Navigator (NVGS) 6-K 30 Nov 21 2021 Q2 Current report (foreign) Financial data

CoverPage

CoverPage	6 Months Ended
	Jun. 30, 2021
Document Type	6-K
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Registrant Name	NAVIGATOR HOLDINGS LTD.
Entity Central Index Key	0001581804
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets
Cash, cash equivalents and restricted cash	$ 96,356	$ 59,271
Accounts receivable, net of allowance for credit losses of $297, (December 31, 2020: $161)	20,696	14,451
Accrued income	6,797	20,073
Prepaid expenses and other current assets	17,498	22,015
Bunkers and lubricant oils	11,196	8,428
Insurance receivable	7,806	447
Amounts due from related parties	5,923	11,853
Total current assets	166,272	136,538
Non-current assets
Property, plant and equipment, net	527	502
Intangible assets, net of accumulated amortization of $341 (December 31, 2020: $279)	242	277
Investment in equity accounted joint ventures	147,211	148,665
Derivative assets	215
Right-of-use asset for operating leases	690	5,701
Prepaid expenses and other non- current assets	1,522	2,037
Total non-current assets	1,662,545	1,702,870
Total assets	1,828,817	1,839,408
Current liabilities
Current portion of secured term loan facilities, net of deferred financing costs	86,715	65,662
Current portion of operating lease liabilities	1,008	1,276
Accounts payable	8,618	8,565
Accrued expenses and other liabilities	23,676	16,488
Accrued interest	3,209	3,398
Deferred income	13,981	11,604
Amounts due to related parties	206	229
Total current liabilities	137,413	107,222
Non-current liabilities
Secured term loan facilities and revolving credit facilities, net of current portion and deferred financing costs	515,989	552,595
Senior secured bond, net of deferred financing costs	69,368	69,580
Senior unsecured bond, net of deferred financing costs	98,355	98,158
Derivative liabilities	2,943	3,007
Operating lease liabilities, net of current portion		5,232
Amounts due to related parties	57,881	61,219
Total non-current liabilities	744,536	789,791
Total Liabilities	881,949	897,013
Commitments and contingencies
Stockholders' equity
Common stock—$.01 par value per share; 400,000,000 shares authorized; 55,971,121 shares issued and outstanding, (December 31, 2020: 55,893,618)	560	559
Additional paid-in capital	593,830	593,254
Accumulated other comprehensive loss	(212)	(245)
Retained earnings	350,052	346,972
Total Navigator Holdings Ltd. stockholders' equity	944,230	940,540
Non-controlling interest	2,638	1,855
Total equity	946,868	942,395
Total liabilities and stockholders' equity	1,828,817	1,839,408
Vessels [Member]
Non-current assets
Property, plant and equipment, net	$ 1,512,138	$ 1,545,688

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowanace for doubt debts on accounts receivable current	$ 297	$ 161
Intangible assets, Accumulated amortization	$ 341	$ 279
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	400,000,000	400,000,000
Common stock, shares issued	55,971,121	55,971,121
Common stock, shares outstanding	55,893,618	55,893,618

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues
Operating revenue	$ 80,153	$ 79,869	$ 160,661	$ 161,126
Operating revenue- Luna Pool collaborative arrangement	5,546	2,596	10,786	2,596
Total operating revenues	85,699	82,465	171,447	163,722
Expenses
Brokerage commissions	974	1,305	2,167	2,560
Voyage expenses	17,689	14,728	33,305	32,272
Voyage expenses – Luna Pool collaborative arrangement	5,663	3,043	9,795	3,043
Vessel operating expenses	28,826	26,493	55,818	53,899
Depreciation and amortization	19,473	19,151	38,746	38,361
General and administrative costs	5,796	4,509	12,076	11,017
Other income	(88)	(117)	(160)	(117)
Total operating expenses	78,333	69,112	151,747	141,035
Operating income	7,366	13,353	19,700	22,687
Other income / (expense)
Foreign currency exchange gain / (loss) on senior secured bonds	330	(4,852)	338	6,565
Unrealized gain / (loss) on non-designated derivative instruments	(269)	6,354	278	(7,607)
Interest expense	(8,647)	(11,128)	(17,608)	(22,668)
Interest income	63	96	94	315
(Loss) / income before income taxes and share of result of equity accounted joint ventures	(1,157)	3,823	2,802	(708)
Income taxes	(190)	(168)	(335)	(336)
Share of result of equity accounted joint ventures	2,001	(164)	1,396	(3,205)
Net income / (loss)	654	3,491	3,863	(4,249)
Net income attributable to non-controlling interest	(394)	(483)	(783)	(905)
Net income / (loss) attributable to stockholders of Navigator Holdings Ltd.	$ 260	$ 3,008	$ 3,080	$ (5,154)
Earnings / (loss) per share attributable to stockholders of Navigator Holdings Ltd.:
Basic:	$ 0.01	$ 0.05	$ 0.06	$ (0.09)
Diluted:	$ 0.01	$ 0.05	$ 0.05	$ (0.09)
Weighted average number of shares outstanding:
Basic:	55,971,121	55,905,600	55,935,859	55,871,893
Diluted:	56,306,557	56,253,778	56,273,533	55,871,893

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - 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)	$ 654	$ 3,491	$ 3,863	$ (4,249)
Other Comprehensive income / (loss):
Foreign currency translation (loss) / gain	(48)	(11)	33	(91)
Total Comprehensive income / (loss):	606	3,480	3,896	(4,340)
Total Comprehensive income / (loss) attributable to:
Stockholders of Navigator Holdings Ltd.:	212	2,997	3,113	(5,245)
Non-controlling interest	394	483	783	905
Total Comprehensive income / (loss):	$ 606	$ 3,480	$ 3,896	$ (4,340)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Common Stock [Member]Cancelled April 14, 2020 [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]
Beginning Balance at Dec. 31, 2019	$ 939,902	$ 558		$ 592,010	$ (331)	$ 347,566	$ 99
Beginning Balance, (in shares) at Dec. 31, 2019		55,826,644
Adjustment to equity for the adoption of the new revenue standard	(151)					(151)
Restricted shares issued	1	$ 1
Restricted shares issued, (in shares)		80,794
Restricted shares cancelled			(2,144)
Net income	(4,249)					(5,154)	905
Foreign currency translation	(91)				(91)
Share-based compensation plan	538			538
Ending Balance at Jun. 30, 2020	935,950	$ 559		592,548	(422)	342,261	1,004
Ending Balance, (in shares) at Jun. 30, 2020		55,905,294
Beginning Balance at Mar. 31, 2020	932,283	$ 559		592,361	(411)	339,253	521
Beginning Balance, (in shares) at Mar. 31, 2020		55,907,438
Restricted shares cancelled			(2,144)
Net income	3,491					3,008	483
Foreign currency translation	(11)				(11)
Share-based compensation plan	187			187
Ending Balance at Jun. 30, 2020	935,950	$ 559		592,548	(422)	342,261	1,004
Ending Balance, (in shares) at Jun. 30, 2020		55,905,294
Beginning Balance at Dec. 31, 2020	$ 942,395	$ 559		593,254	(245)	346,972	1,855
Beginning Balance, (in shares) at Dec. 31, 2020	55,893,618	55,893,618
Restricted shares issued	$ 1	$ 1
Restricted shares issued, (in shares)		85,098
Restricted shares cancelled		(7,595)
Net income	3,863					3,080	783
Foreign currency translation	33				33
Share-based compensation plan	576			576
Ending Balance at Jun. 30, 2021	$ 946,868	$ 560		593,830	(212)	350,052	2,638
Ending Balance, (in shares) at Jun. 30, 2021	55,893,618	55,971,121
Beginning Balance at Mar. 31, 2021	$ 945,984	$ 560		593,552	(164)	349,792	2,244
Beginning Balance, (in shares) at Mar. 31, 2021		55,971,121
Net income	654					260	394
Foreign currency translation	(48)				(48)
Share-based compensation plan	278			278
Ending Balance at Jun. 30, 2021	$ 946,868	$ 560		$ 593,830	$ (212)	$ 350,052	$ 2,638
Ending Balance, (in shares) at Jun. 30, 2021	55,893,618	55,971,121

