Helix Energy Solutions (HLX) 10-Q 28 Jul 21 2021 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Jul. 22, 2021
Document And Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 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		150,795,082
Entity Central Index Key	0000866829
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 243,911	$ 291,320
Restricted cash	71,282
Accounts receivable, net of allowance for credit losses of $1,548 and $3,469, respectively	125,569	132,233
Other current assets	78,869	102,092
Total current assets	519,631	525,645
Property and equipment	2,964,068	2,948,907
Less accumulated depreciation	(1,228,891)	(1,165,943)
Property and equipment, net	1,735,177	1,782,964
Operating lease right-of-use assets	125,481	149,656
Other assets, net	37,418	40,013
Total assets	2,417,707	2,498,278
Current liabilities:
Accounts payable	70,105	50,022
Accrued liabilities	83,618	87,035
Current maturities of long-term debt	70,492	90,651
Current operating lease liabilities	50,769	51,599
Total current liabilities	274,984	279,307
Long-term debt	265,222	258,912
Operating lease liabilities	76,934	101,009
Deferred tax liabilities	97,906	110,821
Other non-current liabilities	2,601	3,878
Total liabilities	717,647	753,927
Redeemable noncontrolling interests		3,855
Shareholders' equity:
Common stock, no par, 240,000 shares authorized, 150,787 and 150,341 shares issued, respectively	1,288,603	1,327,592
Retained earnings	456,108	464,524
Accumulated other comprehensive loss	(44,651)	(51,620)
Total shareholders' equity	1,700,060	1,740,496
Total liabilities, redeemable noncontrolling interests and shareholders' equity	$ 2,417,707	$ 2,498,278

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Allowance for credit losses	$ 1,548	$ 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	150,787	150,341

Condensed Consolidated Statemen

Condensed Consolidated Statements Of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Net revenues	$ 161,941	$ 199,147	$ 325,356	$ 380,168
Cost of sales	158,811	169,571	307,602	348,582
Gross profit	3,130	29,576	17,754	31,586
Gain (loss) on disposition of assets, net	(646)	473	(646)	473
Goodwill impairment				(6,689)
Selling, general and administrative expenses	(13,425)	(15,855)	(28,604)	(32,203)
Income (loss) from operations	(10,941)	14,194	(11,496)	(6,833)
Net interest expense	(5,919)	(7,063)	(11,972)	(12,809)
Other income (expense), net	960	(2,069)	2,577	(12,496)
Royalty income and other	249	117	2,306	2,296
Income (loss) before income taxes	(15,651)	5,179	(18,585)	(29,842)
Income tax benefit	(1,968)	(271)	(1,852)	(21,364)
Net income (loss)	(13,683)	5,450	(16,733)	(8,478)
Net income (loss) attributable to redeemable noncontrolling interests	26		(146)	(1,990)
Net income (loss) attributable to common shareholders	$ (13,709)	$ 5,450	$ (16,587)	$ (6,488)
Earnings (loss) per share of common stock:
Basic	$ (0.09)	$ 0.04	$ (0.11)	$ (0.06)
Diluted	$ (0.09)	$ 0.04	$ (0.11)	$ (0.06)
Weighted average common shares outstanding (in shares)
Basic	150,028	148,971	149,982	148,917
Diluted	150,028	149,691	149,982	148,917

Condensed Consolidated Statem_2

Condensed Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (13,683)	$ 5,450	$ (16,733)	$ (8,478)
Other comprehensive income (loss), net of tax:
Net unrealized gain (loss) on hedges arising during the period		1		(95)
Reclassifications into earnings		25		452
Income taxes on hedges		(6)		(72)
Net change in hedges, net of tax		20		285
Foreign currency translation gain (loss)	2,356	(1,896)	6,969	(35,483)
Other comprehensive income (loss), net of tax	2,356	(1,876)	6,969	(35,198)
Comprehensive income (loss)	(11,327)	3,574	(9,764)	(43,676)
Less comprehensive income (loss) attributable to redeemable noncontrolling interests:
Net income (loss)	26		(146)	(1,990)
Foreign currency translation gain (loss)	12	(20)	48	(248)
Comprehensive income (loss) attributable to redeemable noncontrolling interests	38	(20)	(98)	(2,238)
Comprehensive income (loss) attributable to common shareholders	$ (11,365)	$ 3,594	$ (9,666)	$ (41,438)

Condensed Consolidated Statem_3

Condensed Consolidated Statements Of Shareholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common StockCumulative-effect adjustments upon adoption of ASU	Common Stock	Retained EarningsCumulative-effect adjustments upon adoption of ASU	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Cumulative-effect adjustments upon adoption of ASU	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)				(6,488)			(6,488)
Foreign currency translation adjustments					(35,483)		(35,483)
Unrealized gain on hedges, net of tax					285		285
Accretion of redeemable noncontrolling interests				(2,155)			(2,155)
Activity in company stock plans, net and other		$ (4,513)					(4,513)
Activity in company stock plans, net and other (in shares)		1,152
Share-based compensation		$ 4,083					4,083
Balance, end of period at Jun. 30, 2020		$ 1,318,531		436,107	(99,938)		1,654,700
Balance, end of period (in shares) at Jun. 30, 2020		150,040
Balance, beginning of period at Dec. 31, 2019							3,455
Increase (Decrease) in Redeemable Noncontrolling Interests [Roll Forward]
Net income (loss)							(1,990)
Foreign currency translation adjustments related to redeemable noncontrolling interests							(248)
Accretion of redeemable noncontrolling interests							2,155
Balance, end of period at Jun. 30, 2020							3,372
Balance, beginning of period at Mar. 31, 2020		$ 1,316,401		430,726	(98,062)		1,649,065
Balance, beginning of period (in shares) at Mar. 31, 2020		149,962
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)				5,450			5,450
Foreign currency translation adjustments					(1,896)		(1,896)
Unrealized gain on hedges, net of tax					20		20
Accretion of redeemable noncontrolling interests				(69)			(69)
Activity in company stock plans, net and other		$ 217					217
Activity in company stock plans, net and other (in shares)		78
Share-based compensation		$ 1,913					1,913
Balance, end of period at Jun. 30, 2020		$ 1,318,531		436,107	(99,938)		1,654,700
Balance, end of period (in shares) at Jun. 30, 2020		150,040
Balance, beginning of period at Mar. 31, 2020							3,323
Increase (Decrease) in Redeemable Noncontrolling Interests [Roll Forward]
Foreign currency translation adjustments related to redeemable noncontrolling interests							(20)
Accretion of redeemable noncontrolling interests							69
Balance, end of period at Jun. 30, 2020							3,372
Balance, beginning of period (Accounting Standards Update 2020-06) 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)				(16,587)			(16,587)
Foreign currency translation adjustments					6,969		6,969
Accretion of redeemable noncontrolling interests							(241)
Accretion of redeemable noncontrolling interests				1,489			1,489
Activity in company stock plans, net and other		$ (1,314)					(1,314)
Activity in company stock plans, net and other (in shares)		446
Share-based compensation		$ 3,781					3,781
Balance, end of period at Jun. 30, 2021		$ 1,288,603		456,108	(44,651)		1,700,060
Balance, end of period (in shares) at Jun. 30, 2021		150,787
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 Mar. 31, 2021		$ 1,286,380		468,087	(47,007)		1,707,460
Balance, beginning of period (in shares) at Mar. 31, 2021		150,715
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)				(13,709)			(13,709)
Foreign currency translation adjustments					2,356		2,356
Accretion of redeemable noncontrolling interests				1,730			1,730
Activity in company stock plans, net and other		$ 286					286
Activity in company stock plans, net and other (in shares)		72
Share-based compensation		$ 1,937					1,937
Balance, end of period at Jun. 30, 2021		$ 1,288,603		$ 456,108	$ (44,651)		1,700,060
Balance, end of period (in shares) at Jun. 30, 2021		150,787
Balance, beginning of period at Mar. 31, 2021							3,960
Increase (Decrease) in Redeemable Noncontrolling Interests [Roll Forward]
Net income (loss)							26
Foreign currency translation adjustments related to redeemable noncontrolling interests							12
Accretion of redeemable noncontrolling interests							(1,730)
Acquisition of redeemable noncontrolling interests							$ (2,268)

