to operating leases	The following table presents other information related to our operating leases (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ ​ September 30, ​ 2021 2020 Cash paid for operating lease liabilities ​ $ 46,141 $ 49,350 Right-of-use assets obtained in exchange for new operating lease obligations ​ 5,975 ​ 36

Long-Term Debt (Tables)

Long-Term Debt (Tables)	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Schedule of maturities of long-term debt outstanding	Scheduled maturities of our long-term debt outstanding as of September 30, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2022 ​ 2023 ​ 2026 ​ MARAD ​ ​ ​ Notes Notes Notes Debt Total Less than one year ​ $ 35,000 ​ $ — ​ $ — ​ $ 7,937 $ 42,937 One to two years ​ — ​ 30,000 ​ — ​ 8,333 ​ 38,333 Two to three years ​ — ​ — ​ — ​ 8,749 ​ 8,749 Three to four years ​ — ​ — ​ — ​ 9,186 ​ 9,186 Four to five years ​ — ​ — ​ 200,000 ​ 9,644 ​ 209,644 Over five years ​ — ​ — ​ — ​ 5,001 ​ 5,001 Gross debt ​ 35,000 ​ 30,000 ​ 200,000 ​ 48,850 ​ 313,850 Unamortized debt issuance costs (1) ​ (112) ​ (359) ​ (6,203) ​ (2,683) ​ (9,357) Total debt ​ 34,888 ​ 29,641 ​ 193,797 ​ 46,167 ​ 304,493 Less current maturities ​ (34,888) ​ — ​ — ​ (7,937) ​ (42,825) Long-term debt ​ $ — ​ $ 29,641 ​ $ 193,797 ​ $ 38,230 $ 261,668 (1) Debt issuance costs are amortized to interest expense over the term of the applicable debt agreement. See Note 1 for accounting changes as a result of the adoption of ASU No. 2020-06.
Schedule of components of net interest expense	The following table details the components of our net interest expense (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ 2021 2020 2021 2020 ​ Interest expense ​ $ 6,097 ​ $ 8,007 ​ $ 18,152 $ 22,580 ​ Capitalized interest ​ — ​ — ​ — ​ (1,182) ​ Interest income ​ (169) ​ (409) ​ (252) ​ (991) ​ Net interest expense ​ $ 5,928 ​ $ 7,598 ​ $ 17,900 $ 20,407 ​

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Schedule of differences between income tax provision (benefit) at U.S. statutory rate and actual income tax provision (benefit)	The primary differences between the income tax provision (benefit) at the U.S. statutory rate and our actual income tax provision (benefit) are as follows (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ Nine Months Ended ​ ​ ​ September 30, ​ ​ September 30, ​ ​ 2021 2020 ​ 2021 2020 ​ Taxes at U.S. statutory rate ​ $ (4,221) 21.0 % $ 6,232 21.0 % ​ $ (8,124) 21.0 % $ (35) 21.0 % ​ Foreign tax provision ​ 5,134 (25.5) ​ 1,088 3.7 ​ ​ 3,669 (9.5) ​ (28) 17.0 ​ ​ CARES Act ​ — — ​ (2,362) (8.0) ​ ​ — — ​ (7,596) 4,603.6 ​ ​ Subsidiary restructuring ​ — — ​ — — ​ ​ — — ​ (8,333) 5,050.3 ​ ​ Other (1) ​ (1,971) 9.8 ​ 274 0.9 ​ ​ 1,545 (4.0) ​ (140) 85.1 ​ ​ Income tax provision (benefit) ​ $ (1,058) 5.3 % $ 5,232 17.6 % ​ $ (2,910) 7.5 % $ (16,132) 9,777.0 % ​ (1) Includes interim period allocations of $(1.7) million and $1.1 million, respectively, for the three- and nine-month periods ended September 30, 2021 and $2.3 million for both the three- and nine-month periods ended September 30, 2020.