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net income / (loss)	$ 3,863	$ (4,249)
Adjustments to reconcile net income to net cash provided by operating activities
Unrealized (gain)/loss on non-designated derivative instruments	(278)	7,607
Depreciation and amortization	38,746	38,361
Payment of drydocking costs	(10,061)	(2,546)
Amortization of share-based compensation	577	539
Amortization of deferred financing costs	1,644	2,251
Share of result of equity accounted joint ventures, net of distributions received	(512)	3,205
Insurance claim receivable	(7,770)	(620)
Impairment of vessel	5,400	0
Changes in operating assets and liabilities
Accounts receivable	(6,245)	1,366
Bunkers and lubricant oils	(2,768)	490
Accrued income and prepaid expenses and other current assets	22,588	(9,986)
Accounts payable, accrued interest, accrued expenses and other liabilities	3,929	2,637
Amounts due to related parties	5,907	686
Net cash provided by operating activities	54,696	32,736
Cash flows from investing activities
Payments to acquire ballast water systems	(323)	(982)
Investment in equity accounted joint ventures	(4,000)	(7,500)
Distributions from equity accounted joint ventures	5,966	0
Purchase of other property, plant and equipment	(193)	(19)
Insurance recoveries	411	609
Net cash (used in) / provided by investing activities	1,861	(7,892)
Cash flows from financing activities
Proceeds from secured term loan facilities and revolving credit facilities	18,000	7,500
Issuance costs of secured bond	0	(141)
Issuance costs of secured term loan facilities	(26)	0
Issuance costs of refinancing of vessel to related parties	0	(18)
Repayment of financing of vessel to related parties	(3,342)	(3,724)
Issuance costs of Terminal Facility	0	(72)
Repayment of secured term loan facilities and revolving credit facilities	(34,104)	(33,267)
Net cash used in financing activities	(19,472)	(29,722)
Net (decrease) / increase in cash, cash equivalents and restricted cash	37,085	(4,878)
Cash, cash equivalents and restricted cash at beginning of period	59,271	66,130
Cash, cash equivalents and restricted cash at end of period	96,356	61,252
Supplemental Information
Total interest paid during the period, net of amounts capitalized	15,826	20,559
Total tax paid during the period	192	110
Senior Secured Bonds [Member]
Adjustments to reconcile net income to net cash provided by operating activities
Unrealized foreign exchange (loss)/gain	(338)	(6,565)
Other [Member]
Adjustments to reconcile net income to net cash provided by operating activities
Unrealized foreign exchange (loss)/gain	$ 14	$ (440)

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	1. Basis of Presentation​​​​​​​ The accompanying Navigator Holdings Ltd. (the “Company”), unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary for a fair presentation of the financial position of the Company and its subsidiaries as of June 30, 2021; the results of operations for the three and six months ended June 30, 2020 and 2021, the statement of stockholders’ equity for the three and six months ended June 30, 2020 and 2021, and cash flows for the six months ended June 30, 2020 and 2021. Unless the context otherwise requires, all references in the unaudited condensed consolidated financial statements to “our,” “we,” and “us” refer to the Company. The unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The accompanying unaudited condensed consolidated financial statements include the accounts of the Company, its subsidiaries and Variable Interest Entities (“VIE”) for which the Company is a primary beneficiary and are also consolidated (please read Note 16—Variable Interest Entities for additional information). All intercompany accounts and transactions have been eliminated in consolidation. A discussion of the Company’s significant accounting policies can be found in the Company’s consolidated financial statements included in the 2020 Annual Report. There have been no material changes to these policies in the six months ended June 30, 2021, apart from the below: On December 18, 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2019-12, In January 2020, the FASB issued ASU 2020-01, 2020-01 These unaudited condensed consolidated financial statements of the Company and its subsidiaries have been prepared in accordance with U.S. GAAP for interim reporting. As such, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. It is recommended that these financial statements be read in conjunction with our audited consolidated financial statements and notes thereto for the year ended December 31, 2020, included in the 2020 Annual Report. The results for the three and six months ended June 30, 2021, are not necessarily indicative of results for the year ended December 31, 2021 or any other future periods. Recent Accounting Pronouncements In March 2020, the FASB issued ASU 2020-04, 2020-04 In August 2020, the FASB issued ASU 2020-06, 470-20) 815-40)”,

Revenue Recognition

Revenue Recognition	6 Months Ended
	Jun. 30, 2021
Revenue Recognition [Abstract]
Revenue Recognition	2. Revenue Recognition The Company receives its revenue streams from three different sources; vessels on time charters (which are accounted for as leases under Topic 842); voyage charters; and contracts of affreightment (“COA”) accounted for under Topic 606. Revenues from the Luna Pool collaborative arrangement are accounted for under ASC 808. Time charter revenue is payable monthly in advance whilst revenue from voyage charters and COAs is due upon discharge of the cargo at the discharge port. In the case of voyage charters, the vessel is contracted for a voyage, or a series of voyages, between two or more ports and the Company is paid for the cargo transported. Revenue from COAs is recognized on the same basis as revenue from voyage charters, as they are essentially a series of consecutive voyage charters. Payment from voyage charters and COAs is due upon discharge of the cargo at the discharge port. Since January 1, 2018, following adoption of ASU No. 2014-09, Under this revenue recognition standard, the Company has identified certain costs incurred to fulfill a contract with a charterer, which are costs incurred following the commencement of a contract or charter party but before the loading of the cargo commences. These directly related costs are generally fuel or any canal or port costs incurred to get the vessel from its position at inception of the contract to the load port to commence loading of the cargo. These costs are deferred and amortized over the duration of the performance obligation on a time basis. Voyage charters and COAs have an expected duration of one year or less. The Company has applied optional exemptions on adoption of the revenue standard, as set out in Topic 606-10-50-14 In addition, accrued income relates to our conditional right to consideration for our completed performance under contracts and is recognized according to our performance. Contract liabilities or deferred income includes payments received in advance of performance under contracts and is recognized when performance under the respective contract has been completed. For vessels contracted under time charters, the arrangements are for a specified period of time. The Company receives a fixed charter rate per on-hire add-on Operating revenues The following table compares our operating revenues by the source of revenue stream for the three and six months ended June 30, 2020 and 2021: Three months ended June 30, (in thousands) Six months ended June 30, (in thousands) 2020 2021 2020 2021 Operating revenues: Time charters $ 43,146 $ 41,903 $ 93,841 $ 84,582 Time charters from Luna Pool collaborative arrangement — 930 — 1,279 Voyage charters 36,723 38,250 67,285 76,079 Voyage charters from Luna Pool collaborative arrangement 2,596 4,616 2,596 9,507 Total operating revenues $ 82,465 $ 85,699 $ 163,722 $ 171,447 Voyage Charter revenues Voyage charter revenues, which include revenues from contracts of affreightment, are shown net of address commissions. As of June 30, 2021, for voyage charters and contracts of affreightment, services accounted for under Topic 606, the amount of contract assets reflected within accrued income on the Company’s unaudited condensed consolidated balance sheets was $3.0 million (December 31, 2020: $11.4 million). Changes in the contract asset balance at the balance sheet dates reflect income accrued after loading of the cargo commences but before an invoice has been raised to the charterer, as well as changes in the number of the Company’s vessels contracted under voyage charters or contracts of affreightment. The amount of contract liabilities reflected within deferred income on the Company’s unaudited condensed consolidated balance sheets was $1.4 million as of June 30, 2021 (December 31, 2020: $1.6 million). The opening and closing balance of receivables from voyage charters, including contracts of affreightment, was $3.3 million and $8.3 million, respectively, as of June 30, 2021 (December 31, 2020: $4.2 million and $3.3 million, respectively) and is reflected within net accounts receivable on the Company’s unaudited condensed consolidated balance sheets. The amount allocated to costs incurred to fulfill a contract with a charterer, which are costs incurred following the commencement of a contract or charter party but before the loading of the cargo commences, was $1.0 million as of June 30, 2021 (December 31, 2020: $1.5 million) and is reflected within prepaid expenses and other current assets on the Company’s unaudited condensed consolidated balance sheets. Time charter revenues: As of June 30, 2021, 20 of the Company’s 38 vessels were subject to time charters, fifteen of which will expire within one year, three of which will expire within three years and two which will expire after more than five years from the balance sheet date. (December 31, 2020: 19 of the Company’s 38 vessels, were subject to time charters, eleven of which will expire within one year, six which will expire within three years, and two which will expire after more than five years from the balance sheet date). The estimated undiscounted cash flows for committed time charter revenues expected to be received on an annual basis for ongoing time charters, as of each June 30, is as follows: (in thousands) Within 1 year: $ 143,372 2 years: $ 53,346 3 years: $ 32,649 4 years: $ 21,480 5 years: $ 21,480 More than 5 years: $ 16,152 For time charter revenues accounted for under Topic 842, the amount of accrued income on the Company’s unaudited condensed consolidated balance sheets as of June 30, 2021 was $3.6 million (December 31, 2020: $8.4 million). The amount of hire payments received in advance under time charter contracts, recognized as a liability and reflected within deferred income on the Company’s unaudited condensed consolidated balance sheets as of June 30, 2021, was $12.5 million (December 31, 2020: $10.0 million). Deferred income allocated to time charters will be recognized ratably over time, which is expected to be within one month from June 30, 2021. Revenues from Luna Pool collaborative arrangement Revenues from the Luna Pool collaborative arrangement for the three and six months ended June 30, 2021, which are accounted for under ASC 808 – Collaborative Arrangements, represent our share of pool net revenues generated by the other Pool Participant’s vessels in the Luna Pool. These include revenues from voyage charters and contract of affreightment, which are accounted for under Topic 606, in addition to revenues from time charters, which are accounted for under Topic 842. Please read Note 5— Investment in Equity Accounted Joint Ventures for additional information. The Pool Participants manage and participate in the activities of the Luna Pool through an executive committee comprising equal membership from both Pool Participants. Certain decisions made by the executive committee as to the operations of the Luna Pool require the unanimous agreement of both participants with others requiring a majority of votes. At this time we control 66% of the votes. The Company’s wholly owned subsidiary, NGT Services (UK) Limited acts as commercial manager (“Commercial Manager”) to the Luna Pool. Under the pool agreement, the Commercial Manager is responsible, as agent, for the marketing and chartering of the participating vessels, collection of revenues and paying voyage costs such as port call expenses, bunkers and brokers’ commissions in relation to charter contracts, but the vessel owners continue to be fully responsible for the financing, insurance, crewing and technical management of their respective vessels. The Commercial Manager receives a fee based on the net revenues of the Luna Pool, which is levied on the Pool Participants. The portion of the Commercial Manager’s fee which is due from the other Pool Participant was a net amount of $0.1 million and $0.2 million, after the elimination of inter group income, for the three and six months ended June 30, 2021 respectively, and is presented as other income within our unaudited condensed consolidated statements of operations. The Luna Pool became operational during the second quarter of 2020 and consequently the other income for both the three and six months ended June 30, 2020 was $0.1 million. Pool revenues and expenses within the Luna Pool are accounted for in accordance with ASC 808 – Collaborative Arrangements, when two (or more) parties are active participants in the arrangement and exposed to significant risk and rewards dependent on the commercial success of the activity. Pool earnings (gross earnings of the pool less costs and overheads of the Luna Pool and fees to the Commercial Manager) are aggregated and then allocated to the Pool Participants in accordance with an apportionment for each participant’s vessels multiplied by the number of days each of their vessels are on hire in the pool during the relevant period and therefore the Company is exposed to risk and rewards dependent on the commercial success of the Luna Pool. We have concluded that the Company is an active participant due to its representation on the executive committee and the participation of the Commercial Manager, as is the other Pool Participant. We have presented our share of net income earned under the Luna Pool collaborative arrangement across a number of lines in our unaudited condensed consolidated statements of operations. Our share of pool net revenues generated by the other Pool Participant’s vessels in the Luna Pool collaborative arrangement amounted to $5.6 million and $10.8 million for the three and six months ended June 30, 2021, respectively, and is presented on the face of our unaudited condensed consolidated statements of operations within operating revenues – Luna Pool collaborative arrangement. The other Pool Participant’s share of pool net revenues generated by our vessels in the pool amounted to $5.7 million and $9.8 million for the three and six months ended June 30, 2021, respectively, and is presented on the face of our unaudited condensed consolidated statements of operations within voyage expenses – Luna Pool collaborative arrangement. The Luna Pool became operational during the quarter ended June 30, 2020 and consequently the impact on the Company’s consolidated statements of operations for both the three and six months ended June 30, 2020 was operating revenues from Luna Pool collaborative arrangement of $2.6 million, and voyage expenses from Luna Pool collaborative arrangement of $3.0 million.