Condensed Consolidated Statem_4

Condensed Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Net loss	$ (16,733)	$ (8,478)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	69,507	65,567
Goodwill impairment		6,689
Amortization of debt discounts		3,316
Amortization of debt issuance costs	1,587	1,619
Share-based compensation	3,901	4,245
Deferred income taxes	(3,649)	(7,098)
(Gain) loss on disposition of assets, net	646	(473)
Unrealized gain on derivative contracts, net		(601)
Unrealized foreign currency (gain) loss	(1,366)	10,433
Changes in operating assets and liabilities:
Accounts receivable, net	6,620	(44,698)
Income tax receivable	(5,136)	19,078
Other current assets	16,017	(23,751)
Accounts payable and accrued liabilities	18,828	35,241
Other, net	7,954	16,891
Net cash provided by operating activities	92,540	6,042
Cash flows from investing activities:
Capital expenditures	(6,772)	(17,579)
Proceeds from sale of assets	11	498
Net cash used in investing activities	(6,761)	(17,081)
Cash flows from financing activities:
Repayment of Term Loan	(1,750)	(1,750)
Debt issuance costs	(43)	(310)
Acquisition of redeemable noncontrolling interests	(2,268)
Payments related to tax withholding for share-based compensation	(1,878)	(5,150)
Proceeds from issuance of ESPP shares	443	475
Net cash used in financing activities	(62,802)	(28,149)
Effect of exchange rate changes on cash and cash equivalents and restricted cash	896	(2,879)
Net increase (decrease) in cash and cash equivalents and restricted cash	23,873	(42,067)
Cash and cash equivalents and restricted cash:
Balance, beginning of year	291,320	262,561
Balance, end of period	315,193	220,494
Nordea Q5000 Loan Maturing January 2021
Cash flows from financing activities:
Repayment of Loan Debt	(53,572)	(17,858)
MARAD Debt Maturing February 2027
Cash flows from financing activities:
Repayment of Loan Debt	$ (3,734)	$ (3,556)

Basis Of Presentation And New A

Basis Of Presentation And New Accounting Standards	6 Months Ended
	Jun. 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 six-month periods ended June 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 FASB 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 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	6 Months Ended
	Jun. 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 well 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”). Prior to June 2021 we held a Our Robotics segment provides offshore construction, cable 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	6 Months Ended
	Jun. 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 2020 Contract assets (Note 7) ​ $ 626 $ 2,446 Prepaids ​ 12,536 ​ 15,904 Deferred costs (Note 7) ​ 14,084 ​ 23,522 Income tax receivable ​ 15,436 ​ 20,787 Other receivable (Note 11) ​ 27,518 ​ 29,782 Other ​ 8,669 ​ 9,651 Total other current assets ​ $ 78,869 $ 102,092 ​ Other assets, net consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 2020 Deferred recertification and dry dock costs, net ​ $ 19,405 $ 21,464 Deferred costs (Note 7) ​ 720 ​ 861 Charter deposit (1) ​ 12,544 ​ 12,544 Intangible assets with finite lives, net ​ 3,679 ​ 3,809 Other ​ 1,070 ​ 1,335 Total other assets, net ​ $ 37,418 $ 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 2020 Accrued payroll and related benefits ​ $ 26,907 $ 24,768 Accrued interest ​ ​ 6,974 ​ ​ 7,098 Deferred revenue (Note 7) ​ 9,267 ​ 8,140 Asset retirement obligations (Note 11) ​ 28,330 ​ 30,913 Other ​ 12,140 ​ 16,116 Total accrued liabilities ​ $ 83,618 $ 87,035 ​ Other non-current liabilities consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 2020 Deferred revenue (Note 7) ​ $ 1,048 $ 1,869 Other ​ 1,553 ​ 2,009 Total other non-current liabilities ​ $ 2,601 $ 3,878 ​

Leases

Leases	6 Months Ended
	Jun. 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 ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2021 2020 2021 2020 Operating lease cost ​ $ 14,839 ​ $ 16,106 ​ $ 31,055 $ 32,429 Variable lease cost ​ 3,635 ​ 3,840 ​ 7,119 ​ 7,052 Short-term lease cost ​ 5,243 ​ 9,992 ​ 6,975 ​ 17,166 Sublease income ​ (329) ​ (328) ​ (678) ​ (607) Net lease cost ​ $ 23,388 ​ $ 29,610 ​ $ 44,471 $ 56,040 ​ Maturities of our operating lease liabilities as of June 30, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Facilities and ​ ​ ​ Vessels Equipment Total Less than one year ​ $ 52,106 ​ $ 5,884 $ 57,990 One to two years ​ 49,760 ​ 5,185 ​ 54,945 Two to three years ​ 13,557 ​ 4,722 ​ 18,279 Three to four years ​ — ​ 4,145 ​ 4,145 Four to five years ​ — ​ 1,041 ​ 1,041 Over five years ​ — ​ 4,835 ​ 4,835 Total lease payments ​ $ 115,423 ​ $ 25,812 $ 141,235 Less: imputed interest ​ (9,021) ​ (4,511) ​ (13,532) Total operating lease liabilities ​ $ 106,402 ​ $ 21,301 $ 127,703 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current operating lease liabilities ​ $ 45,940 ​ $ 4,829 $ 50,769 Non-current operating lease liabilities ​ 60,462 ​ 16,472 ​ 76,934 Total operating lease liabilities ​ $ 106,402 ​ $ 21,301 $ 127,703 ​ 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: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 ​ 2020 Weighted average remaining lease term 2.8 years ​ 3.1 years Weighted average discount rate 7.51 % ​ 7.53 % ​ The following table presents other information related to our operating leases (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ 2021 2020 Cash paid for operating lease liabilities ​ $ 31,562 $ 32,731 ROU assets obtained in exchange for new operating lease obligations ​ 1,500 ​ — ​