Revenue From Contracts With C_2

Revenue From Contracts With Customers (Tables)	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Schedule of disaggregation of revenue	The following table provides information about disaggregated revenue by contract duration (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Well ​ ​ ​ Production ​ Intercompany ​ Total ​ Intervention Robotics Facilities Eliminations (1) Revenue Three months ended September 30, 2021 ​ ​ ​ ​ ​ Short-term ​ $ 92,954 ​ $ 30,186 ​ $ — ​ $ — ​ $ 123,140 Long-term ​ 38,360 ​ 12,437 ​ 18,552 ​ (11,773) ​ 57,576 Total ​ $ 131,314 ​ $ 42,623 ​ $ 18,552 ​ $ (11,773) ​ $ 180,716 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, 2020 ​ ​ ​ ​ ​ Short-term ​ $ 46,907 ​ $ 28,782 ​ $ — ​ $ — ​ $ 75,689 Long-term ​ 93,896 ​ 21,020 ​ 14,167 ​ (11,282) ​ 117,801 Total ​ $ 140,803 ​ $ 49,802 ​ $ 14,167 ​ $ (11,282) ​ $ 193,490 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended September 30, 2021 ​ ​ ​ ​ ​ Short-term ​ $ 218,840 ​ $ 60,605 ​ $ — ​ $ — ​ $ 279,445 Long-term ​ 178,547 ​ 35,825 ​ 49,217 ​ (36,962) ​ 226,627 Total ​ $ 397,387 ​ $ 96,430 ​ $ 49,217 ​ $ (36,962) ​ $ 506,072 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended September 30, 2020 ​ ​ ​ ​ ​ Short-term ​ $ 184,599 ​ $ 87,307 ​ $ — ​ $ — ​ $ 271,906 Long-term ​ 242,697 ​ 48,589 ​ 43,301 ​ (32,835) ​ 301,752 Total ​ $ 427,296 ​ $ 135,896 ​ $ 43,301 ​ $ (32,835) ​ $ 573,658 (1) Intercompany revenues among our business segments are under agreements that are considered long-term.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Schedule of computations of basic and diluted EPS	The computations of the numerator (income) and denominator (shares) to derive the basic and diluted EPS amounts presented on the face of the accompanying condensed consolidated statements of operations are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Three Months Ended ​ ​ September 30, 2021 ​ September 30, 2020 ​ Income Shares Income Shares Basic: ​ ​ Net income (loss) attributable to common shareholders ​ $ (19,043) ​ ​ $ 24,499 Less: Undistributed earnings allocated to participating securities ​ — ​ ​ ​ (180) Accretion of redeemable noncontrolling interests ​ — ​ ​ ​ (128) Net income (loss) available to common shareholders, basic ​ $ (19,043) ​ 150,088 ​ $ 24,191 149,032 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted: ​ ​ ​ Net income (loss) available to common shareholders, basic ​ $ (19,043) ​ 150,088 ​ $ 24,191 149,032 Effect of dilutive securities: ​ ​ ​ Share-based awards other than participating securities ​ — ​ — ​ — 919 Undistributed earnings reallocated to participating securities ​ — ​ — ​ 2 — Net income (loss) available to common shareholders, diluted ​ $ (19,043) ​ 150,088 ​ $ 24,193 149,951 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ Nine Months Ended ​ ​ September 30, 2021 ​ September 30, 2020 ​ Income ​ Income Shares Basic: ​ ​ Net income (loss) attributable to common shareholders ​ $ (35,630) ​ ​ $ 18,011 Less: Undistributed earnings allocated to participating securities ​ — ​ ​ ​ (117) Less: Accretion of redeemable noncontrolling interests ​ (241) ​ ​ ​ (2,283) Net income (loss) available to common shareholders, basic ​ $ (35,871) ​ 150,018 ​ $ 15,611 148,956 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted: ​ ​ ​ Net income (loss) available to common shareholders, basic ​ $ (35,871) ​ 150,018 ​ $ 15,611 148,956 Effect of dilutive securities: ​ ​ ​ Share-based awards other than participating securities ​ — ​ — ​ — 868 Undistributed earnings reallocated to participating securities ​ — ​ — ​ 1 — Net income (loss) available to common shareholders, diluted ​ $ (35,871) ​ 150,018 ​ $ 15,612 149,824
Schedule of shares excluded from diluted EPS calculation	Shares that otherwise would have been included in the diluted per share calculations assuming we had earnings are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ 2021 2021 ​ Diluted shares (as reported) 150,088 150,018 ​ Share-based awards 1,384 1,306 ​ Total 151,472 151,324 ​ ​ The following potentially dilutive shares related to the 2022 Notes, the 2023 Notes and the 2026 Notes were excluded from the diluted EPS calculation as they were anti-dilutive (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ 2021 2020 2021 2020 ​ 2022 Notes 2,519 5,688 2,519 7,886 ​ 2023 Notes 3,168 8,076 3,168 11,481 ​ 2026 Notes 28,676 14,650 28,676 4,919 ​

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Schedule of grants of share-based awards	During the nine-month period ended September 30, 2021, the following grants of share-based awards were made under the 2005 Incentive Plan: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Grant Date ​ ​ ​ ​ ​ ​ Fair Value ​ ​ Date of Grant Shares/Units Per Share/Unit Vesting Period January 1, 2021 (1) 452,381 ​ $ 4.20 33% per year over three years January 4, 2021 (2) 452,381 ​ $ 5.33 100% on January 4, 2024 January 4, 2021 (3) 14,249 ​ $ 4.20 100% on January 1, 2023 April 1, 2021 (3) 9,282 ​ $ 5.05 100% on January 1, 2023 July 1, 2021 (3) 8,403 ​ $ 5.71 100% on January 1, 2023 July 23, 2021 (4) 14,664 ​ $ 4.54 100% on July 23, 2022 (1) Reflects grants of restricted stock units (“RSUs”) to our executive officers. (2) Reflects grants of performance share units (“PSUs”) to our executive officers. These PSUs consist of two components: (i) 50% based on the performance of our common stock and (ii) 50% based on cumulative total Free Cash Flow. The grant date fair value represents the average grant date fair value of the two components. (3) Reflects grants of restricted stock to certain independent members of our Board of Directors (our “Board”) who have elected to take their quarterly fees in stock in lieu of cash. (4) Reflects a grant of restricted stock made to a new independent member of our Board upon his joining our Board.

Business Segment Information (T

Business Segment Information (Tables)	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Schedule of financial data by reportable segment	Certain financial data by reportable segment are summarized as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ ​ 2021 2020 ​ 2021 2020 ​ Net revenues — ​ ​ ​ ​ ​ ​ Well Intervention $ 131,314 ​ $ 140,803 ​ $ 397,387 ​ $ 427,296 ​ Robotics 42,623 ​ 49,802 ​ 96,430 ​ 135,896 ​ Production Facilities 18,552 ​ 14,167 ​ 49,217 ​ 43,301 ​ Intercompany eliminations (11,773) ​ (11,282) ​ (36,962) ​ (32,835) ​ Total $ 180,716 ​ $ 193,490 ​ $ 506,072 ​ $ 573,658 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income (loss) from operations — ​ ​ ​ ​ Well Intervention $ (13,343) ​ $ 18,844 ​ $ (14,819) ​ $ 24,910 ​ Robotics 4,936 ​ 6,983 ​ 2,257 ​ 11,940 ​ Production Facilities 5,089 ​ 4,134 ​ 16,285 ​ 11,142 ​ Segment operating income (loss) (3,318) ​ 29,961 ​ 3,723 ​ 47,992 ​ Goodwill impairment (1) — ​ — ​ — ​ (6,689) ​ Corporate, eliminations and other (7,013) ​ (10,946) ​ (25,550) ​ (29,121) ​ Total $ (10,331) ​ $ 19,015 ​ $ (21,827) ​ $ 12,182 ​ (1) As a result of the decline in oil prices as well as energy and energy services valuations during the first quarter 2020 due to the COVID-19 pandemic and the price war among members of the Organization of Petroleum Exporting Countries (“OPEC”) and other non-OPEC producer nations (collectively with OPEC members, “OPEC+”), we impaired all of our goodwill, which consisted entirely of goodwill attributable to the acquisition of a controlling interest in STL.
Schedule of intercompany segment revenues	Intercompany segment revenues are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ 2021 2020 2021 2020 ​ Well Intervention ​ $ 4,267 ​ $ 4,120 ​ $ 17,060 ​ $ 11,334 ​ Robotics ​ 7,506 ​ 7,162 ​ 19,902 ​ 21,501 ​ Total ​ $ 11,773 ​ $ 11,282 ​ $ 36,962 ​ $ 32,835 ​
Schedule of total assets by reportable segment	The following table reflects total assets by reportable segment (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Well Intervention ​ $ 2,042,180 ​ $ 2,134,081 Robotics ​ 109,450 ​ 132,550 Production Facilities ​ 121,258 ​ 129,773 Corporate and other ​ 74,411 ​ 101,874 Total ​ $ 2,347,299 ​ $ 2,498,278