Current Expected Credit Losses

Current Expected Credit Losses	6 Months Ended
	Jun. 30, 2021
Credit Loss [Abstract]
Current Expected Credit Losses	3. Current Expected Credit Losses In June 2016, FASB issued ASU 2016-13, held-to-maturity Using the modified retrospective method, reporting periods beginning after January 1, 2020, are presented under Topic 326 while comparative periods continue to be reported in accordance with previously applicable GAAP and have not been restated. The adoption of Topic 326 did not have a material impact on our consolidated financial statements. The total provision on transition was $0.1 million and has been presented as an adjustment to equity in the unaudited condensed consolidated statements of stockholders’ equity. For the amounts calculated for the Current Expected Credit Loss (“CECL”) model for the year ended December 31, 2020, since transition, the Company has recognized an expense in our unaudited condensed consolidated statements of operations. As the amount is immaterial, it is presented within general and administration costs rather than a separate line. For financial assets measured at amortized cost within the scope of Topic 326, we have separately presented on the statement of financial position the allowance for credit losses as a contra-asset that is deducted from the asset’s amortized cost basis. Management has assessed the financial assets that fall under the scope of the new standard and have determined how to apply the model to each one. Cash, cash equivalents and restricted cash as insurance debtor amounts are considered to have negligible risk of loss based on consideration of whether the balances have short-term maturities and whether the counterparty has an investment grade credit rating, limiting any credit exposure, and as such no impairment allowance has been recognized. Trade receivables are presented net of allowances for doubtful debt based on observable events and expected credit losses. At each balance sheet date, all potentially uncollectible accounts are assessed individually for the purpose of determining the appropriate provision for doubtful accounts. The expected credit loss allowance is calculated using loss rates which reflect similar risk characteristics. Management have considered that trade receivables should be split into two pools with similar risk characteristics. Pool 1 consists of freight and recharge receivables for which management have made estimates of losses based on an aging matrix. Pool 2 consists of demurrage receivables where the percentage historical recovery/loss data over the last five years is utilized to model an estimate of expected credit losses. Our trade receivables have short maturities so we have considered that forecasted changes to economic conditions will have an insignificant effect on the estimate of the allowance, except in extraordinary circumstances. Contract assets have been deemed as being at remote risk as there have been no historical contract assets recognized which were not subsequently invoiced to customers and paid. The risk of expected losses for these assets is deemed to be remote and an appropriate percentage of expected losses has been applied to the whole balance. The activity in the allowance for credit losses for financial assets within the scope of ASU 2016-13 (in thousands) Balance as at December 31, 2019 $ — Allowance recognized on transition 151 Provision for expected credit losses during 2020 10 Balance as at December 31, 2020 $ 161 Current period provision for expected credit losses 136 Balance as at June 30, 2021 $ 297 In November 2018, the FASB issued ASU 2018-19, 2016-13, In April 2019, the FASB issued ASU 2019-04, 2019-04 2019-04 2019-04 In May 2019, the FASB issued ASU 2019-05, 2016-13. 2019-05 2016-13 2016-13, 326-20, 825-20 held-to-maturity 2019-05 2016-13. 2016-13 2019-05 In May 2019, the FASB issued ASU 2019-11, credit-deteriorated 2019-11 2016-13. 2016-13 2019-11

Vessels, net

Vessels, net	6 Months Ended
	Jun. 30, 2021
Vessels, net	4. Vessels, net Vessel Drydocking Total (in thousands) Cost December 31, 2020 $ 2,062,513 $ 39,654 $ 2,102,167 Additions 323 10,061 10,384 Impairment following vessel damage (17,000 ) — (17,000 ) Write-offs of fully amortized assets — (6,576 ) (6,576 ) June 30, 2021 $ 2,045,836 $ 43,139 $ 2,088,975 Accumulated Depreciation December 31, 2020 $ 536,436 $ 20,043 $ 556,479 Charge for the period 34,018 4,516 38,534 Impairment following vessel damage (11,600 ) — (11,600 ) Write-offs of fully amortized assets — (6,576 ) (6,576 ) June 30, 2021 $ 558,854 $ 17,983 $ 576,837 Net Book Value December 31, 2020 $ 1,526,077 $ 19,611 $ 1,545,688 June 30, 2021 $ 1,486,982 $ 25,156 $ 1,512,138 On June 10, 2021, Navigator Neptune The cost and net book value of the 20 vessels that were contracted under time charter arrangements (please read Note 2—Revenue Recognition for additional information) was $1,167 million and $895 million, respectively, as of June 30, 2021 (December 31, 2020: $1,084 million and $839 million, respectively, for 19 vessels contracted under time charters). The net book value of vessels that serve as collateral for the Company’s secured bond, secured term loan and revolving credit facilities (please read Note 6—Secured Term Loan Facilities and Revolving Credit Facilities; and Note 7—Senior Secured Bond for additional information) was $1,331 million as of June 30, 2021 (December 31, 2020: $1,359 million). The cost and net book value of vessels that are included in the table above and are subject to financing arrangements (please read Note 16—Variable Interest Entities for additional information) was $83.5 million and $70.9 million, respectively, as of June 30, 2021. (December 31, 2020: $82.9 million and $71.0 million, respectively).