Long-Term Debt

Long-Term Debt	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Long-term Debt	Note 5 — Long-Term Debt Scheduled maturities of our long-term debt outstanding as of June 30, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Term ​ 2022 ​ 2023 ​ 2026 ​ MARAD ​ ​ ​ Loan Notes Notes Notes Debt Total Less than one year ​ $ 28,000 ​ $ 35,000 ​ $ — ​ $ — ​ $ 7,746 $ 70,746 One to two years ​ — ​ — ​ — ​ — ​ 8,133 ​ 8,133 Two to three years ​ — ​ — ​ 30,000 ​ — ​ 8,538 ​ 38,538 Three to four years ​ — ​ — ​ — ​ — ​ 8,965 ​ 8,965 Four to five years ​ — ​ — ​ — ​ 200,000 ​ 9,412 ​ 209,412 Over five years ​ — ​ — ​ — ​ — ​ 9,882 ​ 9,882 Gross debt ​ 28,000 ​ 35,000 ​ 30,000 ​ 200,000 ​ 52,676 ​ 345,676 Unamortized debt issuance costs (1) ​ (95) ​ (159) ​ (402) ​ (6,501) ​ (2,805) ​ (9,962) Total debt ​ 27,905 ​ 34,841 ​ 29,598 ​ 193,499 ​ 49,871 ​ 335,714 Less current maturities ​ (27,905) ​ (34,841) ​ — ​ — ​ (7,746) ​ (70,492) Long-term debt ​ $ — ​ $ — ​ $ 29,598 ​ $ 193,499 ​ $ 42,125 $ 265,222 (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 We have a credit agreement (and the amendments made thereafter, collectively the “Credit Agreement”) with a group of lenders led by Bank of America, N.A. (“Bank of America”). The Credit Agreement is comprised of a Term Loan with a remaining balance of $28.0 million as of June 30, 2021 and a Revolving Credit Facility with a maximum availability of $175 million. The Credit Agreement expires and the Term Loan matures on December 31, 2021 . The Revolving Credit Facility permits us to obtain letters of credit up to a sublimit of $25 million. Pursuant to the Credit Agreement, subject to existing lender participation and/or the participation of new lenders, and subject to standard conditions precedent, we may request aggregate commitments of up to $100 million with respect to an increase in the Revolving Credit Facility. As of June 30, 2021, we had no borrowings under the Revolving Credit Facility, and our available borrowing capacity under that facility, based on the leverage ratios, totaled $172.3 million, net of $2.7 million of letters of credit issued under that facility. Borrowings under the Credit Agreement bear interest, at our election, at either Bank of America’s base rate, the LIBOR or a comparable successor rate, or a combination thereof. The Term Loan bearing interest at the base rate will bear interest at a per annum rate equal to Bank of America’s base rate plus a margin of 2.25%. The Term Loan bearing interest at a LIBOR rate will bear interest per annum at the LIBOR or a comparable successor rate selected by us plus a margin of 3.25%. The interest rate on the Term Loan was 3.35% as of June 30, 2021. Borrowings under the Revolving Credit Facility bearing interest at the base rate will bear interest at a per annum rate equal to Bank of America’s base rate plus a margin ranging from 1.50% to 2.50%. Borrowings under the Revolving Credit Facility bearing interest at a LIBOR rate will bear interest per annum at the LIBOR or a comparable successor rate selected by us plus a margin ranging from 2.50% to 3.50%. A letter of credit fee is payable by us equal to the applicable margin for LIBOR rate loans multiplied by the daily amount available to be drawn under the applicable letter of credit. Margins on borrowings under the Revolving Credit Facility will vary in relation to the Consolidated Total Leverage Ratio (as defined below) as provided for in the Credit Agreement. We also pay a fixed commitment fee of 0.50% per annum on the unused portion of the Revolving Credit Facility. The Term Loan principal is required to be repaid in quarterly installments of 2.5% of its aggregate principal amount, with a balloon payment at maturity. Installments are subject to adjustment for any prepayments. We may prepay indebtedness outstanding under the Term Loan without premium or penalty, but may not reborrow any amounts prepaid. We may prepay indebtedness outstanding under the Revolving Credit Facility without premium or penalty, and may reborrow any amounts prepaid up to the amount available under the Revolving Credit Facility. Our obligations under the Credit Agreement, and those of our subsidiary guarantors under their guarantee, are secured by (i) most of the assets of the parent company, (ii) the shares of our domestic subsidiaries (other than Cal Dive I – Title XI, Inc.) and of Helix Robotics Solutions Limited and (iii) most of the assets of our domestic subsidiaries (other than Cal Dive I – Title XI, Inc.) and of Helix Robotics Solutions Limited. In addition, these obligations are secured by pledges of up to 66% of the shares of certain foreign subsidiaries (restricted subsidiaries). The Credit Agreement and the other documents entered into in connection with the Credit Agreement include terms and conditions, including covenants, that we consider customary for this type of transaction. The covenants include certain restrictions on our and certain of our subsidiaries’ ability to grant liens, incur indebtedness, make investments, merge or consolidate, sell or transfer assets, pay dividends and make capital expenditures. In addition, the Credit Agreement obligates us to meet minimum ratio requirements of EBITDA to interest charges (Consolidated Interest Coverage Ratio), funded debt to EBITDA (Consolidated Total Leverage Ratio) and secured funded debt to EBITDA (Consolidated Secured Leverage Ratio). We may designate one or more of our new foreign subsidiaries as subsidiaries not generally subject to the covenants in the Credit Agreement (the “Unrestricted Subsidiaries”). The Unrestricted Subsidiaries are not pledged as collateral under the Credit Agreement, and the debt and EBITDA of the Unrestricted Subsidiaries, with the exception of Helix Q5000 Holdings, S.à r.l., a wholly owned Luxembourg subsidiary of Helix Vessel Finance S.à r.l., are not included in the calculations of our financial covenants except to the extent of any cash actually distributed by such subsidiary to Helix. 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 June 30, 2021, unamortized debt issuance costs related to the 2022 Notes were $0.2 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 six-month periods ended June 30, 2021, total interest expense related to the 2022 Notes was $0.4 million and $0.8 million, respectively, with coupon interest expense of $0.4 million and $0.7 million, respectively, and the amortization of issuance costs of $0.1 million for the six-month period ended June 30, 2021. For the three- and six-month periods ended June 30, 2020, total interest expense related to the 2022 Notes was $2.3 million and $4.5 million, respectively, with coupon interest expense of $1.3 million and $2.6 million, respectively, and the amortization of debt discount and issuance costs of $1.0 million and $1.9 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 June 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 six-month periods ended June 30, 2021, total interest expense related to the 2023 Notes was $0.3 million and $0.7 million, respectively, with coupon interest expense of $0.3 million and $0.6 million, respectively, and the amortization of issuance costs of $0.1 million for the six-month period ended June 30, 2021. For the three- and six-month periods ended June 30, 2020, total interest expense related to the 2023 Notes was $2.3 million and $4.6 million, respectively, with coupon interest expense of $1.3 million and $2.6 million, respectively, and the amortization of debt discount and issuance costs of $1.0 million and $2.0 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 June 30, 2021, unamortized debt issuance costs related to the 2026 Notes were $6.5 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 six-month periods ended June 30, 2021, total interest expense related to the 2026 Notes was $3.7 million and $7.3 million, respectively, with coupon interest expense of $3.4 million and $6.7 million, respectively, and the amortization of debt issuance costs of $0.3 million and $0.6 million, respectively. 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 This U.S. government-guaranteed financing (the “MARAD Debt”), pursuant to Title XI of the Merchant Marine Act of 1936 administered by the Maritime Administration, was used to finance the construction of the Q4000 Q4000 Other We previously had a credit agreement (the “Nordea Credit Agreement”) with a syndicated bank lending group for a term loan (the “Nordea Q5000 Loan”) to finance the construction of the Q5000 Q5000 In accordance with the Credit Agreement, the 2022 Notes, the 2023 Notes, the 2026 Notes and the MARAD Debt, we are required to comply with certain covenants, including with respect to the Credit Agreement, certain financial ratios such as a consolidated interest coverage ratio, a consolidated total leverage ratio and a consolidated secured leverage ratio, as well as the maintenance of minimum cash balance, net worth, working capital and debt-to-equity requirements. As of June 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 ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2021 2020 2021 2020 ​ Interest expense ​ $ 5,943 ​ $ 7,179 ​ $ 12,055 $ 14,573 ​ Capitalized interest ​ — ​ — ​ — ​ (1,182) ​ Interest income ​ (24) ​ (116) ​ (83) ​ (582) ​ Net interest expense ​ $ 5,919 ​ $ 7,063 ​ $ 11,972 $ 12,809 ​ ​

Income Taxes

Income Taxes	6 Months Ended
	Jun. 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. For the three- and six-month periods ended June 30, 2021, we applied the annual effective tax rate method in determining our overall income tax provision or benefit. Under this method, the estimated annual worldwide effective tax rate, adjusted for discrete tax items, is applied to the pre-tax income or loss for each interim reporting period. During the three- and six-month periods ended June 30, 2020, we utilized the discrete method to calculate income tax provision or benefit on a stand-alone basis for the interim reporting period based on management’s judgment that the discrete method was more appropriate than the annual effective tax rate method given the high degree of uncertainty in forecasting the impact of the COVID-19 pandemic on future market conditions and the overall oil and gas sector. 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 six-month period ended June 30, 2020 we recognized an estimated $5.2 million net tax benefit ($15.8 million current tax benefit and $10.6 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 six-month period ended June 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 June 30, 2021 and 2020 were 12.6% and (5.2)%, 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 six-month periods ended June 30, 2021 and 2020 were 10.0% and 71.6%, 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 and the foreign subsidiary restructuring in 2020. The primary differences between the income tax provision (benefit) at the U.S. statutory rate and our actual income tax benefit are as follows (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ Six Months Ended ​ ​ ​ June 30, ​ ​ June 30, ​ ​ 2021 2020 ​ 2021 2020 ​ Taxes at U.S. statutory rate ​ $ (3,287) 21.0 % $ 1,087 21.0 % ​ $ (3,903) 21.0 % $ (6,267) 21.0 % ​ Foreign tax provision ​ (527) 3.4 ​ (2,166) (41.8) ​ ​ (1,465) 7.9 ​ (1,116) 3.7 ​ ​ CARES Act ​ — — ​ 580 11.2 ​ ​ — — ​ (5,234) 17.6 ​ ​ Subsidiary restructuring ​ — — ​ — — ​ ​ — — ​ (8,333) 27.9 ​ ​ Other (1) ​ 1,846 (11.8) ​ 228 4.4 ​ ​ 3,516 (18.9) ​ (414) 1.4 ​ ​ Income tax benefit (2) ​ $ (1,968) 12.6 % $ (271) (5.2) % ​ $ (1,852) 10.0 % $ (21,364) 71.6 % ​ (1) Includes interim period allocations of $1.6 million and $2.8 million, respectively, for the three- and six-month periods ended June 30, 2021. (2) The negative effective tax rate for the three-month period ended June 30, 2020 was driven by tax benefits of foreign losses in relation to nominal pre-tax income.