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	9 Months Ended
	Sep. 30, 2021
Asset Retirement Obligation Disclosure [Abstract]
Schedule of asset retirement obligations	The following table describes the changes in our AROs (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 AROs at January 1, ​ $ 30,913 ​ $ 28,258 Revisions in estimates ​ (2,631) ​ — Accretion expense ​ 736 ​ 2,021 AROs at September 30, ​ $ 29,018 ​ $ 30,279

Statement Of Cash Flow Inform_2

Statement Of Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2021
Supplemental Cash Flow Information [Abstract]
Schedule of supplemental cash flow information	The following table provides supplemental cash flow information (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ ​ September 30, ​ 2021 2020 Interest paid, net of interest capitalized ​ $ 19,945 ​ $ 14,255 Income taxes paid (1) ​ 6,771 ​ 6,436 (1) Exclusive of income tax refunds. During the nine-month period ended September 30, 2021, we received $18.9 million in refunds related to the CARES Act.

Allowance For Credit Losses (Ta

Allowance For Credit Losses (Tables)	9 Months Ended
	Sep. 30, 2021
Credit Loss [Abstract]
Schedule of activities in allowance for credit losses	The following table sets forth the activity in our allowance for credit losses (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 Balance at January 1, ​ $ 3,469 ​ $ — Additions (reductions) (1) ​ (213) ​ 2,387 Write-offs (2) ​ ​ (1,846) ​ ​ — Adjustments (3) ​ — ​ 785 Balance at September 30, ​ $ 1,410 ​ $ 3,172 (1) Additions (reductions) in allowance for credit losses reflect credit loss reserves (releases) during the respective periods, including a $1.7 million credit loss reserve in 2020 related to a receivable in our Robotics segment. (2) The write-offs of allowance for credit losses reflect certain receivables related to our Robotics segment that were previously reserved and subsequently deemed to be uncollectible. (3) The adjustment in allowance for credit losses reflects provision for current expected credit losses upon the adoption of ASU No. 2016-13 on January 1, 2020.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of principal amount and estimated fair value of long-term debt	The principal amount and estimated fair value of our long-term debt are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2021 ​ December 31, 2020 ​ ​ Principal ​ Fair ​ Principal ​ Fair ​ Amount (1) Value (2) (3) Amount (1) Value (2) (3) Term Loan (repaid September 2021) (4) ​ $ — ​ $ — ​ $ 29,750 ​ $ 28,969 Nordea Q5000 Loan (matured January 2021) (5) ​ — ​ — ​ 53,572 ​ 53,598 MARAD Debt (matures February 2027) ​ 48,850 ​ 53,115 ​ 56,410 ​ 62,318 2022 Notes (mature May 2022) ​ 35,000 ​ 34,638 ​ 35,000 ​ 33,513 2023 Notes (mature September 2023) ​ 30,000 ​ 29,001 ​ 30,000 ​ 28,650 2026 Notes (mature February 2026) ​ 200,000 ​ 210,143 ​ 200,000 ​ 211,383 Total debt ​ $ 313,850 ​ $ 326,897 ​ $ 404,732 ​ $ 418,431 (1) Principal amount includes current maturities and excludes any related unamortized debt discount and debt issuance costs. See Note 5 for additional disclosures on our long-term debt. (2) The estimated fair value of the 2022 Notes, the 2023 Notes and the 2026 Notes was determined using Level 1 fair value inputs under the market approach. The fair value of the Term Loan, the Nordea Q5000 Loan and the MARAD Debt was estimated using Level 2 fair value inputs under the market approach, which was determined using a third-party evaluation of the remaining average life and outstanding principal balance of the indebtedness as compared to other obligations in the marketplace with similar terms. (3) The principal amount and estimated fair value of the 2022 Notes, the 2023 Notes and the 2026 Notes are for the entire instrument inclusive of the conversion feature, which had been accounted for in shareholders’ equity through December 31, 2020. (4) The Term Loan was fully repaid in September 2021 concurrent with our entering into the ABL Facility (Note 5). (5) The Nordea Q5000 Loan was fully repaid upon maturity in January 2021 (Note 5) .