Investment in Equity Accounted

Investment in Equity Accounted Joint Venture	6 Months Ended
	Jun. 30, 2021
Equity Method Investments and Joint Ventures [Abstract]
Investment in Equity Accounted Joint Venture	5. Investment in Equity Accounted Joint Ventures Interests in joint ventures are accounted for using the equity method and are recognized initially at cost and subsequently include the Company’s share of the profit or loss and other comprehensive income of equity-accounted As at December 31, 2020 and June 30, 2021, we had the following participation in investments that are accounted for using the equity method: December 31, June 30, Enterprise Navigator Ethylene Terminal L.L.C. (“Export Terminal Joint Venture”) 50 % 50 % Luna Pool Agency Limited. (“Pool Agency”) 50 % 50 % Export Terminal Joint Venture In January 2018, the Company announced the execution of definitive agreements creating a 50/50 joint venture with Enterprise Products Partners L.P. (the “Export Terminal Joint Venture”) to construct and operate an ethylene export marine terminal at Morgan’s Point, Texas on the Houston Ship Channel (the “Marine Export Terminal”). Enterprise Products Partners, L.P. is the sole managing member of the Export Terminal Joint Venture, and it is also the operator of the Marine Export Terminal. Interests in joint ventures are accounted for using the equity method. They are recognized initially at cost, which includes capitalized interest. The capitalized interest will be amortized over the useful life of the terminal. Subsequent to initial recognition, the consolidated financial statements will include the Company’s share of the profit or loss and other comprehensive income (“OCI”) of equity-accounted investees, until the date on which joint control ceases. The Export Terminal Joint Venture is organized as a limited liability company and maintains separate ownership accounts, consequently we account for our investment using the equity method as our ownership interest is 50% and we exercise joint control over the investee’s operating and financial policies. We disclose our proportionate share of profits and losses from equity method unconsolidated affiliates in the statement of operations and adjust the carrying amount of our equity method investments on the balance sheet accordingly. Subsequent to initial recognition, the consolidated financial statements includes the Company’s share of the profit or loss and other comprehensive income (“OCI”) of equity-accounted investees, until the date on which joint control ceases. As of June 30, 2021, we had contributed to the Export Terminal Joint Venture all of our 50% share of the$146.5 million capital cost for the construction of the Marine Export Terminal. On January 21, 2021, we made afinal capital contribution of $4.0 million by drawing down on the Terminal Facility. The table below represents the Company’s investment into the Export Terminal Joint Venture, pursuant to which the Company has a 50% economic interest in building and operating the Marine Export Terminal, as of December 31, 2020 and June 30, 2021: 2020 2021 (in thousands) Investment in equity accounted joint venture at January 1 $ 130,660 $ 148,665 Equity contributions to joint venture entity 17,000 4,000 Share of results 651 1,396 Distributions received from joint venture entity — (6,850 ) Capitalized interest and deferred financing costs 354 — Total investment in equity accounted joint venture at December 31 and June 30 $ 148,665 $ 147,211 Cumulative interest capitalized on the investment in the Export Terminal Joint Venture are being amortized over the estimated useful life of the Marine Export Terminal, which began commercial operations with the export of commissioning cargoes in December 2019. As of June 30, 2021, the unamortized difference between the carrying amount of the investment in the Export Terminal Joint Venture and the amount of the Company’s underlying equity in net assets of the Export Terminal Joint Venture, was $6.3 million (December 31, 2020: $6.5 million). The costs amortized in the six months ended June 30, 2021 were $0.1 million (six months ended June 30, 2020: $0.1 million) and are presented in the share of result of the equity accounted joint ventures within the unaudited condensed consolidated statement of operations. The Company has made an accounting policy election to apply the cumulative earnings approach outlined in ASC 230 – Statement of Cash Flows (“Topic 230”) to determine whether dividend distributions received from equity method investees are returns on investment or returns of investment and should be classified as cash flows from operating activities or investing activities respectively. Under the cumulative earnings method, we compare the cumulative distributions received to our cumulative equity in earnings from the investee, as adjusted for amortization of basis differences. We analyze dividends received in interim periods on a quarter-by-quarter During the six months ended June 30, 2021, we received dividend distributions from the Export Terminal Joint Venture of $6.9 million, of which $6.0 million is in excess of our cumulative equity in earnings and is presented as cash flows from investing activities and $0.9 million is presented as cash flows from operating activities within the unaudited condensed consolidated statements of cash flows. No dividend distributions were received for the six months ended June 30, 2020 or for the year ended December 31, 2020. Equity method earnings, excluding amortized costs, of $2.1 million and $1.5 million for the three and six months ended June 30, 2021 respectively, were recognized in the share of result of equity accounted joint ventures within the unaudited condensed consolidated statement of operations (three and six months ended June 30, 2020: losses of $0.1 million and $3.0 million and respectively). Impairment of Joint Venture The equity method investment is reviewed for indicators of impairment when events or circumstances indicate the carrying amount of the investment may not be recoverable. When such indicators are present, we determine if the indicators are ‘other than temporary’ to determine if an impairment exists. If we determine that an impairment exists, a discounted cash flow analysis is carried out based on the future cash flows expected to be generated over the investment’s estimated remaining useful life. The resulting net present value is compared to the carrying value and we would recognize an impairment loss equal to the amount by which the carrying amount exceeds its fair value. Considerations in identifying if indicators of impairment are present for the equity method investment include significant incidents that have resulted in the forecast future operating cash flows to be amended, such as significant market events that impact the terminal operations and cashflow, physical damage to assets, recurring financial losses for consecutive periods or changes to the Company’s equity holding in the investment. As of June 30, 2021, the aggregate carrying value of our investment in the Export Terminal Joint Venture was $147.2. million (December 31, 2020: $148.7 million). We believe that there are no events or circumstances that indicate that the value of the investment in the Export Terminal Joint Venture should be impaired as of June 30, 2021. Accordingly, no impairment charge has been recorded as of June 30, 2021 following the requirements of our U.S. GAAP impairment accounting policy. Pool Agency In March 2020, the Company collaborated with Pacific Gas Pte. Ltd. and Greater Bay Gas Co. Ltd. to form and manage the Luna Pool. We refer to the Company and Greater Bay Gas Co. Ltd. collectively as the “Pool Participants”. As part of the formation of the Luna Pool, a new entity, Luna Pool Agency Limited, (“Pool Agency”) was established in May 2020. The pool participants jointly own the Pool Agency on an equal basis, and both have equal board representation. The investment in the Pool Agency created a 50/50 joint venture with Greater Bay Gas Co. Ltd. as outlined by Accounting Standards Codification (“ASC”) 323 – Investments -Equity Method and Joint Ventures (“ASC 323”). The Company’s investment in the Pool Agency is accounted for as an equity investment in accordance with the guidance within ASC 810 – Consolidation and ASC 323. Therefore, we account for our investment using the equity method as our ownership interest is 50% and we exercise joint control over the entity’s operating and financial policies. As of June 30, 2021 and December 31, 2020, we have recognized the Company’s initial investment of one British pound in the Pool Agency within investments in equity accounted joint ventures on our unaudited condensed consolidated balance sheets. The Pool Agency has no activities other than that as a legal custodian of the Luna Pool bank account and there will be no variability in its financial results, as it has no income and its minimal operating expenses are reimbursed by the Pool Participants.