Revenue From Contracts With Cus

Revenue From Contracts With Customers	6 Months Ended
	Jun. 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 June 30, 2021 ​ ​ ​ ​ ​ Short-term ​ $ 76,669 ​ $ 21,012 ​ $ — ​ $ — ​ $ 97,681 Long-term ​ 55,636 ​ 10,639 ​ 14,218 ​ (16,233) ​ 64,260 Total ​ $ 132,305 ​ $ 31,651 ​ $ 14,218 ​ $ (16,233) ​ $ 161,941 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended June 30, 2020 ​ ​ ​ ​ ​ Short-term ​ $ 55,368 ​ $ 36,084 ​ $ — ​ $ — ​ $ 91,452 Long-term ​ 90,473 ​ 14,752 ​ 13,593 ​ (11,123) ​ 107,695 Total ​ $ 145,841 ​ $ 50,836 ​ $ 13,593 ​ $ (11,123) ​ $ 199,147 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six months ended June 30, 2021 ​ ​ ​ ​ ​ Short-term ​ $ 125,886 ​ $ 30,419 ​ $ — ​ $ — ​ $ 156,305 Long-term ​ 140,187 ​ 23,388 ​ 30,665 ​ (25,189) ​ 169,051 Total ​ $ 266,073 ​ $ 53,807 ​ $ 30,665 ​ $ (25,189) ​ $ 325,356 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six months ended June 30, 2020 ​ ​ ​ ​ ​ Short-term ​ $ 137,692 ​ $ 58,525 ​ $ — ​ $ — ​ $ 196,217 Long-term ​ 148,801 ​ 27,569 ​ 29,134 ​ (21,553) ​ 183,951 Total ​ $ 286,493 ​ $ 86,094 ​ $ 29,134 ​ $ (21,553) ​ $ 380,168 (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. Accounts receivable that have been billed to customers are recorded as trade accounts receivable while accounts receivable that have not been billed to customers are recorded as unbilled accounts receivable. 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 $0.6 million at June 30, 2021 and $2.4 million at December 31, 2020. We had no credit losses on our contract assets for the three- and six-month periods ended June 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 $10.3 million at June 30, 2021 and $10.0 million at December 31, 2020. Revenue recognized for the three- and six-month periods ended June 30, 2021 included $4.2 million and $5.4 million, respectively, that were included in the contract liability balance at the beginning of each period. Revenue recognized for the three- and six-month periods ended June 30, 2020 included $3.5 million and $6.4 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 June 30, 2021, $291.4 million related to unsatisfied performance obligations was expected to be recognized as revenue in the future, with $152.8 million in 2021 , $92.0 million in 2022 and $46.6 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 June 30, 2021. For the three- and six-month periods ended June 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 $14.8 million at June 30, 2021 and $24.4 million at December 31, 2020. For the three- and six-month periods ended June 30, 2021, we recorded $9.5 million and $19.9 million, respectively, related to amortization of these deferred contract costs. For the three- and six-month periods ended June 30, 2020, we recorded $8.8 million and $18.0 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	6 Months Ended
	Jun. 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 ​ ​ June 30, 2021 ​ June 30, 2020 ​ Income Shares Income Shares Basic: ​ ​ Net income (loss) attributable to common shareholders ​ $ (13,709) ​ ​ $ 5,450 Less: Undistributed earnings allocated to participating securities ​ — ​ ​ ​ (37) Accretion of redeemable noncontrolling interests ​ — ​ ​ ​ (69) Net income (loss) available to common shareholders, basic ​ $ (13,709) ​ 150,028 ​ $ 5,344 148,971 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted: ​ ​ ​ Net income (loss) available to common shareholders, basic ​ $ (13,709) ​ 150,028 ​ $ 5,344 148,971 Effect of dilutive securities: ​ ​ ​ Share-based awards other than participating securities ​ — ​ — ​ — 720 Net income (loss) available to common shareholders, diluted ​ $ (13,709) ​ 150,028 ​ $ 5,344 149,691 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ Six Months Ended ​ ​ June 30, 2021 ​ June 30, 2020 ​ Income ​ Income Shares Basic: ​ ​ Net loss attributable to common shareholders ​ $ (16,587) ​ ​ $ (6,488) Less: Accretion of redeemable noncontrolling interests ​ (241) ​ ​ ​ (2,155) Net loss available to common shareholders, basic ​ $ (16,828) ​ 149,982 ​ $ (8,643) 148,917 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted: ​ ​ ​ Net loss available to common shareholders, basic ​ $ (16,828) ​ 149,982 ​ $ (8,643) 148,917 Effect of dilutive securities: ​ ​ ​ Share-based awards other than participating securities ​ — ​ — ​ — — Net loss available to common shareholders, diluted ​ $ (16,828) ​ 149,982 ​ $ (8,643) 148,917 ​ We had net losses for the three- and six-month periods ended June 30, 2021 and the six-month period ended June 30, 2020. 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 ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2021 2020 2021 2020 ​ Diluted shares (as reported) 150,028 149,691 149,982 148,917 ​ Share-based awards 1,325 — 1,282 980 ​ Total 151,353 149,691 151,264 149,897 ​ ​ 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 ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2021 2020 2021 2020 ​ 2022 Notes 2,519 8,997 2,519 8,997 ​ 2023 Notes 3,168 13,202 3,168 13,202 ​ 2026 Notes 28,676 — 28,676 — ​ ​

Employee Benefit Plans

Employee Benefit Plans	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Employee Benefit Plans	Note 9 — Employee Benefit Plans Long-Term Incentive Plan As of June 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 six-month period ended June 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 (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. 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 six-month periods ended June 30, 2021, $0.9 million and $1.7 million, respectively, were recognized as share-based compensation related to restricted stock. For the three- and six-month periods ended June 30, 2020, $1.0 million and $2.1 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 six-month periods ended June 30, 2021, $1.0 million and $2.1 million, respectively, were recognized as share-based compensation related to equity PSUs. For the three- and six-month periods ended June 30, 2020, $0.9 million and $2.0 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. For the three- and six-month periods ended June 30, 2021, $0.2 million and $0.4 million, respectively, were 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 six-month periods ended June 30, 2021, $1.0 million and $2.0 million, respectively, were recognized as compensation cost. For the three- and six-month periods ended June 30, 2020, $1.1 million and $2.3 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 June 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	6 Months Ended
	Jun. 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 well 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 ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2021 2020 ​ 2021 2020 ​ Net revenues — ​ ​ ​ ​ ​ ​ Well Intervention $ 132,305 ​ $ 145,841 ​ $ 266,073 ​ $ 286,493 ​ Robotics 31,651 ​ 50,836 ​ 53,807 ​ 86,094 ​ Production Facilities 14,218 ​ 13,593 ​ 30,665 ​ 29,134 ​ Intercompany eliminations (16,233) ​ (11,123) ​ (25,189) ​ (21,553) ​ Total $ 161,941 ​ $ 199,147 ​ $ 325,356 ​ $ 380,168 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income (loss) from operations — ​ ​ ​ ​ Well Intervention $ (6,719) ​ $ 11,758 ​ $ (1,476) ​ $ 6,066 ​ Robotics 255 ​ 7,781 ​ (2,679) ​ 4,957 ​ Production Facilities 4,682 ​ 3,365 ​ 11,196 ​ 7,008 ​ Segment operating income (loss) (1,782) ​ 22,904 ​ 7,041 ​ 18,031 ​ Goodwill impairment (1) — ​ — ​ — ​ (6,689) ​ Corporate, eliminations and other (9,159) ​ (8,710) ​ (18,537) ​ (18,175) ​ Total $ (10,941) ​ $ 14,194 ​ $ (11,496) ​ $ (6,833) ​ (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 ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2021 2020 2021 2020 ​ Well Intervention ​ $ 10,206 ​ $ 3,910 ​ $ 12,793 ​ $ 7,214 ​ Robotics ​ 6,027 ​ 7,213 ​ 12,396 ​ 14,339 ​ Total ​ $ 16,233 ​ $ 11,123 ​ $ 25,189 ​ $ 21,553 ​ ​ 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 2020 Well Intervention ​ $ 2,084,665 ​ $ 2,134,081 Robotics ​ 101,121 ​ 132,550 Production Facilities ​ 125,863 ​ 129,773 Corporate and other ​ 106,058 ​ 101,874 Total ​ $ 2,417,707 ​ $ 2,498,278 ​

Asset Retirement Obligations

Asset Retirement Obligations	6 Months Ended
	Jun. 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 ​ 48 ​ 1,304 AROs at June 30, ​ $ 28,330 ​ $ 29,562 ​

Commitments And Contingencies A

Commitments And Contingencies And Other Matters	6 Months Ended
	Jun. 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.

Statement Of Cash Flow Informat

Statement Of Cash Flow Information	6 Months Ended
	Jun. 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ 2021 2020 Interest paid, net of interest capitalized ​ $ 10,601 ​ $ 8,413 Income taxes paid ​ 4,588 ​ 4,937 ​ Our capital additions include the acquisition of property and equipment for which payment has not been made. These non-cash capital additions totaled $0.4 million at June 30, 2021 and $1.6 million at December 31, 2020.

Allowance For Credit Losses

Allowance For Credit Losses	6 Months Ended
	Jun. 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) ​ (76) ​ 2,424 Write-offs (2) ​ ​ (1,845) ​ ​ — Adjustments (3) ​ — ​ 785 Balance at June 30, ​ $ 1,548 ​ $ 3,209 (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	6 Months Ended
	Jun. 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ December 31, 2020 ​ ​ Principal ​ Fair ​ Principal ​ Fair ​ Amount (1) Value (2) (3) Amount (1) Value (2) (3) Term Loan (matures December 2021) ​ $ 28,000 ​ $ 27,895 ​ $ 29,750 ​ $ 28,969 Nordea Q5000 Loan (matured January 2021) (4) ​ — ​ — ​ 53,572 ​ 53,598 MARAD Debt (matures February 2027) ​ 52,676 ​ 56,542 ​ 56,410 ​ 62,318 2022 Notes (mature May 2022) ​ 35,000 ​ 35,199 ​ 35,000 ​ 33,513 2023 Notes (mature September 2023) ​ 30,000 ​ 29,662 ​ 30,000 ​ 28,650 2026 Notes (mature February 2026) ​ 200,000 ​ 247,359 ​ 200,000 ​ 211,383 Total debt ​ $ 345,676 ​ $ 396,657 ​ $ 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 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)	6 Months Ended
	Jun. 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 six-month periods ended June 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 FASB 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 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)	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of other current assets	Other current assets consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 2020 Contract assets (Note 7) ​ $ 626 $ 2,446 Prepaids ​ 12,536 ​ 15,904 Deferred costs (Note 7) ​ 14,084 ​ 23,522 Income tax receivable ​ 15,436 ​ 20,787 Other receivable (Note 11) ​ 27,518 ​ 29,782 Other ​ 8,669 ​ 9,651 Total other current assets ​ $ 78,869 $ 102,092
Schedule of other assets, net	Other assets, net consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 2020 Deferred recertification and dry dock costs, net ​ $ 19,405 $ 21,464 Deferred costs (Note 7) ​ 720 ​ 861 Charter deposit (1) ​ 12,544 ​ 12,544 Intangible assets with finite lives, net ​ 3,679 ​ 3,809 Other ​ 1,070 ​ 1,335 Total other assets, net ​ $ 37,418 $ 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 2020 Accrued payroll and related benefits ​ $ 26,907 $ 24,768 Accrued interest ​ ​ 6,974 ​ ​ 7,098 Deferred revenue (Note 7) ​ 9,267 ​ 8,140 Asset retirement obligations (Note 11) ​ 28,330 ​ 30,913 Other ​ 12,140 ​ 16,116 Total accrued liabilities ​ $ 83,618 $ 87,035
Schedule of other non-current liabilities	Other non-current liabilities consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 2020 Deferred revenue (Note 7) ​ $ 1,048 $ 1,869 Other ​ 1,553 ​ 2,009 Total other non-current liabilities ​ $ 2,601 $ 3,878