Basis Of Presentation And New_3

Basis Of Presentation And New Accounting Standards - New Accounting Standards (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term debt	$ 261,668	$ 258,912
Common stock	1,290,697	1,327,592
Retained earnings	437,065	464,524
Deferred tax liabilities	$ 91,785	110,821
Cumulative Effect, Period of Adoption | Accounting Standards Update 2020-06 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term debt		44,100
Common stock		(41,500)
Retained earnings		6,700
Deferred tax liabilities		$ (9,300)

Company Overview (Details)

Company Overview (Details)	1 Months Ended	9 Months Ended
	Jun. 30, 2021	Sep. 30, 2021itemsegment	Mar. 31, 2021
Segment Reporting Information [Line Items]
Number of reportable segments | segment		3
Well Intervention
Segment Reporting Information [Line Items]
Number of long-term chartered vessels		2
Robotics
Segment Reporting Information [Line Items]
Number of long-term chartered vessels		2
STL
Segment Reporting Information [Line Items]
Percentage of ownership interest			70.00%
Controlling interest acquired, ownership percentage	30.00%

Details Of Certain Accounts - O

Details Of Certain Accounts - Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Contract assets	$ 367	$ 2,446
Prepaids	18,301	15,904
Deferred costs	8,792	23,522
Income tax receivable		20,787
Other receivable	28,184	29,782
Other	6,798	9,651
Total other current assets	$ 62,442	$ 102,092

Details Of Certain Accounts -_2

Details Of Certain Accounts - Other Assets, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred recertification and dry dock costs, net	$ 16,401	$ 21,464
Deferred costs	543	861
Charter deposit	12,544	12,544
Intangible assets with finite lives, net	3,579	3,809
Other	2,184	1,335
Total other assets, net	$ 35,251	$ 40,013

Details Of Certain Accounts - A

Details Of Certain Accounts - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll and related benefits	$ 26,443	$ 24,768
Accrued interest	2,760	7,098
Income tax payable	581
Deferred revenue	9,425	8,140
Asset retirement obligations	29,018	30,913
Other	17,013	16,116
Total accrued liabilities	$ 85,240	$ 87,035

Details Of Certain Accounts -_3

Details Of Certain Accounts - Other Non-Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred revenue	$ 762	$ 1,869
Other	719	2,009
Total other non-current liabilities	$ 1,481	$ 3,878

Leases - Components Of Lease Co

Leases - Components Of Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Lease, Cost [Abstract]
Operating lease cost	$ 14,336	$ 16,132	$ 45,391	$ 48,561
Variable lease cost	4,298	4,204	11,417	11,256
Short-term lease cost	6,258	12,923	13,233	30,089
Sublease income	(289)	(344)	(967)	(951)
Net lease cost	$ 24,603	$ 32,915	$ 69,074	$ 88,955

Leases - Maturities Of Operatin

Leases - Maturities Of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Less than one year	$ 61,548	$ 60,649
One to two years	47,991	57,541
Two to three years	12,702	39,229
Three to four years	3,212	6,844
Four to five years	1,048	2,340
Over five years	4,443	4,054
Total lease payments	130,944	170,657
Less: imputed interest	(11,470)	(18,049)
Total operating lease liabilities	119,474	152,608
Current operating lease liabilities	55,051	51,599
Non-current operating lease liabilities	64,423	101,009
Vessels
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Less than one year	55,817	54,621
One to two years	43,045	52,106
Two to three years	8,013	34,580
Three to four years		2,470
Total lease payments	106,875	143,777
Less: imputed interest	(7,388)	(13,352)
Total operating lease liabilities	99,487	130,425
Current operating lease liabilities	50,295	46,748
Non-current operating lease liabilities	49,192	83,677
Facilities and Equipment
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Less than one year	5,731	6,028
One to two years	4,946	5,435
Two to three years	4,689	4,649
Three to four years	3,212	4,374
Four to five years	1,048	2,340
Over five years	4,443	4,054
Total lease payments	24,069	26,880
Less: imputed interest	(4,082)	(4,697)
Total operating lease liabilities	19,987	22,183
Current operating lease liabilities	4,756	4,851
Non-current operating lease liabilities	$ 15,231	$ 17,332

Leases - Weighted Average Remai

Leases - Weighted Average Remaining Lease Term And Discount Rate (Details)	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Weighted average remaining lease term (in years)	2 years 7 months 6 days	3 years 1 month 6 days
Weighted average discount rate (as a percent)	7.59%	7.53%

Leases - Other Information Rela

Leases - Other Information Related To Operating Leases (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Cash paid for operating lease liabilities	$ 46,141	$ 49,350
Right-of-use assets obtained in exchange for new operating lease obligations	$ 5,975	$ 36

Long-Term Debt - Maturities Of

Long-Term Debt - Maturities Of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Less than one year	$ 42,937
One to two years	38,333
Two to three years	8,749
Three to four years	9,186
Four to five years	209,644
Over five years	5,001
Gross debt	313,850	$ 404,732
Unamortized debt issuance costs	(9,357)
Total debt	304,493
Less: current maturities	(42,825)	(90,651)
Long-term debt	261,668	258,912
Convertible Senior Notes Maturing May 2022
Debt Instrument [Line Items]
Less than one year	35,000
Gross debt	35,000	35,000
Unamortized debt issuance costs	(112)
Total debt	34,888
Less: current maturities	(34,888)
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
One to two years	30,000
Gross debt	30,000	30,000
Unamortized debt issuance costs	(359)
Total debt	29,641
Long-term debt	29,641
Convertible Senior Notes Maturing February 2026
Debt Instrument [Line Items]
Four to five years	200,000
Gross debt	200,000	200,000
Unamortized debt issuance costs	(6,203)
Total debt	193,797
Long-term debt	193,797
MARAD Debt Maturing February 2027
Debt Instrument [Line Items]
Less than one year	7,937
One to two years	8,333
Two to three years	8,749
Three to four years	9,186
Four to five years	9,644
Over five years	5,001
Gross debt	48,850	$ 56,410
Unamortized debt issuance costs	(2,683)
Total debt	46,167
Less: current maturities	(7,937)
Long-term debt	$ 38,230