Secured Term Loan Facilities an

Secured Term Loan Facilities and Revolving Credit Facilities	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Secured Term Loan Facilities and Revolving Credit Facilities	6. Secured Term Loan Facilities and Revolving Credit Facilities Terminal Facility In March 2019 On May 6, 2021, the Company obtained a waiver from the lenders under the Terminal Facility, which is retrospective with effect from the date of its inception, to correct a technical inconsistency in the Terminal Facility, involving a restrictive covenant relating to taking affirmative action regarding the treatment of tax status of the borrower as a corporation for U.S. federal, state or local income tax purposes. The waiver required among other things, an amendment to the credit agreement and other loan documentation to remediate the inconsistency and to set aside and fund a tax reserve, based on the subsequent three months’ tax liabilities. The terms of the waiver were complied with and the amendment entered into on August 4, 2021. The following table shows the breakdown of all secured term loan facilities and total deferred financing costs split between current and non-current December 31, June 30, (in thousands) Current Liability Current portion of secured term loan facilities $ 67,936 $ 89,056 Less: current portion of deferred financing costs (2,274 ) (2,341 ) Current portion of secured term loan facilities, net of deferred financing costs $ 65,662 $ 86,715 Non-Current Secured term loan facilities and revolving credit facilities net of current portion* $ 617,994 $ 577,427 Less: non-current (4,183 ) (3,553 ) Non-current non-current $ 613,811 $ 573,874 * Includes amounts relating to the Navigator Aurora Facility held within a lessor entity (for which legal ownership resides with a financial institution) that we are required to consolidate under U.S. GAAP into our financial statements as a variable interest entity.

Senior Secured_Unsecured Bond

Senior Secured/Unsecured Bond	6 Months Ended
	Jun. 30, 2021
Senior Secured/Unsecured Bond	8. Senior Unsecured Bond In September 2020, the Company issued senior unsecured bonds in an aggregate principal amount of $100.0 million with Nordic Trustee AS as the bond trustee (the “2020 Bonds”). The net proceeds of the issuance of the 2020 Bonds were used to redeem in full all of our outstanding 2017 Bonds which were due to mature in full on February 10, 2021 and become repayable on that date. The 2020 Bonds are governed by Norwegian law and listed on the Nordic ABM which is operated and organized by Oslo Børs ASA. The 2020 Bonds bear interest at a rate of 8.0% per annum and mature on September 10, 2025. Interest is payable semi-annually in arrears on March 10 and September 10. The 2020 Bonds are redeemable by the Company, in whole or in part, at any time. Any 2020 Bonds redeemed; up until September 9, 2023 will be priced at the aggregate of the net present value of 103.2% of par and interest payable up to September 9, 2023; from September 10, 2023 up until September 9, 2024, are redeemable at 103.2% of par; from September 10, 2024 up until March 9, 2025, are redeemable at 101.6% of par, and from March 10, 2025 to the maturity date are redeemable at 100% of par, in each case, in cash plus accrued interest.​​​​​​​ Additional financial covenants (each as defined within the bond agreement governing the 2020 Bonds (the “2020 Bond Agreement”)) are: (a) The issuer shall ensure that the Group (meaning “the Company and its subsidiaries”) maintains a minimum liquidity of no less than $35.0 million; and (b) maintain a Group equity ratio (as defined in the 2020 Bond Agreement) of at least 30%. As of June 30, 2021, the Company was in compliance with all covenants for the 2020 Bonds​​​​​​​.​​​​​​​ The 2020 Bond Agreement provides that we may declare or pay dividends to shareholders provided that the Company maintains a minimum liquidity of $ 60.0 The following table shows the breakdown of our senior unsecured bond and total deferred financing costs as of December 31, 2020 and June 30, 2021: December 31, June 30, 2021 (in thousands) Senior Unsecured Bond Total Bond $ 100,000 $ 100,000 Less deferred financing costs (1,842 ) (1,645 ) Total Bond, net of deferred financing costs $ 98,158 $ 98,355
2018 Senior Secured Bonds [Member]
Senior Secured/Unsecured Bond	7. Senior Secured Bond In November 2018, the Company issued senior secured bonds in an aggregate principal amount of NOK 600 million with Nordic Trustee AS as the bond trustee (the “2018 Bonds”). The net proceeds were used to partially finance our portion of the capital cost for the construction of the Marine Export Terminal. The 2018 Bonds are governed by Norwegian law and are listed on the Nordic ABM which is operated and organized by Oslo Børs ASA. The 2018 Bonds bear interest at a rate equal to the 3-month 360-day On the same date, the Company entered into a cross-currency interest rate swap agreement with Nordea Bank Abp (“Nordea”), with a termination date of November 2, 2023, to run concurrently with the 2018 Bonds. The interest rate payable by the Company under this cross-currency 3-month The Company may redeem the 2018 Bonds, in whole or in part, at any time beginning on or after November 2, 2021. Any 2018 Bonds redeemed from November 2, 2021 until November 1, 2022, are redeemable at 102.4% of par, from November 2, 2022 until May 1, 2023, are redeemable at 101.5% of par, and from May 2, 2023 to the maturity date are redeemable at 100% of par, in each case, in cash plus accrued interest.​​​​​​​ Additionally, upon the occurrence of a “Change of Control Event” (as defined in the 2018 Bond Agreement), the holders of 2018 Bonds have an option to require us to repay such holders’ outstanding principal amount of 2018 Bonds at 101% of par, plus accrued interest. The financial covenants each as defined within the 2018 Bond Agreement are: (a) The issuer shall ensure that the Group (meaning “the Company and its subsidiaries”) maintains a minimum liquidity of no less than $25.0 million and (b) maintain a Group equity ratio of at least 30% (as defined in the 2018 Bond Agreement). At June 30, 2021, the Company was in compliance with all covenants for the 2018 Bonds.​​​​​​​ The 2018 Bond Agreement provides that we may declare dividends not exceeding 50% of our cumulative consolidated net profits after taxes from January 1, 2020. The 2018 Bond Agreement also limits us and our subsidiaries from, among other things, entering into mergers and divestitures, engaging in transactions with affiliates or incurring any additional liens which would have a material adverse effect. In addition, the 2018 Bond Agreement includes customary events of default, including those relating to a failure to pay principal or interest, a breach of covenant, false representation and warranty, a cross-default to other indebtedness, the occurrence of a material adverse effect, or our insolvency or dissolution. The following table shows the breakdown of our senior secured bond and total deferred financing costs as of December 31, 2020 and June 30, 2021: December 31, June 30, (in thousands) Senior Secured Bond Total Bond $ 70,299 $ 69,961 Less deferred financing costs (719 ) (593 ) Total Bond, net of deferred financing costs $ 69,580 $ 69,368

Derivative Instruments Accounte

Derivative Instruments Accounted for at Fair Value	6 Months Ended
	Jun. 30, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments Accounted for at Fair Value	9. Derivative Instruments Accounted for at Fair Value The Company uses derivative instruments in accordance with its overall risk management policy to mitigate our risk to the effects of unfavorable fluctuations in foreign exchange and interest rate movements. The Company held no derivatives designated as hedges as of December 31, 2020 and June 30, 2021. Fair value is a market-based Level 1—Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2—Include other inputs that are directly or indirectly observable in the marketplace. Level 3—Unobservable inputs which are supported by little or no market activity. On July 2, 2020, the Company entered into floating-to-fixed 3-month 360-day 360-day The interest rate swaps are remeasured to fair value at each reporting date and have been categorized as level two on the fair value measurement hierarchy. The fair value of these non-designated non-current non-current non-designated The Company entered into a cross-currency interest rate swap agreement concurrently with the issuance of its NOK denominated senior secured bonds (please read Note 7—Senior Secured Bond for additional information) and pursuant to this swap, the Company receives the principal amount of NOK 600 million in exchange for a payment of a fixed amount of $71.7 million on the maturity date of the swap. In addition, at each quarterly interest payment date, the cross-currency interest rate swap exchanges a receipt of floating interest of 6.0% plus 3-month 3-month The cross-currency interest rate swap is remeasured to fair value at each reporting date and has been categorized as level two on the fair value measurement hierarchy. The fair value of this non-designated non-current non-designated The remeasurement to fair value has no impact on the cash flows at the reporting date. Amounts included in restricted cash represent those required to be set aside as collateral by a contractual agreement with a banking institution for the forecast future liability on the cross-currency interest rate swap agreement at the reporting date. The Company has not offset the fair value of the derivative with the cash collateral account notwithstanding there is a master netting agreement in place. Please read Note 15—Cash, Cash Equivalents and Restricted Cash for additional information. The fair values of our interest rate swap agreements and the cross-currency interest rate swap is the estimated amount that we would pay to sell or transfer the swap at the reporting date, taking into account current interest rates and the current credit worthiness of the swap counterparties, in addition to foreign exchange rates for the cross-currency swap agreement. The estimated amount is the present value of future cash flows, adjusted for credit risk. The Company transacts all of these derivative instruments through investment-grade rated financial institutions at the time of the transaction. It is possible that the amount recorded as a derivative asset or liability could vary by a material amount in the near term if there is volatility in the credit markets or if credit risk were to change significantly. The fair value of our interest rate swap agreements and cross-currency long-term The following table includes the estimated fair value of those assets and liabilities that are measured at fair value on a recurring basis and are carried at fair value as at December 31, 2020 and June 30, 2021: December 31, 2020 June 30, 2021 Fair Value Hierarchy Level Fair Fair Fair (in thousands) Cross-currency interest rate swap agreement Level 2 (2,896 ) (2,943 ) Interest rate swap agreements Level 2 (111 ) 215