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 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 ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2021 2020 2021 2020 Operating lease cost ​ $ 14,839 ​ $ 16,106 ​ $ 31,055 $ 32,429 Variable lease cost ​ 3,635 ​ 3,840 ​ 7,119 ​ 7,052 Short-term lease cost ​ 5,243 ​ 9,992 ​ 6,975 ​ 17,166 Sublease income ​ (329) ​ (328) ​ (678) ​ (607) Net lease cost ​ $ 23,388 ​ $ 29,610 ​ $ 44,471 $ 56,040
Schedule of maturities of operating lease liabilities	Maturities of our operating lease liabilities as of June 30, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Facilities and ​ ​ ​ Vessels Equipment Total Less than one year ​ $ 52,106 ​ $ 5,884 $ 57,990 One to two years ​ 49,760 ​ 5,185 ​ 54,945 Two to three years ​ 13,557 ​ 4,722 ​ 18,279 Three to four years ​ — ​ 4,145 ​ 4,145 Four to five years ​ — ​ 1,041 ​ 1,041 Over five years ​ — ​ 4,835 ​ 4,835 Total lease payments ​ $ 115,423 ​ $ 25,812 $ 141,235 Less: imputed interest ​ (9,021) ​ (4,511) ​ (13,532) Total operating lease liabilities ​ $ 106,402 ​ $ 21,301 $ 127,703 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current operating lease liabilities ​ $ 45,940 ​ $ 4,829 $ 50,769 Non-current operating lease liabilities ​ 60,462 ​ 16,472 ​ 76,934 Total operating lease liabilities ​ $ 106,402 ​ $ 21,301 $ 127,703 ​ 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: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 ​ 2020 Weighted average remaining lease term 2.8 years ​ 3.1 years Weighted average discount rate 7.51 % ​ 7.53 %
Schedule of other information related to operating leases	The following table presents other information related to our operating leases (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ 2021 2020 Cash paid for operating lease liabilities ​ $ 31,562 $ 32,731 ROU assets obtained in exchange for new operating lease obligations ​ 1,500 ​ —

Long-Term Debt (Tables)

Long-Term Debt (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Schedule of maturities of long-term debt outstanding	Scheduled maturities of our long-term debt outstanding as of June 30, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Term ​ 2022 ​ 2023 ​ 2026 ​ MARAD ​ ​ ​ Loan Notes Notes Notes Debt Total Less than one year ​ $ 28,000 ​ $ 35,000 ​ $ — ​ $ — ​ $ 7,746 $ 70,746 One to two years ​ — ​ — ​ — ​ — ​ 8,133 ​ 8,133 Two to three years ​ — ​ — ​ 30,000 ​ — ​ 8,538 ​ 38,538 Three to four years ​ — ​ — ​ — ​ — ​ 8,965 ​ 8,965 Four to five years ​ — ​ — ​ — ​ 200,000 ​ 9,412 ​ 209,412 Over five years ​ — ​ — ​ — ​ — ​ 9,882 ​ 9,882 Gross debt ​ 28,000 ​ 35,000 ​ 30,000 ​ 200,000 ​ 52,676 ​ 345,676 Unamortized debt issuance costs (1) ​ (95) ​ (159) ​ (402) ​ (6,501) ​ (2,805) ​ (9,962) Total debt ​ 27,905 ​ 34,841 ​ 29,598 ​ 193,499 ​ 49,871 ​ 335,714 Less current maturities ​ (27,905) ​ (34,841) ​ — ​ — ​ (7,746) ​ (70,492) Long-term debt ​ $ — ​ $ — ​ $ 29,598 ​ $ 193,499 ​ $ 42,125 $ 265,222 (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 ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2021 2020 2021 2020 ​ Interest expense ​ $ 5,943 ​ $ 7,179 ​ $ 12,055 $ 14,573 ​ Capitalized interest ​ — ​ — ​ — ​ (1,182) ​ Interest income ​ (24) ​ (116) ​ (83) ​ (582) ​ Net interest expense ​ $ 5,919 ​ $ 7,063 ​ $ 11,972 $ 12,809 ​

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 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 benefit are as follows (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ Six Months Ended ​ ​ ​ June 30, ​ ​ June 30, ​ ​ 2021 2020 ​ 2021 2020 ​ Taxes at U.S. statutory rate ​ $ (3,287) 21.0 % $ 1,087 21.0 % ​ $ (3,903) 21.0 % $ (6,267) 21.0 % ​ Foreign tax provision ​ (527) 3.4 ​ (2,166) (41.8) ​ ​ (1,465) 7.9 ​ (1,116) 3.7 ​ ​ CARES Act ​ — — ​ 580 11.2 ​ ​ — — ​ (5,234) 17.6 ​ ​ Subsidiary restructuring ​ — — ​ — — ​ ​ — — ​ (8,333) 27.9 ​ ​ Other (1) ​ 1,846 (11.8) ​ 228 4.4 ​ ​ 3,516 (18.9) ​ (414) 1.4 ​ ​ Income tax benefit (2) ​ $ (1,968) 12.6 % $ (271) (5.2) % ​ $ (1,852) 10.0 % $ (21,364) 71.6 % ​ (1) Includes interim period allocations of $1.6 million and $2.8 million, respectively, for the three- and six-month periods ended June 30, 2021. (2) The negative effective tax rate for the three-month period ended June 30, 2020 was driven by tax benefits of foreign losses in relation to nominal pre-tax income.

Revenue From Contracts With C_2

Revenue From Contracts With Customers (Tables)	6 Months Ended
	Jun. 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 June 30, 2021 ​ ​ ​ ​ ​ Short-term ​ $ 76,669 ​ $ 21,012 ​ $ — ​ $ — ​ $ 97,681 Long-term ​ 55,636 ​ 10,639 ​ 14,218 ​ (16,233) ​ 64,260 Total ​ $ 132,305 ​ $ 31,651 ​ $ 14,218 ​ $ (16,233) ​ $ 161,941 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended June 30, 2020 ​ ​ ​ ​ ​ Short-term ​ $ 55,368 ​ $ 36,084 ​ $ — ​ $ — ​ $ 91,452 Long-term ​ 90,473 ​ 14,752 ​ 13,593 ​ (11,123) ​ 107,695 Total ​ $ 145,841 ​ $ 50,836 ​ $ 13,593 ​ $ (11,123) ​ $ 199,147 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six months ended June 30, 2021 ​ ​ ​ ​ ​ Short-term ​ $ 125,886 ​ $ 30,419 ​ $ — ​ $ — ​ $ 156,305 Long-term ​ 140,187 ​ 23,388 ​ 30,665 ​ (25,189) ​ 169,051 Total ​ $ 266,073 ​ $ 53,807 ​ $ 30,665 ​ $ (25,189) ​ $ 325,356 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six months ended June 30, 2020 ​ ​ ​ ​ ​ Short-term ​ $ 137,692 ​ $ 58,525 ​ $ — ​ $ — ​ $ 196,217 Long-term ​ 148,801 ​ 27,569 ​ 29,134 ​ (21,553) ​ 183,951 Total ​ $ 286,493 ​ $ 86,094 ​ $ 29,134 ​ $ (21,553) ​ $ 380,168 (1) Intercompany revenues among our business segments are under agreements that are considered long-term.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 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 ​ ​ June 30, 2021 ​ June 30, 2020 ​ Income Shares Income Shares Basic: ​ ​ Net income (loss) attributable to common shareholders ​ $ (13,709) ​ ​ $ 5,450 Less: Undistributed earnings allocated to participating securities ​ — ​ ​ ​ (37) Accretion of redeemable noncontrolling interests ​ — ​ ​ ​ (69) Net income (loss) available to common shareholders, basic ​ $ (13,709) ​ 150,028 ​ $ 5,344 148,971 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted: ​ ​ ​ Net income (loss) available to common shareholders, basic ​ $ (13,709) ​ 150,028 ​ $ 5,344 148,971 Effect of dilutive securities: ​ ​ ​ Share-based awards other than participating securities ​ — ​ — ​ — 720 Net income (loss) available to common shareholders, diluted ​ $ (13,709) ​ 150,028 ​ $ 5,344 149,691 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ Six Months Ended ​ ​ June 30, 2021 ​ June 30, 2020 ​ Income ​ Income Shares Basic: ​ ​ Net loss attributable to common shareholders ​ $ (16,587) ​ ​ $ (6,488) Less: Accretion of redeemable noncontrolling interests ​ (241) ​ ​ ​ (2,155) Net loss available to common shareholders, basic ​ $ (16,828) ​ 149,982 ​ $ (8,643) 148,917 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted: ​ ​ ​ Net loss available to common shareholders, basic ​ $ (16,828) ​ 149,982 ​ $ (8,643) 148,917 Effect of dilutive securities: ​ ​ ​ Share-based awards other than participating securities ​ — ​ — ​ — — Net loss available to common shareholders, diluted ​ $ (16,828) ​ 149,982 ​ $ (8,643) 148,917
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 ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2021 2020 2021 2020 ​ Diluted shares (as reported) 150,028 149,691 149,982 148,917 ​ Share-based awards 1,325 — 1,282 980 ​ Total 151,353 149,691 151,264 149,897 ​ ​ 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 ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2021 2020 2021 2020 ​ 2022 Notes 2,519 8,997 2,519 8,997 ​ 2023 Notes 3,168 13,202 3,168 13,202 ​ 2026 Notes 28,676 — 28,676 — ​

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Schedule of grants of share-based awards	During the six-month period ended June 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 (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.