Long-Term Debt - Credit Agreeme

Long-Term Debt - Credit Agreement (Details) $ in Thousands	Jun. 30, 2023	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Principal amount		$ 313,850	$ 404,732
ABL Facility Maturing September 2026
Debt Instrument [Line Items]
Borrowing capacity		$ 80,000
Maturity date		Sep. 30, 2026
Springing maturity period		91 days
Outstanding principal amount with a springing maturity		$ 50,000
Additional commitments (up to)		70,000
Sub-limit for the issuance of letters of credit		10,000
Borrowings under ABL Facility		0
Available borrowing capacity		69,600
Letters of credit issued		2,200
ABL Facility Maturing September 2026 | Pro Forma
Debt Instrument [Line Items]
Available borrowing capacity		$ 16,000
Available borrowing capacity (as a percent)		10.00%
Availability of the borrowing base to satisfy and maintain fixed charge ratio		$ 8,000
Period prior to maturity to maintain a pro forma minimum excess availability		91 days
ABL Facility Maturing September 2026 | Minimum
Debt Instrument [Line Items]
Commitment fee percentage		0.375%
Fixed charge coverage ratio		1
ABL Facility Maturing September 2026 | Maximum
Debt Instrument [Line Items]
Commitment fee percentage		0.50%
ABL Facility Maturing September 2026 | SOFR | Minimum | Subsequent Event
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	0.114%
ABL Facility Maturing September 2026 | SOFR | Maximum | Subsequent Event
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	0.428%
ABL Facility Maturing September 2026 | United States
Debt Instrument [Line Items]
Borrowing capacity		$ 45,000
ABL Facility Maturing September 2026 | United States | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		1.50%
ABL Facility Maturing September 2026 | United States | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		2.00%
ABL Facility Maturing September 2026 | United States | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		0.50%
ABL Facility Maturing September 2026 | United States | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		1.00%
ABL Facility Maturing September 2026 | United Kingdom
Debt Instrument [Line Items]
Borrowing capacity		$ 35,000
ABL Facility Maturing September 2026 | United Kingdom | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		1.50%
ABL Facility Maturing September 2026 | United Kingdom | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		2.00%
ABL Facility Maturing September 2026 | United Kingdom | SONIA | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		1.50%
ABL Facility Maturing September 2026 | United Kingdom | SONIA | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		2.00%

Long-Term Debt - Convertible Se

Long-Term Debt - Convertible Senior Notes Due 2022 (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)$ / shares	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Interest expense	$ 6,097,000	$ 8,007,000	$ 18,152,000	$ 22,580,000
Amortization of debt issuance costs			$ 2,596,000	2,401,000
Convertible Senior Notes Maturing May 2022
Debt Instrument [Line Items]
Interest rate (as a percent)	4.25%		4.25%
Frequency of periodic payment			semi-annually
Maturity date			May 1, 2022
Initial conversion ratio			0.0719748
Aggregate number of shares | shares			2,519,118
Initial conversion price per share (USD per share) | $ / shares	$ 13.89		$ 13.89
Increase in the conversion rate			0.0305887
Redemption price as a percentage of principal amount			100.00%
Unamortized debt discount and debt issuance costs					$ 1,500,000
Unamortized debt issuance costs	$ 100,000		$ 100,000
Effective interest rate (as a percent)	4.80%		4.80%		7.30%
Interest expense	$ 400,000	1,400,000	$ 1,300,000	6,000,000
Coupon interest expense	$ 400,000	800,000	1,100,000	3,500,000
Amortization of debt issuance costs			$ 200,000
Amortization of debt discount and issuance costs		$ 600,000		$ 2,500,000
Convertible Senior Notes Maturing May 2022 | Maximum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			130.00%
Number of trading days			20
Number of consecutive trading days			30
Convertible Senior Notes Maturing May 2022 | Minimum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			97.00%
Number of trading days			5
Number of consecutive trading days			10

Long-Term Debt - Convertible _2

Long-Term Debt - Convertible Senior Notes Due 2023 (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)$ / shares	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Interest expense	$ 6,097,000	$ 8,007,000	$ 18,152,000	$ 22,580,000
Amortization of debt issuance costs			$ 2,596,000	2,401,000
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
Interest rate (as a percent)	4.125%		4.125%
Frequency of periodic payment			semi-annually
Maturity date			Sep. 15, 2023
Initial conversion ratio			0.1056133
Aggregate number of shares | shares			3,168,399
Initial conversion price per share (USD per share) | $ / shares	$ 9.47		$ 9.47
Increase in the conversion rate			0.0475260
Redemption price as a percentage of principal amount			100.00%
Unamortized debt discount and debt issuance costs					$ 3,100,000
Unamortized debt issuance costs	$ 400,000		$ 400,000
Effective interest rate (as a percent)	4.80%		4.80%		7.80%
Interest expense	$ 300,000	1,400,000	$ 1,000,000	6,000,000
Coupon interest expense	$ 300,000	800,000	900,000	3,400,000
Amortization of debt issuance costs			$ 100,000
Amortization of debt discount and issuance costs		$ 600,000		$ 2,600,000
Convertible Senior Notes Maturing September 2023 | Maximum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			130.00%
Number of trading days			20
Number of consecutive trading days			30
Convertible Senior Notes Maturing September 2023 | Minimum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			97.00%
Number of trading days			5
Number of consecutive trading days			10