Fair Value of Financial Instrum

Fair Value of Financial Instruments Not Accounted For at Fair Value	6 Months Ended
	Jun. 30, 2021
Investments, All Other Investments [Abstract]
Fair Value of Financial Instruments Not Accounted For at Fair Value	10. Fair Value of Financial Instruments Not Accounted for at Fair Value The principal financial assets of the Company at June 30, 2021 and December 31, 2020 consist of cash, cash equivalents, and restricted cash and accounts receivable. The principal financial liabilities of the Company as of June 30, 2021 and December 31, 2020 consist of accounts payable, accrued expenses and other liabilities, secured term loan facilities, revolving credit facilities, the 2020 Bonds and the 2018 Bonds. The carrying values of cash, cash equivalents and restricted cash, accounts receivable, accounts payable, accrued expenses and other liabilities are reasonable estimates of their fair value due to the short-term nature or liquidity of these financial instruments. Fair value is a market-based Level 1—Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2—Include other inputs that are directly or indirectly observable in the marketplace. Level 3—Unobservable inputs which are supported by little or no market activity. The 2020 Bonds and the 2018 Bonds are classified as a level two liability and the fair values have been calculated based on the most recent trades of the bond on the Oslo Børs prior to June 30, 2021. These trades are infrequent and therefore not considered to be an active market. The 2018 Bonds are denominated in Norwegian Kroner (“NOK”) and the fair value has been translated to the functional currency of the Company using the prevailing exchange rate as at June 30, 2021 and December 31, 2020. The fair value of secured term loan facilities and revolving credit facilities is estimated to approximate the carrying value in the balance sheet since they bear a variable interest rate, which is reset on a quarterly basis. This has been categorized at level two on the fair value measurement hierarchy as at June 30, 2021. The following table includes the estimated fair value and carrying value of those assets and liabilities where the fair value does not approximate to carrying value. The table excludes cash, cash equivalents, restricted cash, accounts receivable, accounts payable, secured term loan facilities and revolving credit facilities, accrued expenses and other liabilities because the fair value approximates carrying value and, for accounts receivable and payable, are due in one year or less. December 31, 2020 June 30, 2021 Financial Asset/Liability Fair Carrying Fair Value Carrying Fair Value (in thousands) 2018 Bonds (note 7) Level 2 (70,299 ) (72,672 ) (69,691 ) (72,759 ) 2020 Bonds (note 8) Level 2 (100,000 ) (103,500 ) (100,000 ) (105,000 )

Earnings per Share

Earnings per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Earnings per Share	11. Earnings per share Basic earnings per share is calculated by dividing the net income/(loss) available to common shareholders by the average number of common shares outstanding during the periods. Diluted earnings per share is calculated by adjusting the weighted average number of common shares used for calculating basic earnings per share for the effects of all potentially dilutive shares. The following table shows calculation of both basic and diluted number of weighted average outstanding shares for the three and six months ended June 30, 2020 and 2021: Three months ended Six months ended 2020 2021 2020 2021 Basic and diluted income / (loss) available to common stockholders (in thousands) $ 3,008 $ 260 $ (5,154 ) $ 3,080 Basic weighted average number of shares: 55,905,600 55,971,121 55,871,893 55,935,859 Effect of dilutive potential share options*: 348,178 335,436 — 337,674 Diluted weighted average number of shares 56,253,778 56,306,557 55,871,893 56,273,533 * Due to a loss for the six months ended June 30, 2020, no incremental shares are included because the effect would be antidilutive. The number of potential dilutive shares excluded from the calculation for the six months ended June 30, 2020 is 349,057.

Share-Based Compensation

Share-Based Compensation	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	12. Share-Based Compensation On March 17, 2021, the Company granted 29,240 restricted shares under the Navigator Holdings Ltd. 2013 Long-Term Incentive Plan (the “2013 Plan”) to non-employee In March 2021, 30,380 shares that were previously granted to non-employee During the six months ended June 30, 2021, 7,595 shares awarded to a non-employee On March 19, 2020, the Company granted 37,975 restricted shares under 2013 Plan to non-employee During the year ended December 31, 2020, 27,125 shares that were granted to non-employee Restricted share grant activity for the year ended December 31, 2020, and the six months ended June 30, 2021, was as follows: Number of non-vested Weighted Weighted Balance as of January 1, 2020 329,156 $ 11.68 1.38 years Granted 79,172 7.90 Vested (89,888 ) 12.25 Forfeited (12,198 ) 11.54 Balance as of December 31, 2020 306,242 $ 10.54 0.93 years Granted 85,098 10.26 Vested (122,322 ) 11.01 Forfeited (7,595 ) 7.90 Balance as of June 30, 2021 261,423 $ 10.30 0.98 years Using the straight-line method of expensing the restricted stock grants, the weighted average estimated value of the shares calculated at the date of grant is recognized as compensation cost in the unaudited condensed consolidated statement of operations over the period to the vesting date. During the six months ended June 30, 2021, the Company recognized $610,849 in share-based Share options issued under the 2013 Plan are not exercisable until the third tenth The movements in the existing share options during the year ended December 31, 2020, and the six months ended June 30, 2021, was as follows: Options Number of Weighted Aggregate Balance as of January 1, 2020 349,936 $ 21.39 — Forfeited during the year (10,000 ) 20.82 — Balance as of December 31, 2020 339,936 21.40 $ — Forfeited during the period (4,500 ) — — Balance as of June 30, 2021 335,436 $ 21.40 $ — There were 335,436 share options that had vested and were exercisable at June 30, 2021 (December 31, 2020: 339,936). The weighted average exercise price of the share options exercisable at June 30, 2021 and December 31, 2020, was $21.40. The weighted-average remaining contractual term of options outstanding and exercisable at June 30, 2021 was 3.18 years (December 31, 2020: 3.67 years). During the six months ended June 30, 2021, the Company recognized a credit of $34,926 in share-based compensation costs relating to options granted under the 2013 Plan (six months ended June 30, 2020: a credit of $77,364 to share-based compensation costs).

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. Commitments and Contingencies The contractual obligations schedule set forth below summarizes our contractual obligations excluding interest payable as of June 30, 2021. Remainder 2022 2023 2024 2025 Thereafter Total (in thousands) Secured term loan facilities and revolving credit facilities 33,832 124,479 202,353 182,527 65,274 — 608,465 2020 Bonds — — — — 100,000 — 100,000 2018 Bonds — — 71,697 — — — 71,697 Navigator Aurora Facility — — — — — 58,018 58,018 Office operating leases 1 791 253 — — — — 1,044 Total contractual obligations $ 34,623 $ 124,732 $ 274,050 $ 182,527 $ 165,274 $ 58,018 $ 839,224 1 The Company occupies office space in London with a lease that commenced in January 2017 for a period of 10 years with a mutual break option in January 2022. The break option was exercised by the Company on April 22, 2021. Please read Note 14—Operating Lease Liabilities for additional information. The Company entered into a three-year lease for office space in New York that terminates on May 31, 2022. The annual gross rent under this lease is approximately $0.4 million, subject to certain adjustments. The lease term for our representative office in Gdynia, Poland is for a period of five years commencing from January 2017. The gross rent per year is approximately $60,000. The weighted average remaining contractual lease term for the above three office leases on June 30, 2021, was 0.68 years.