Business Segment Information (T

Business Segment Information (Tables)	6 Months Ended
	Jun. 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 ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2021 2020 ​ 2021 2020 ​ Net revenues — ​ ​ ​ ​ ​ ​ Well Intervention $ 132,305 ​ $ 145,841 ​ $ 266,073 ​ $ 286,493 ​ Robotics 31,651 ​ 50,836 ​ 53,807 ​ 86,094 ​ Production Facilities 14,218 ​ 13,593 ​ 30,665 ​ 29,134 ​ Intercompany eliminations (16,233) ​ (11,123) ​ (25,189) ​ (21,553) ​ Total $ 161,941 ​ $ 199,147 ​ $ 325,356 ​ $ 380,168 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income (loss) from operations — ​ ​ ​ ​ Well Intervention $ (6,719) ​ $ 11,758 ​ $ (1,476) ​ $ 6,066 ​ Robotics 255 ​ 7,781 ​ (2,679) ​ 4,957 ​ Production Facilities 4,682 ​ 3,365 ​ 11,196 ​ 7,008 ​ Segment operating income (loss) (1,782) ​ 22,904 ​ 7,041 ​ 18,031 ​ Goodwill impairment (1) — ​ — ​ — ​ (6,689) ​ Corporate, eliminations and other (9,159) ​ (8,710) ​ (18,537) ​ (18,175) ​ Total $ (10,941) ​ $ 14,194 ​ $ (11,496) ​ $ (6,833) ​ (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 ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2021 2020 2021 2020 ​ Well Intervention ​ $ 10,206 ​ $ 3,910 ​ $ 12,793 ​ $ 7,214 ​ Robotics ​ 6,027 ​ 7,213 ​ 12,396 ​ 14,339 ​ Total ​ $ 16,233 ​ $ 11,123 ​ $ 25,189 ​ $ 21,553 ​
Schedule of total assets by reportable segment	The following table reflects total assets by reportable segment (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2021 2020 Well Intervention ​ $ 2,084,665 ​ $ 2,134,081 Robotics ​ 101,121 ​ 132,550 Production Facilities ​ 125,863 ​ 129,773 Corporate and other ​ 106,058 ​ 101,874 Total ​ $ 2,417,707 ​ $ 2,498,278

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	6 Months Ended
	Jun. 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 ​ 48 ​ 1,304 AROs at June 30, ​ $ 28,330 ​ $ 29,562

Statement Of Cash Flow Inform_2

Statement Of Cash Flow Information (Tables)	6 Months Ended
	Jun. 30, 2021
Supplemental Cash Flow Information [Abstract]
Schedule of supplemental cash flow information	The following table provides supplemental cash flow information (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ 2021 2020 Interest paid, net of interest capitalized ​ $ 10,601 ​ $ 8,413 Income taxes paid ​ 4,588 ​ 4,937

Allowance For Credit Losses (Ta

Allowance For Credit Losses (Tables)	6 Months Ended
	Jun. 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) ​ (76) ​ 2,424 Write-offs (2) ​ ​ (1,845) ​ ​ — Adjustments (3) ​ — ​ 785 Balance at June 30, ​ $ 1,548 ​ $ 3,209 (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)	6 Months Ended
	Jun. 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ December 31, 2020 ​ ​ Principal ​ Fair ​ Principal ​ Fair ​ Amount (1) Value (2) (3) Amount (1) Value (2) (3) Term Loan (matures December 2021) ​ $ 28,000 ​ $ 27,895 ​ $ 29,750 ​ $ 28,969 Nordea Q5000 Loan (matured January 2021) (4) ​ — ​ — ​ 53,572 ​ 53,598 MARAD Debt (matures February 2027) ​ 52,676 ​ 56,542 ​ 56,410 ​ 62,318 2022 Notes (mature May 2022) ​ 35,000 ​ 35,199 ​ 35,000 ​ 33,513 2023 Notes (mature September 2023) ​ 30,000 ​ 29,662 ​ 30,000 ​ 28,650 2026 Notes (mature February 2026) ​ 200,000 ​ 247,359 ​ 200,000 ​ 211,383 Total debt ​ $ 345,676 ​ $ 396,657 ​ $ 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 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	Jun. 30, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term debt	$ 265,222	$ 258,912
Common stock	1,288,603	1,327,592
Retained earnings	456,108	464,524
Deferred tax liabilities	$ 97,906	110,821
Cumulative-effect adjustments upon adoption of ASU | Accounting Standards Update 2020-06
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) $ in Thousands	1 Months Ended	6 Months Ended
	Jun. 30, 2021USD ($)item	Jun. 30, 2021USD ($)segmentitem	Mar. 31, 2021
Segment Reporting Information [Line Items]
Number of reportable segments | segment		3
Acquisition of redeemable noncontrolling interests | $		$ 2,268
Well Intervention
Segment Reporting Information [Line Items]
Number of long-term chartered vessels | item	2	2
Robotics
Segment Reporting Information [Line Items]
Number of long-term chartered vessels | item	2	2
STL
Segment Reporting Information [Line Items]
Percentage of ownership interest			70.00%
Controlling interest acquired, ownership percentage	30.00%
Acquisition of redeemable noncontrolling interests | $	$ 2,300

Details Of Certain Accounts - O

Details Of Certain Accounts - Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Contract assets	$ 626	$ 2,446
Prepaids	12,536	15,904
Deferred costs	14,084	23,522
Income tax receivable	15,436	20,787
Other receivable	27,518	29,782
Other	8,669	9,651
Total other current assets	$ 78,869	$ 102,092

Details Of Certain Accounts -_2

Details Of Certain Accounts - Other Assets, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred recertification and dry dock costs, net	$ 19,405	$ 21,464
Deferred costs	720	861
Charter deposit	12,544	12,544
Intangible assets with finite lives, net	3,679	3,809
Other	1,070	1,335
Total other assets, net	$ 37,418	$ 40,013

Details Of Certain Accounts - A

Details Of Certain Accounts - Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll and related benefits	$ 26,907	$ 24,768
Accrued interest	6,974	7,098
Deferred revenue	9,267	8,140
Asset retirement obligations	28,330	30,913
Other	12,140	16,116
Total accrued liabilities	$ 83,618	$ 87,035

Details Of Certain Accounts -_3

Details Of Certain Accounts - Other Non-Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred revenue	$ 1,048	$ 1,869
Other	1,553	2,009
Total other non-current liabilities	$ 2,601	$ 3,878

Leases - Components Of Lease Co

Leases - Components Of Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Lease, Cost [Abstract]
Operating lease cost	$ 14,839	$ 16,106	$ 31,055	$ 32,429
Variable lease cost	3,635	3,840	7,119	7,052
Short-term lease cost	5,243	9,992	6,975	17,166
Sublease income	(329)	(328)	(678)	(607)
Net lease cost	$ 23,388	$ 29,610	$ 44,471	$ 56,040

Leases - Maturities Of Operatin

Leases - Maturities Of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Less than one year	$ 57,990	$ 60,649
One to two years	54,945	57,541
Two to three years	18,279	39,229
Three to four years	4,145	6,844
Four to five years	1,041	2,340
Over five years	4,835	4,054
Total lease payments	141,235	170,657
Less: imputed interest	(13,532)	(18,049)
Total operating lease liabilities	127,703	152,608
Current operating lease liabilities	50,769	51,599
Non-current operating lease liabilities	76,934	101,009
Vessels
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Less than one year	52,106	54,621
One to two years	49,760	52,106
Two to three years	13,557	34,580
Three to four years		2,470
Total lease payments	115,423	143,777
Less: imputed interest	(9,021)	(13,352)
Total operating lease liabilities	106,402	130,425
Current operating lease liabilities	45,940	46,748
Non-current operating lease liabilities	60,462	83,677
Facilities and Equipment
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Less than one year	5,884	6,028
One to two years	5,185	5,435
Two to three years	4,722	4,649
Three to four years	4,145	4,374
Four to five years	1,041	2,340
Over five years	4,835	4,054
Total lease payments	25,812	26,880
Less: imputed interest	(4,511)	(4,697)
Total operating lease liabilities	21,301	22,183
Current operating lease liabilities	4,829	4,851
Non-current operating lease liabilities	$ 16,472	$ 17,332