Long-Term Debt - Convertible _3

Long-Term Debt - Convertible Senior Notes Due 2026 (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)$ / shares	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Interest expense	$ 6,097,000	$ 8,007,000	$ 18,152,000	$ 22,580,000
Amortization of debt issuance costs			$ 2,596,000	2,401,000
Convertible Senior Notes Maturing February 2026
Debt Instrument [Line Items]
Interest rate (as a percent)	6.75%		6.75%
Maturity date			Feb. 15, 2026
Frequency of periodic payment			semi-annually
Initial conversion ratio			0.1433795
Aggregate number of shares | shares			28,675,900
Initial conversion price per share (USD per share) | $ / shares	$ 6.97		$ 6.97
Increase in the conversion rate			0.0645207
Redemption price as a percentage of principal amount			100.00%
Unamortized debt discount and debt issuance costs					$ 47,300,000
Unamortized debt issuance costs	$ 6,200,000		$ 6,200,000
Effective interest rate (as a percent)	7.60%		7.60%		12.40%
Interest expense	$ 3,700,000	2,500,000	$ 11,000,000	2,500,000
Coupon interest expense	3,400,000	1,700,000	10,100,000	1,700,000
Amortization of debt issuance costs	$ 300,000	$ 800,000	$ 900,000	$ 800,000
Convertible Senior Notes Maturing February 2026 | Maximum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			130.00%
Number of trading days			20
Number of consecutive trading days			30
Convertible Senior Notes Maturing February 2026 | Minimum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			97.00%
Number of trading days			5
Number of consecutive trading days			10

Long-Term Debt - 2026 Capped Ca

Long-Term Debt - 2026 Capped Calls (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Aggregate cost of capped call transactions	$ 10,625		$ 10,625
2026 Capped Calls
Debt Instrument [Line Items]
Aggregate number of common shares subject to capped calls		28,675,900
Initial strike price		$ 6.97
Initial cap price		$ 8.42
Aggregate cost of capped call transactions		$ 10,600

Long-Term Debt - MARAD Debt (De

Long-Term Debt - MARAD Debt (Details) - MARAD Debt Maturing February 2027	9 Months Ended
	Sep. 30, 2021
Debt Instrument [Line Items]
Guarantor obligations (as a percent)	50.00%
Frequency of periodic payment	semi-annual
Maturity date	February 2027
Interest rate (as a percent)	4.93%

Long-Term Debt - Former Nordea

Long-Term Debt - Former Nordea Q5000 Loan (Details) $ in Millions	Jan. 31, 2021USD ($)
Nordea Q5000 Loan Matured January 2021
Debt Instrument [Line Items]
Balloon payment	$ 53.6

Long-Term Debt - Former Credit

Long-Term Debt - Former Credit Agreement (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020
Revolving Credit Facility Previously Maturing December 2021
Debt Instrument [Line Items]
Borrowing capacity	$ 175,000	$ 175,000
Borrowings under Revolving Credit Facility	0	0
Term Loan Repaid September 2021
Debt Instrument [Line Items]
Repayment of Term Loan	$ 28,000	$ 29,826	$ 2,625

Long-Term Debt - Components Of

Long-Term Debt - Components Of Net Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Disclosure [Abstract]
Interest expense	$ 6,097	$ 8,007	$ 18,152	$ 22,580
Capitalized interest				(1,182)
Interest income	(169)	(409)	(252)	(991)
Net interest expense	$ 5,928	$ 7,598	$ 17,900	$ 20,407

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020USD ($)subsidiary
Income Tax Disclosure [Abstract]
Net tax benefit from CARES Act				$ 7.6
Current tax benefit from CARES Act				18.9
Deferred tax expense from CARES Act				$ 11.3
Number of foreign subsidiaries | subsidiary				2
Net deferred tax benefit from foreign subsidiary restructuring				$ 8.3
Effective tax rate	5.30%	17.60%	7.50%	9777.00%

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Taxes at U.S. statutory rate	$ (4,221)	$ 6,232	$ (8,124)	$ (35)
Foreign tax provision	5,134	1,088	3,669	(28)
CARES Act		(2,362)		(7,596)
Subsidiary restructuring				(8,333)
Other	(1,971)	274	1,545	(140)
Income tax benefit	$ (1,058)	$ 5,232	$ (2,910)	$ (16,132)
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Taxes at U.S. statutory rate	21.00%	21.00%	21.00%	21.00%
Foreign tax provision	(25.50%)	3.70%	(9.50%)	17.00%
CARES Act		(8.00%)		4603.60%
Subsidiary restructuring				5050.30%
Other	9.80%	0.90%	(4.00%)	85.10%
Income tax benefit	5.30%	17.60%	7.50%	9777.00%
Interim period allocations	$ (1,700)	$ 2,300	$ 1,100	$ 2,300

Revenue From Contracts With C_3

Revenue From Contracts With Customers - Disaggregation Of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Net revenues	$ 180,716	$ 193,490	$ 506,072	$ 573,658
Intercompany Eliminations
Disaggregation of Revenue [Line Items]
Net revenues	(11,773)	(11,282)	(36,962)	(32,835)
Well Intervention
Disaggregation of Revenue [Line Items]
Net revenues	131,314	140,803	397,387	427,296
Well Intervention | Intercompany Eliminations
Disaggregation of Revenue [Line Items]
Net revenues	(4,267)	(4,120)	(17,060)	(11,334)
Robotics
Disaggregation of Revenue [Line Items]
Net revenues	42,623	49,802	96,430	135,896
Robotics | Intercompany Eliminations
Disaggregation of Revenue [Line Items]
Net revenues	(7,506)	(7,162)	(19,902)	(21,501)
Production Facilities
Disaggregation of Revenue [Line Items]
Net revenues	18,552	14,167	49,217	43,301
Short-term
Disaggregation of Revenue [Line Items]
Net revenues	123,140	75,689	279,445	271,906
Short-term | Well Intervention
Disaggregation of Revenue [Line Items]
Net revenues	92,954	46,907	218,840	184,599
Short-term | Robotics
Disaggregation of Revenue [Line Items]
Net revenues	30,186	28,782	60,605	87,307
Long-term
Disaggregation of Revenue [Line Items]
Net revenues	57,576	117,801	226,627	301,752
Long-term | Intercompany Eliminations
Disaggregation of Revenue [Line Items]
Net revenues	(11,773)	(11,282)	(36,962)	(32,835)
Long-term | Well Intervention
Disaggregation of Revenue [Line Items]
Net revenues	38,360	93,896	178,547	242,697
Long-term | Robotics
Disaggregation of Revenue [Line Items]
Net revenues	12,437	21,020	35,825	48,589
Long-term | Production Facilities
Disaggregation of Revenue [Line Items]
Net revenues	$ 18,552	$ 14,167	$ 49,217	$ 43,301