Operating Lease Liabilities

Operating Lease Liabilities	6 Months Ended
	Jun. 30, 2021
Operating Lease Liabilities [Abstract]
Operating Lease Liabilities	14. Operating Lease Liabilities The Company’s unaudited condensed consolidated balance sheets include a right-of-use The liabilities described below are for the Company’s offices in London, Gdynia and New York which are denominated in various currencies. At June 30, 2021, the weighted average discount rate across the three leases was 3.98%. At June 30, 2021, based on the remaining lease liabilities, the weighted average remaining operating lease term was 0.68 years (December 31, 2020: 5.6 years). The movement in the weighted average remaining lease term from December 31, 2020 arises from the exercise of the break option on the London office lease on April 22, 2021. Under ASC 842, which the Company adopted on January 1, 2019, the ROU asset is a nonmonetary asset and is remeasured into the Company’s reporting currency of the U.S. Dollar using the exchange rate for the applicable currency as at the adoption date of ASC 842. The operating lease liability is a monetary liability and is remeasured quarterly using the current exchange rates, with changes recognized in a manner consistent with other foreign-currency-denominated liabilities in general and administrative expenses in the unaudited condensed consolidated statements of comprehensive income. The break option for the Company’s lease of office space in London which commenced in January 2017 was exercised by the Company on April 22, 2021. The term of the London lease following the exercise of the break option has been reduced to 5 years commencing January 2017, from the 10 year term considered reasonably certain by the Company at the date of adoption of ASC 842. The exercise of the break option is considered a triggering event within the lessee’s control and is a remeasurement event, as defined by paragraph ASC 842-20-35-5. A maturity analysis of the annual undiscounted cash flows of the Company’s operating lease liabilities as at December 31, 2020 and June 30, 2021, is presented in the following table: December 31, 2020 June 30, 2021 (in thousands) One year $ 1,572 $ 1,044 Two years 1,300 — Three years 1,144 — Four years 1,144 — Five years 1,144 — Six years and thereafter 1,222 — Total undiscounted operating lease commitments $ 7,526 $ 1,044 Less: Discount adjustment (1,018 ) (36 ) Total operating lease liabilities 6,508 1,008 Less: current portion (1,276 ) (1,008 ) Operating lease liabilities, non-current $ 5,232 $ —

Cash, Cash Equivalents and Rest

Cash, Cash Equivalents and Restricted Cash	6 Months Ended
	Jun. 30, 2021
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash, Cash Equivalents and Restricted Cash	15. Cash, Cash Equivalents and Restricted Cash The following table shows the breakdown of cash, cash equivalents and restricted cash as of December 31, 2020, and June 30, 2021: December 31, June 30, (in thousands) Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents $ 59,056 $ 96,252 Cash and Cash equivalents held by the lessor VIE 215 104 Restricted cash — — Total cash, cash equivalents and restricted cash $ 59,271 $ 96,356 Included within total cash, cash equivalents and restricted cash as of June 30, 2021, is an amount of $0.1 million (December 31, 2020: $0.2 million) relating to the cash belonging to the lessor VIE that we are required to consolidate under U.S. GAAP. Please read Note 16—Variable Interest Entities for additional information.

Variable Interest Entities

Variable Interest Entities	6 Months Ended
	Jun. 30, 2021
Variable Interest Entities Disclosure [Abstract]
Variable Interest Entities	16. Variable Interest Entities As of June 30, 2021, and December 31, 2020, the Company has consolidated 100% of PT Navigator Khatulistiwa, a VIE (Variable Interest Entity) for which the Company is deemed to be the primary beneficiary, i.e. it has a controlling financial interest in this entity. The Company owns 49% of the VIE’s common stock, all of its secured debt and has voting control. All economic interests in the residual net assets reside with the Company. A VIE is an entity that in general does not have equity investors with voting rights or that has equity investors that do not provide sufficient financial resources for the entity to support its activities. A controlling financial interest in a VIE is present when a company has the power to direct the activities of a VIE that most significantly impact the entity’s economic performance and has the right to residual gains or the obligation to absorb losses that could potentially be significant to the VIE. By virtue of the accounting principle of consolidation, transactions between PT Navigator Khatulistiwa and the Company are eliminated on consolidation. The VIE, PT Navigator Khatulistiwa, as of June 30, 2021, had total assets of $135.4 million (December 31, 2020: $125.9 million) and liabilities of $16.9 million (December 31, 2020: $9.5 million) respectively. These amounts have been included in the Company’s unaudited condensed consolidated balance sheets as of June 30, 2021, and December 31, 2020. In October 2019, the Company entered a sale and leaseback to refinance one of its vessels, Navigator Aurora 2014-09, Following the sale and leaseback refinancing transaction, Navigator Aurora Navigator Aurora 810-10-15-17 Navigator Aurora Navigator Aurora The Company must evaluate whether we are the primary beneficiary of a VIE after concluding that the SPV is in the scope of the variable interest model, we have a variable interest in the entity and the SPV is a VIE. As outlined in ASC 810-10-25-38 day-to-day While we do not hold any equity investments in this lessor VIE, we have concluded that we are the primary beneficiary of the lessor VIE under U.S. GAAP and accordingly we are required to consolidate this lessor VIE into our financial results. Accordingly, although consolidated into our results, we have no control over the funding arrangements negotiated by this lessor VIE entity such as interest rates, maturity and repayment profiles. In consolidating the lessor VIE into our financial results, we must make assumptions regarding the debt amortization profile and the interest rate to be applied against the lessor VIE’s debt principal. Furthermore, our estimation process is dependent upon the timeliness of receipt and accuracy of financial information provided by the lessor VIE entity. By virtue of the accounting principle of consolidation, transactions between consolidated entities are eliminated and accordingly the sale and leaseback refinancing transaction with OCY Aurora is not shown as a liability in the Company’s unaudited condensed consolidated balance sheets, being superseded by the Navigator Aurora Facility between OCY Aurora and Ocean Yield Malta Limited. Please read Note 17—Related Party Transactions for additional information. Under the sale and leaseback transaction we are committed to monthly principal payments until the year five purchase option which include interest payable at a rate of U.S. LIBOR plus 430 basis points per annum. The lessor VIE had total assets and liabilities as of June 30, 2021 of $91.0 million and $58.4 million, respectively (December 31, 2020: $63.5 million and $61.7 million respectively) which have been included in the Company’s unaudited condensed consolidated balance sheets. The liabilities primarily consist of a seven year unsecured loan facility provided by OCY Malta Limited, the parent of OCY Aurora Ltd., The loan facility is subordinated to a further bank loan where OCY Aurora Ltd. is the guarantor and Navigator Aurora The primary assets and liabilities of the lessor VIE that most significantly impact the Company’s unaudited condensed consolidated balance sheets and the financial statement line items in which they are presented as of December 31, 2020 and June 30, 2021, are as follows: December 31, June 30, (in thousands) Assets Cash, cash equivalents and restricted cash $ 215 $ 104 Liabilities Amounts due to related parties, current $ (229 ) $ (206 ) Amounts due to related parties, non-current (61,361 ) (58,018 ) Total liabilities $ (61,590 ) $ (58,224 ) The most significant impact of the lessor VIE’s operations on the Company’s unaudited condensed consolidated statements of operations is interest expense of $0.3 million and $0.6 million for the three and six months ended June 30, 2021 (three and six months ended June 30, 2020: $0.5 million and $1.1 million respectively). The primary impact of the lessor VIE’s cash flows on the Company’s unaudited condensed consolidated statements of cash flows is net cash used in financing activities of $3.3 million arising from a repayment of the Navigator Aurora Facility for the six months ended June 30, 2021 (six months ended June 30, 2020: $3.7 million).