Leases - Weighted Average Remai

Leases - Weighted Average Remaining Lease Term And Discount Rate (Details)	Jun. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Weighted average remaining lease term (in years)	2 years 9 months 18 days	3 years 1 month 6 days
Weighted average discount rate (as a percent)	7.51%	7.53%

Leases - Other Information Rela

Leases - Other Information Related To Operating Leases (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Cash paid for operating lease liabilities	$ 31,562	$ 32,731
ROU assets obtained in exchange for new operating lease obligations	$ 1,500

Long-Term Debt - Maturities Of

Long-Term Debt - Maturities Of Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Less than one year	$ 70,746
One to two years	8,133
Two to three years	38,538
Three to four years	8,965
Four to five years	209,412
Over five years	9,882
Gross debt	345,676	$ 404,732
Unamortized debt issuance costs	(9,962)
Total debt	335,714
Less: current maturities	(70,492)	(90,651)
Long-term debt	265,222	258,912
Term Loan Maturing December 2021
Debt Instrument [Line Items]
Less than one year	28,000
Gross debt	28,000	29,750
Unamortized debt issuance costs	(95)
Total debt	27,905
Less: current maturities	(27,905)
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	(159)
Total debt	34,841
Less: current maturities	(34,841)
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
Two to three years	30,000
Gross debt	30,000	30,000
Unamortized debt issuance costs	(402)
Total debt	29,598
Long-term debt	29,598
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	(6,501)
Total debt	193,499
Long-term debt	193,499
MARAD Debt Maturing February 2027
Debt Instrument [Line Items]
Less than one year	7,746
One to two years	8,133
Two to three years	8,538
Three to four years	8,965
Four to five years	9,412
Over five years	9,882
Gross debt	52,676	$ 56,410
Unamortized debt issuance costs	(2,805)
Total debt	49,871
Less: current maturities	(7,746)
Long-term debt	$ 42,125

Long-Term Debt - Credit Agreeme

Long-Term Debt - Credit Agreement (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Principal amount	$ 345,676	$ 404,732
Term Loan Maturing December 2021
Debt Instrument [Line Items]
Principal amount	$ 28,000	$ 29,750
Maturity date	Dec. 31, 2021
Interest rate (as a percent)	3.35%
Frequency of periodic payment	quarterly
Periodic principal payment (as a percent)	2.50%
Term Loan Maturing December 2021 | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.25%
Term Loan Maturing December 2021 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.25%
Revolving Credit Facility Maturing December 2021
Debt Instrument [Line Items]
Borrowing capacity	$ 175,000
Additional commitments (up to)	100,000
Borrowings under Revolving Credit Facility	0
Available borrowing capacity	172,300
Letters of credit issued	$ 2,700
Commitment fee percentage	0.50%
Revolving Credit Facility Maturing December 2021 | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.50%
Revolving Credit Facility Maturing December 2021 | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.50%
Revolving Credit Facility Maturing December 2021 | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.50%
Revolving Credit Facility Maturing December 2021 | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.50%
Letter of Credit
Debt Instrument [Line Items]
Borrowing capacity	$ 25,000
Credit Agreement | Collateral Pledged
Debt Instrument [Line Items]
Maximum percent of shares of foreign subsidiaries	66.00%

Long-Term Debt - Convertible Se

Long-Term Debt - Convertible Senior Notes Due 2022 (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)$ / shares	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)$ / sharesshares	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Interest expense	$ 5,943,000	$ 7,179,000	$ 12,055,000	$ 14,573,000
Amortization of debt issuance costs			$ 1,587,000	1,619,000
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	$ 200,000		$ 200,000
Effective interest rate (as a percent)	4.80%		4.80%		7.30%
Interest expense	$ 400,000	2,300,000	$ 800,000	4,500,000
Coupon interest expense	$ 400,000	1,300,000	700,000	2,600,000
Amortization of debt issuance costs			$ 100,000
Amortization of debt discount and issuance costs		$ 1,000,000		$ 1,900,000
Convertible Senior Notes Maturing May 2022 | Minimum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			130.00%
Number of trading days			5
Number of consecutive trading days			10
Convertible Senior Notes Maturing May 2022 | Maximum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			97.00%
Number of trading days			20
Number of consecutive trading days			30

Long-Term Debt - Convertible _2

Long-Term Debt - Convertible Senior Notes Due 2023 (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)$ / shares	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)$ / sharesshares	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Interest expense	$ 5,943,000	$ 7,179,000	$ 12,055,000	$ 14,573,000
Amortization of debt issuance costs			$ 1,587,000	1,619,000
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	2,300,000	$ 700,000	4,600,000
Coupon interest expense	$ 300,000	1,300,000	600,000	2,600,000
Amortization of debt issuance costs			$ 100,000
Amortization of debt discount and issuance costs		$ 1,000,000		$ 2,000,000
Convertible Senior Notes Maturing September 2023 | Minimum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			130.00%
Number of trading days			5
Number of consecutive trading days			10
Convertible Senior Notes Maturing September 2023 | Maximum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			97.00%
Number of trading days			20
Number of consecutive trading days			30

Long-Term Debt - Convertible _3

Long-Term Debt - Convertible Senior Notes Due 2026 (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)$ / shares	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)$ / sharesshares	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Interest expense	$ 5,943,000	$ 7,179,000	$ 12,055,000	$ 14,573,000
Amortization of debt issuance costs			$ 1,587,000	$ 1,619,000
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	$ 6,500,000		$ 6,500,000
Effective interest rate (as a percent)	7.60%		7.60%		12.40%
Interest expense	$ 3,700,000		$ 7,300,000
Coupon interest expense	3,400,000		6,700,000
Amortization of debt issuance costs	$ 300,000		$ 600,000
Convertible Senior Notes Maturing February 2026 | Minimum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			130.00%
Number of trading days			5
Number of consecutive trading days			10
Convertible Senior Notes Maturing February 2026 | Maximum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			97.00%
Number of trading days			20
Number of consecutive trading days			30

Long-Term Debt - 2026 Capped Ca

Long-Term Debt - 2026 Capped Calls (Details) - 2026 Capped Calls $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)$ / sharesshares
Debt Instrument [Line Items]
Aggregate number of common shares subject to capped calls | shares	28,675,900
Initial strike price	$ 6.97
Initial cap price	$ 8.42
Aggregate cost of capped call transactions | $	$ 10.6

Long-Term Debt - MARAD Debt (De

Long-Term Debt - MARAD Debt (Details) - MARAD Debt Maturing February 2027	6 Months Ended
	Jun. 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 - Nordea Credit

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

Long-Term Debt - Components Of

Long-Term Debt - Components Of Net Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Debt Disclosure [Abstract]
Interest expense	$ 5,943	$ 7,179	$ 12,055	$ 14,573
Capitalized interest				(1,182)
Interest income	(24)	(116)	(83)	(582)
Net interest expense	$ 5,919	$ 7,063	$ 11,972	$ 12,809

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020USD ($)subsidiary
Income Tax Disclosure [Abstract]
Net tax benefit from CARES Act				$ 5.2
Current tax benefit from CARES Act				15.8
Deferred tax expense from CARES Act				$ 10.6
Number of foreign subsidiaries | subsidiary				2
Net deferred tax benefit from foreign subsidiary restructuring				$ 8.3
Effective tax rate	12.60%	(5.20%)	10.00%	71.60%

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Taxes at U.S. statutory rate	$ (3,287)	$ 1,087	$ (3,903)	$ (6,267)
Foreign tax provision	(527)	(2,166)	(1,465)	(1,116)
CARES Act		580		(5,234)
Subsidiary restructuring				(8,333)
Other	1,846	228	3,516	(414)
Income tax benefit	$ (1,968)	$ (271)	$ (1,852)	$ (21,364)
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Taxes at U.S. statutory rate	21.00%	21.00%	21.00%	21.00%
Foreign tax provision	3.40%	(41.80%)	7.90%	3.70%
CARES Act		11.20%		17.60%
Subsidiary restructuring				27.90%
Other	(11.80%)	4.40%	(18.90%)	1.40%
Income tax benefit	12.60%	(5.20%)	10.00%	71.60%
Interim period allocations	$ 1,600		$ 2,800