Revenue From Contracts With C_4

Revenue From Contracts With Customers - Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract assets	$ 0.4		$ 0.4		$ 2.4
Credit losses on contract assets	0	$ 0	0	$ 0
Contract liabilities	10.2		10.2		10
Revenue recognized	4	3.4	6.7	8.8
Deferred contract costs	9.3		9.3		$ 24.4
Amortization of deferred contract costs	$ 11.7	$ 9.2	$ 31.6	$ 27.2

Revenue From Contracts With C_5

Revenue From Contracts With Customers - Remaining Performance Obligations (Details) $ in Millions	Sep. 30, 2021USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Unsatisfied performance obligations	$ 230.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Unsatisfied performance obligations	$ 68.6
Expected timing of satisfaction	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Unsatisfied performance obligations	$ 102.6
Expected timing of satisfaction	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Unsatisfied performance obligations	$ 59.3
Expected timing of satisfaction	12 months

Earnings Per Share - Computatio

Earnings Per Share - Computations Of Basic And Diluted EPS (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic:
Net income (loss) attributable to common shareholders	$ (19,043)	$ 24,499	$ (35,630)	$ 18,011
Less: Undistributed earnings allocated to participating securities		(180)		(117)
Less: Accretion of redeemable noncontrolling interests		(128)	(241)	(2,283)
Net income (loss) available to common shareholders, basic	$ (19,043)	$ 24,191	$ (35,871)	$ 15,611
Weighted average number of shares outstanding, basic (in shares)	150,088	149,032	150,018	148,956
Diluted:
Net income (loss) available to common shareholders, basic	$ (19,043)	$ 24,191	$ (35,871)	$ 15,611
Weighted average number of shares outstanding, basic (in shares)	150,088	149,032	150,018	148,956
Effect of dilutive securities:
Share-based awards other than participating securities (in shares)		919		868
Undistributed earnings reallocated to participating securities		$ 2		$ 1
Net income (loss) available to common shareholders, diluted	$ (19,043)	$ 24,193	$ (35,871)	$ 15,612
Weighted average number of shares outstanding, diluted (in shares)	150,088	149,951	150,018	149,824

Earnings Per Share - Shares Inc

Earnings Per Share - Shares Included in Diluted Calculations Assuming Earnings (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Diluted shares (as reported)	150,088	149,951	150,018	149,824
Share-based awards	1,384		1,306
Total	151,472		151,324

Earnings Per Share - Potentiall

Earnings Per Share - Potentially Dilutive Shares Excluded From Diluted EPS Calculation (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Convertible Senior Notes Maturing May 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	2,519	5,688	2,519	7,886
Convertible Senior Notes Maturing September 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	3,168	8,076	3,168	11,481
Convertible Senior Notes Maturing February 2026
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	28,676	14,650	28,676	4,919

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Details) $ in Millions	Jan. 04, 2021item	Jan. 31, 2021USD ($)shares	Sep. 30, 2021USD ($)shares	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)shares	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
2005 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance (in shares) | shares			5,900,000		5,900,000
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards granted (in shares) | shares					0
Compensation cost | $			$ 0.8	$ 1.1	$ 2.5	$ 3.2
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of components of equity awards granted | item	2
Percentage based on service and market conditions	50.00%
Percentage based on service and performance conditions	50.00%
Compensation cost | $			1	1	3.1	3
Performance Period		3 years
Share-based payment awards vested (in shares) | shares		368,038
Award vesting percentage		200.00%
Performance Share Units | Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment awards vested (in shares) | shares		736,075
Fair value of awards vested | $		$ 3.1
Performance Share Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	200.00%
Performance Share Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	0.00%
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost | $					0.4
Fixed Value Cash Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Long-term incentive cash awards granted | $			3.5		$ 3.5		$ 4.7
Vesting period					3 years
Deferred compensation cost | $			$ 1	$ 1.1	$ 3	$ 3.4
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance (in shares) | shares			1,600,000		1,600,000
Purchase limit per employee (in shares) | shares					260

Employee Benefit Plans - Share-

Employee Benefit Plans - Share-Based Awards Granted (Details)	Jul. 23, 2021$ / sharesshares	Jul. 01, 2021$ / sharesshares	Apr. 01, 2021$ / sharesshares	Jan. 04, 2021item$ / sharesshares	Jan. 01, 2021$ / sharesshares	Jan. 31, 2021	Sep. 30, 2021shares
RSUs | Management and Employee
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Date of Grant					Jan. 1, 2021
Shares/Units					452,381
Grant Date Fair Value Per Share/Unit | $ / shares					$ 4.20
Vesting Percentage					33.00%
Vesting Period					3 years
Performance Share Units
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Vesting Percentage						200.00%
Percentage based on service and market conditions				50.00%
Percentage based on service and performance conditions				50.00%
Number of components of equity awards granted | item				2
Performance Share Units | Management and Employee
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Date of Grant				Jan. 4, 2021
Shares/Units				452,381
Grant Date Fair Value Per Share/Unit | $ / shares				$ 5.33
Vesting Percentage				100.00%
Vesting Date				Jan. 4, 2024
Restricted Stock
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares/Units							0
Restricted Stock | Board of Directors
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Date of Grant	Jul. 23, 2021	Jul. 1, 2021	Apr. 1, 2021	Jan. 4, 2021
Shares/Units	14,664	8,403	9,282	14,249
Grant Date Fair Value Per Share/Unit | $ / shares	$ 4.54	$ 5.71	$ 5.05	$ 4.20
Vesting Percentage	100.00%	100.00%	100.00%	100.00%
Vesting Date	Jul. 23, 2022	Jan. 1, 2023	Jan. 1, 2023	Jan. 1, 2023

Business Segment Information -

Business Segment Information - Narrative (Details)	9 Months Ended
	Sep. 30, 2021itemsegment
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Robotics
Segment Reporting Information [Line Items]
Number of long-term chartered vessels | item	2

Business Segment Information _2

Business Segment Information - Financial Data By Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Net revenues	$ 180,716	$ 193,490	$ 506,072	$ 573,658
Goodwill impairment				(6,689)
Income from operations	(10,331)	19,015	(21,827)	12,182
Reportable Segments
Segment Reporting Information [Line Items]
Income from operations	(3,318)	29,961	3,723	47,992
Intercompany Eliminations
Segment Reporting Information [Line Items]
Net revenues	(11,773)	(11,282)	(36,962)	(32,835)
Corporate, Eliminations and Other
Segment Reporting Information [Line Items]
Income from operations	(7,013)	(10,946)	(25,550)	(29,121)
Well Intervention
Segment Reporting Information [Line Items]
Net revenues	131,314	140,803	397,387	427,296
Well Intervention | Reportable Segments
Segment Reporting Information [Line Items]
Net revenues	131,314	140,803	397,387	427,296
Income from operations	(13,343)	18,844	(14,819)	24,910
Well Intervention | Intercompany Eliminations
Segment Reporting Information [Line Items]
Net revenues	(4,267)	(4,120)	(17,060)	(11,334)
Robotics
Segment Reporting Information [Line Items]
Net revenues	42,623	49,802	96,430	135,896
Robotics | Reportable Segments
Segment Reporting Information [Line Items]
Net revenues	42,623	49,802	96,430	135,896
Income from operations	4,936	6,983	2,257	11,940
Robotics | Intercompany Eliminations
Segment Reporting Information [Line Items]
Net revenues	(7,506)	(7,162)	(19,902)	(21,501)
Production Facilities
Segment Reporting Information [Line Items]
Net revenues	18,552	14,167	49,217	43,301
Production Facilities | Reportable Segments
Segment Reporting Information [Line Items]
Net revenues	18,552	14,167	49,217	43,301
Income from operations	$ 5,089	$ 4,134	$ 16,285	$ 11,142

Business Segment Information _3

Business Segment Information - Intercompany Segment Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Net revenues	$ (180,716)	$ (193,490)	$ (506,072)	$ (573,658)
Well Intervention
Segment Reporting Information [Line Items]
Net revenues	(131,314)	(140,803)	(397,387)	(427,296)
Robotics
Segment Reporting Information [Line Items]
Net revenues	(42,623)	(49,802)	(96,430)	(135,896)
Intercompany Eliminations
Segment Reporting Information [Line Items]
Net revenues	11,773	11,282	36,962	32,835
Intercompany Eliminations | Well Intervention
Segment Reporting Information [Line Items]
Net revenues	4,267	4,120	17,060	11,334
Intercompany Eliminations | Robotics
Segment Reporting Information [Line Items]
Net revenues	$ 7,506	$ 7,162	$ 19,902	$ 21,501

Business Segment Information _4

Business Segment Information - Total Assets By Reportable Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total assets	$ 2,347,299	$ 2,498,278
Corporate, Eliminations and Other
Segment Reporting Information [Line Items]
Total assets	74,411	101,874
Well Intervention | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	2,042,180	2,134,081
Robotics | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	109,450	132,550
Production Facilities | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	$ 121,258	$ 129,773

Asset Retirement Obligations -

Asset Retirement Obligations - Asset Retirement Obligations (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
AROs at beginning of year	$ 30,913	$ 28,258
Revisions in estimates	(2,631)
Accretion expense	736	2,021
AROs at end of period	$ 29,018	$ 30,279

Commitments And Contingencies_2

Commitments And Contingencies And Other Matters - Narrative (Details)	9 Months Ended
	Sep. 30, 2021
Siem Helix 1 and Siem Helix 2
Commitments And Contingencies [Line Items]
Term of charter agreement	7 years

Statement Of Cash Flow Inform_3

Statement Of Cash Flow Information - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Supplemental cash flow information
Interest paid, net of interest capitalized	$ 19,945	$ 14,255
Income Taxes Paid	6,771	$ 6,436
CARES Act and COVID-19 Income Tax Refunds
Supplemental cash flow information
Tax refunds related to the CARES Act	$ 18,900

Statement Of Cash Flow Inform_4

Statement Of Cash Flow Information - Narrative (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Supplemental Cash Flow Information [Abstract]
Non-cash capital additions	$ 0.3	$ 1.6

Allowance For Credit Losses - A

Allowance For Credit Losses - Activities In Allowance For Credit Losses (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	$ 3,469
Additions (reductions)	(213)	$ 2,387
Write-offs	(1,846)
Balance at end of period	$ 1,410	3,172
Cumulative Effect, Period of Adoption | Accounting Standards Update 2016-13
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year		785
Robotics
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Additions (reductions)		$ 1,700

Fair Value Measurements - Princ

Fair Value Measurements - Principal Amount And Estimated Fair Value Of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount	$ 313,850	$ 404,732
Fair value	326,897	418,431
Term Loan Repaid September 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount		29,750
Fair value		28,969
Nordea Q5000 Loan Matured January 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount		53,572
Fair value		53,598
MARAD Debt Maturing February 2027
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount	48,850	56,410
Fair value	53,115	62,318
Convertible Senior Notes Maturing May 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount	35,000	35,000
Fair value	34,638	33,513
Convertible Senior Notes Maturing September 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount	30,000	30,000
Fair value	29,001	28,650
Convertible Senior Notes Maturing February 2026
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount	200,000	200,000
Fair value	$ 210,143	$ 211,383