Revenue From Contracts With C_3

Revenue From Contracts With Customers - Disaggregation Of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Net revenues	$ 161,941	$ 199,147	$ 325,356	$ 380,168
Intercompany Eliminations
Disaggregation of Revenue [Line Items]
Net revenues	(16,233)	(11,123)	(25,189)	(21,553)
Well Intervention
Disaggregation of Revenue [Line Items]
Net revenues	132,305	145,841	266,073	286,493
Well Intervention | Intercompany Eliminations
Disaggregation of Revenue [Line Items]
Net revenues	(10,206)	(3,910)	(12,793)	(7,214)
Robotics
Disaggregation of Revenue [Line Items]
Net revenues	31,651	50,836	53,807	86,094
Robotics | Intercompany Eliminations
Disaggregation of Revenue [Line Items]
Net revenues	(6,027)	(7,213)	(12,396)	(14,339)
Production Facilities
Disaggregation of Revenue [Line Items]
Net revenues	14,218	13,593	30,665	29,134
Short-term
Disaggregation of Revenue [Line Items]
Net revenues	97,681	91,452	156,305	196,217
Short-term | Intercompany Eliminations
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Short-term | Well Intervention
Disaggregation of Revenue [Line Items]
Net revenues	76,669	55,368	125,886	137,692
Short-term | Robotics
Disaggregation of Revenue [Line Items]
Net revenues	21,012	36,084	30,419	58,525
Short-term | Production Facilities
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Long-term
Disaggregation of Revenue [Line Items]
Net revenues	64,260	107,695	169,051	183,951
Long-term | Intercompany Eliminations
Disaggregation of Revenue [Line Items]
Net revenues	(16,233)	(11,123)	(25,189)	(21,553)
Long-term | Well Intervention
Disaggregation of Revenue [Line Items]
Net revenues	55,636	90,473	140,187	148,801
Long-term | Robotics
Disaggregation of Revenue [Line Items]
Net revenues	10,639	14,752	23,388	27,569
Long-term | Production Facilities
Disaggregation of Revenue [Line Items]
Net revenues	$ 14,218	$ 13,593	$ 30,665	$ 29,134

Revenue From Contracts With C_4

Revenue From Contracts With Customers - Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract assets	$ 0.6		$ 0.6		$ 2.4
Credit losses on contract assets	0	$ 0	0	$ 0
Contract liabilities	10.3		10.3		10
Revenue recognized	4.2	3.5	5.4	6.4
Deferred contract costs	14.8		14.8		$ 24.4
Amortization of deferred contract costs	$ 9.5	$ 8.8	$ 19.9	$ 18

Revenue From Contracts With C_5

Revenue From Contracts With Customers - Remaining Performance Obligations (Details) $ in Millions	Jun. 30, 2021USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Unsatisfied performance obligations	$ 291.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Unsatisfied performance obligations	$ 152.8
Expected timing of satisfaction	6 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	$ 92
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	$ 46.6
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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic:
Net income (loss) attributable to common shareholders	$ (13,709)	$ 5,450	$ (16,587)	$ (6,488)
Less: Undistributed earnings allocated to participating securities		(37)
Less: Accretion of redeemable noncontrolling interests		(69)	(241)	(2,155)
Net income (loss) available to common shareholders, basic	$ (13,709)	$ 5,344	$ (16,828)	$ (8,643)
Weighted average number of shares outstanding, basic (in shares)	150,028	148,971	149,982	148,917
Diluted:
Net income (loss) available to common shareholders, basic	$ (13,709)	$ 5,344	$ (16,828)	$ (8,643)
Weighted average number of shares outstanding, basic (in shares)	150,028	148,971	149,982	148,917
Effect of dilutive securities:
Share-based awards other than participating securities (in shares)		720
Net income (loss) available to common shareholders, diluted	$ (13,709)	$ 5,344	$ (16,828)	$ (8,643)
Weighted average number of shares outstanding, diluted (in shares)	150,028	149,691	149,982	148,917

Earnings Per Share - Shares Inc

Earnings Per Share - Shares Included in Diluted Calculations Assuming Earnings (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Diluted shares (as reported)	150,028	149,691	149,982	148,917
Share-based awards	1,325		1,282	980
Total	151,353	149,691	151,264	149,897

Earnings Per Share - Potentiall

Earnings Per Share - Potentially Dilutive Shares Excluded From Diluted EPS Calculation (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 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	8,997	2,519	8,997
Convertible Senior Notes Maturing September 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	3,168	13,202	3,168	13,202
Convertible Senior Notes Maturing February 2026
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	28,676		28,676

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Details) $ in Millions	Jan. 04, 2021item	Jan. 31, 2021USD ($)shares	Jun. 30, 2021USD ($)shares	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)shares	Jun. 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]
Compensation cost			$ 0.9	$ 1	$ 1.7	$ 2.1
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	0.9	2.1	2
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%
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost			0.2		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	$ 2	$ 2.3
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)	Apr. 01, 2021$ / sharesshares	Jan. 04, 2021item$ / sharesshares	Jan. 01, 2021$ / sharesshares	Jan. 31, 2021
Restricted Stock Units | Management and Employee
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Date of Grant			Jan. 1, 2021
Shares/Units | shares			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 | shares		452,381
Grant Date Fair Value Per Share/Unit | $ / shares		$ 5.33
Vesting Percentage		100.00%
Vesting Date		Jan. 4, 2024
Restricted Stock | Board of Directors
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Date of Grant	Apr. 1, 2021	Jan. 4, 2021
Shares/Units | shares	9,282	14,249
Grant Date Fair Value Per Share/Unit | $ / shares	$ 5.05	$ 4.20
Vesting Percentage	100.00%	100.00%
Vesting Date	Jan. 1, 2023	Jan. 1, 2023

Business Segment Information -

Business Segment Information - Narrative (Details)	6 Months Ended
	Jun. 30, 2021segmentitem
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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Net revenues	$ 161,941	$ 199,147	$ 325,356	$ 380,168
Goodwill impairment				(6,689)
Income from operations	(10,941)	14,194	(11,496)	(6,833)
Reportable Segments
Segment Reporting Information [Line Items]
Income from operations	(1,782)	22,904	7,041	18,031
Intercompany Eliminations
Segment Reporting Information [Line Items]
Net revenues	(16,233)	(11,123)	(25,189)	(21,553)
Corporate, Eliminations and Other
Segment Reporting Information [Line Items]
Income from operations	(9,159)	(8,710)	(18,537)	(18,175)
Well Intervention
Segment Reporting Information [Line Items]
Net revenues	132,305	145,841	266,073	286,493
Well Intervention | Reportable Segments
Segment Reporting Information [Line Items]
Net revenues	132,305	145,841	266,073	286,493
Income from operations	(6,719)	11,758	(1,476)	6,066
Well Intervention | Intercompany Eliminations
Segment Reporting Information [Line Items]
Net revenues	(10,206)	(3,910)	(12,793)	(7,214)
Robotics
Segment Reporting Information [Line Items]
Net revenues	31,651	50,836	53,807	86,094
Robotics | Reportable Segments
Segment Reporting Information [Line Items]
Net revenues	31,651	50,836	53,807	86,094
Income from operations	255	7,781	(2,679)	4,957
Robotics | Intercompany Eliminations
Segment Reporting Information [Line Items]
Net revenues	(6,027)	(7,213)	(12,396)	(14,339)
Production Facilities
Segment Reporting Information [Line Items]
Net revenues	14,218	13,593	30,665	29,134
Production Facilities | Reportable Segments
Segment Reporting Information [Line Items]
Net revenues	14,218	13,593	30,665	29,134
Income from operations	$ 4,682	$ 3,365	$ 11,196	$ 7,008

Business Segment Information _3

Business Segment Information - Intercompany Segment Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Net revenues	$ (161,941)	$ (199,147)	$ (325,356)	$ (380,168)
Well Intervention
Segment Reporting Information [Line Items]
Net revenues	(132,305)	(145,841)	(266,073)	(286,493)
Robotics
Segment Reporting Information [Line Items]
Net revenues	(31,651)	(50,836)	(53,807)	(86,094)
Intercompany Eliminations
Segment Reporting Information [Line Items]
Net revenues	16,233	11,123	25,189	21,553
Intercompany Eliminations | Well Intervention
Segment Reporting Information [Line Items]
Net revenues	10,206	3,910	12,793	7,214
Intercompany Eliminations | Robotics
Segment Reporting Information [Line Items]
Net revenues	$ 6,027	$ 7,213	$ 12,396	$ 14,339

Business Segment Information _4

Business Segment Information - Total Assets By Reportable Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total assets	$ 2,417,707	$ 2,498,278
Corporate, Eliminations and Other
Segment Reporting Information [Line Items]
Total assets	106,058	101,874
Well Intervention | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	2,084,665	2,134,081
Robotics | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	101,121	132,550
Production Facilities | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	$ 125,863	$ 129,773

Asset Retirement Obligations -

Asset Retirement Obligations - Asset Retirement Obligations (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 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	48	1,304
AROs at end of period	$ 28,330	$ 29,562

Commitments And Contingencies_2

Commitments And Contingencies And Other Matters - Narrative (Details)	6 Months Ended
	Jun. 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	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Supplemental Cash Flow Information [Abstract]
Interest paid, net of interest capitalized	$ 10,601	$ 8,413
Income taxes paid	$ 4,588	$ 4,937

Statement Of Cash Flow Inform_4

Statement Of Cash Flow Information - Narrative (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Supplemental Cash Flow Information [Abstract]
Non-cash capital additions	$ 0.4	$ 1.6

Allowance For Credit Losses - A

Allowance For Credit Losses - Activities In Allowance For Credit Losses (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	$ 3,469
Additions (reductions)	(76)	$ 2,424
Write-offs	(1,845)
Balance at end of period	$ 1,548	3,209
Cumulative-effect adjustments upon adoption of ASU | 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	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount	$ 345,676	$ 404,732
Fair value	396,657	418,431
Term Loan Maturing December 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount	28,000	29,750
Fair value	27,895	28,969
Nordea Q5000 Loan Maturing 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	52,676	56,410
Fair value	56,542	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	35,199	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	29,662	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	$ 247,359	$ 211,383