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	17. Related Party Transactions The following table summarizes our transactions with related parties for the three and six months ended June 30, 2020 and 2021: Three months ended June 30, Six months ended June 30, 2020 2021 2020 2021 (in thousands) Net income / (expenses) Luna Pool Agency Limited $ 7,045 $ — $ 7,045 $ — Ocean Yield Malta Limited (491 ) (308 ) (1,122 ) (623 ) Total $ (6,554 ) (308 ) $ 5,923 (623 ) The following table sets out the balances with related parties as at December 31, 2020, and June 30, 2021: December 31, June 30, (in thousands) Receivables / (payables) Luna Pool Agency Limited $ 11,853 $ 5,923 Ocean Yield Malta Limited (61,448 ) (58,087 ) In March 2020, the Company collaborated with Pacific Gas Pte. Ltd. and Greater Bay Gas Co. Ltd. to form and manage the Luna Pool. As part of the formation of the Luna Pool, a new entity, Luna Pool Agency Limited, (“Pool Agency”) was established in May 2020. The investment in the Pool Agency created a 50/50 joint venture with Greater Bay Gas Co. Ltd. The Company’s investment in the Pool Agency is accounted for as an equity investment. Please read Note 5— Investment in Equity Accounted Joint Ventures for additional information. Pool revenues and expenses within the Luna Pool are accounted for in accordance with ASC 808 – Collaborative Arrangements, when two (or more) parties are active participants in the arrangement and exposed to significant risk and rewards dependent on the commercial success of the activity. For a description of our accounting policy in relation to the Luna Pool collaborative arrangement , please read Note 2(a)— Basis of Presentation to the 2020 Annual Report. Transactions with the Luna Pool collaborative arrangement We have presented our share of net income earned under the Luna Pool collaborative arrangement across a number of lines in our unaudited condensed consolidated statements of operations. For revenues and expenses incurred specifically by the Company’s vessels and for which we are deemed to be the principal, these are presented gross on the face of our unaudited condensed consolidated statements of operations within operating revenues, voyage expenses and brokerage commissions. Our share of pool net revenues generated by the other Pool Participant’s vessels in the Luna Pool collaborative arrangement is presented on the face of our unaudited condensed consolidated statements of operations within operating revenues – Luna Pool collaborative arrangement. The other Pool Participant’s share of pool net revenues generated by our vessels in the pool is presented on the face of our unaudited condensed consolidated statements of operations within voyage expenses – Luna Pool collaborative arrangement. The portion of the Commercial Manager’s fee which is due from the other Pool Participant is presented on the face of our unaudited condensed consolidated statements of operations as other income. The following table summarizes our net income generated from our participation in the Luna Pool collaborative arrangement for the three and six months ended June 30, 2020 and 2021: Three months ended Six months ended June 30, June 30, June 30, June 30, (in thousands) Income / (expenses) Time and Voyage charter revenues $ 10,246 $ 24,909 $ 10,246 $ 43,790 Time and Voyage charter revenues from Luna Pool collaborative arrangement 2,596 5,546 2,596 10,785 Brokerage commissions (170 ) (432 ) (170 ) (708 ) Voyage expenses (2,701 ) (9,233 ) (2,701 ) (16,732 ) Voyage expenses – Luna Pool collaborative arrangement (3,043 ) (5,663 ) (3,043 ) (9,796 ) Total net operating income from the Luna Pool 6,928 15,127 6,928 27,339 Other income 117 88 117 160 Total net income from the Luna Pool $ 7,045 $ 15,215 $ 7,045 $ 27,499 Transactions with the Luna Pool Agency Limited The Company’s related party balances with the Pool Agency consisted of the following at December 31, 2020 and June 30, 2021: December 31, June 30, (in thousands) (in thousands) Receivables / (payables) Other assets $ 11,853 $ 5,923 Total assets $ 11,853 $ 5,923 The net balance as of June 30, 2021 and December 31, 2020 is presented as amounts due from related parties on our unaudited condensed consolidated balance sheets and arises from amounts owed by the Pool Agency to the Company relating to working capital, pool distributions and voyage expenses for the Company’s vessels within the Luna Pool, offset by amounts received by the Company relating to hire and freight of the Company’s vessels within the Luna Pool . Transactions with Ocean Yield Malta Limited In October 2019, the Company sold Navigator Aurora In October 2019, OCY Aurora Ltd., which owns Navigator Aurora The Navigator Aurora Facility is a seven-year unsecured loan provided by OCY Malta Limited, the parent of OCY Aurora Ltd. and a wholly owned subsidiary of Ocean Yield ASA. The Navigator Aurora Facility is subordinated to a further bank loan where OCY Aurora Ltd. is the guarantor and Navigator Aurora Navigator Aurora The Navigator Aurora Facility bears interest at three-month non-current non-contractual The following table sets out the Company’s related party transactions with Ocean Yield Malta Limited for the three and six months ended June 30, 2020 and 2021: Three months ended Six months ended June 30, June 30, June 30, June 30, (in thousands) Income / (expenses) General and Administrative expenses $ (7) $ — $ (9) $ (4) Interest Expense (482 ) (304 ) (1,113 ) (619 ) Total $ (489 ) $ (304 ) $ (1,122 ) $ (623 ) The following table sets out the Company’s related party balances with Ocean Yield Malta Limited as at December 31, 2020 and June 30, 2021: December 31, June 30, (in thousands) Receivables / (payables) Accrued interest and trade payables $ (229 ) $ (206 ) Navigator Aurora Facility, net of deferred financing costs (61,216 ) (57,878 ) Other non-current (3 ) (3 ) Total liabilities $ (61,448 ) $ (58,087 )

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	18. Subsequent Events On August 4, 2021, the Company entered into the previously announced transaction with Naviera Ultranav Limitada (“Ultranav”) to combine the Ultragas ApS (“Ultragas”) fleet and business activities with Navigator, by acquiring two entities, Othello Shipping Company S.A. with its 18 wholly owned vessels owning entities and Ultragas ApS, (the vessels’ operator) with its subsidiary (Ultraship, the in-house • seven modern 22,000cbm handysize semi-refrigerated vessels; • five 12,000cbm ethylene vessels and; • six gas carriers in the 3,770 -9,000 cbm The acquisition price for the entities comprised of approximately 21.2 million new shares of the Company’s common stock issued to Ultranav as well as the Company assuming the acquired entities approximately $192.7 million of debt and $17.5 million of cash. The price of the Company’s common stock on the date of acquisition was $9.57. The debt consists of five bank loans, secured on a total of 13 of the 18 vessels acquired, the other five vessels are unencumbered. The bank loans, which in aggregate have half yearly repayments of approximately $13.6 million, mature from June 2026 and attract interest at U.S. Libor plus a margin of between 1.9% and 2.65%. In each case interest is fixed by an interest rate swap of approximately 2.0%. The financial covenants on these five bank loans were modified to be consistent with those of Navigator. The transaction was finalized after the balance sheet date and there are no adjustments recognized within the unaudited condensed consolidated financial statements for the six months ended June 30, 2021, or the balance sheet as of June 30, 2021. At the date of issue of these unaudited condensed consolidated financial statements, due to the short period of time that has elapsed since the transaction was finalized, the initial accounting for the business combination is incomplete, as well as a local GAAP conversion to U.S. GAAP. As a result, the Company is not able to determine for disclosure, as directed by paragraph 805-10-50-2 pro-forma On September 28, 2021, the Company agreed to sell one of the older acquired vessels, the Happy Bride, a 1999 built 6,400 cbm LPG carrier to a third party for $4.75 million. The sale completed on October 12, 2021. On October 7, 2021, the Company entered into a lease for office space in London that commences in January 2022, at the expiry of the existing lease. The lease is for a period of ten years with a mutual break option in January 2027, the fifth anniversary from the commencement of the lease. The annual lease cost is approximately $1.1 million, but is reduced by a total rent free period of 27 months over the ten years period of the lease. If the lease is terminated on the break option date the total commitment payable would be $4.3 million, or $8.6 million if the lease continues for the full tenor of 10 years.

Basis of Presentation (Policies

Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying Navigator Holdings Ltd. (the “Company”), unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary for a fair presentation of the financial position of the Company and its subsidiaries as of June 30, 2021; the results of operations for the three and six months ended June 30, 2020 and 2021, the statement of stockholders’ equity for the three and six months ended June 30, 2020 and 2021, and cash flows for the six months ended June 30, 2020 and 2021. Unless the context otherwise requires, all references in the unaudited condensed consolidated financial statements to “our,” “we,” and “us” refer to the Company. The unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The accompanying unaudited condensed consolidated financial statements include the accounts of the Company, its subsidiaries and Variable Interest Entities (“VIE”) for which the Company is a primary beneficiary and are also consolidated (please read Note 16—Variable Interest Entities for additional information). All intercompany accounts and transactions have been eliminated in consolidation. A discussion of the Company’s significant accounting policies can be found in the Company’s consolidated financial statements included in the 2020 Annual Report. There have been no material changes to these policies in the six months ended June 30, 2021, apart from the below: On December 18, 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2019-12, In January 2020, the FASB issued ASU 2020-01, 2020-01 These unaudited condensed consolidated financial statements of the Company and its subsidiaries have been prepared in accordance with U.S. GAAP for interim reporting. As such, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. It is recommended that these financial statements be read in conjunction with our audited consolidated financial statements and notes thereto for the year ended December 31, 2020, included in the 2020 Annual Report. The results for the three and six months ended June 30, 2021, are not necessarily indicative of results for the year ended December 31, 2021 or any other future periods.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In March 2020, the FASB issued ASU 2020-04, 2020-04 In August 2020, the FASB issued ASU 2020-06, 470-20) 815-40)”,

Revenue Recognition (Policies)

Revenue Recognition (Policies)	6 Months Ended
	Jun. 30, 2021
Revenue Recognition [Abstract]
Revenue Recognition	2. Revenue Recognition The Company receives its revenue streams from three different sources; vessels on time charters (which are accounted for as leases under Topic 842); voyage charters; and contracts of affreightment (“COA”) accounted for under Topic 606. Revenues from the Luna Pool collaborative arrangement are accounted for under ASC 808. Time charter revenue is payable monthly in advance whilst revenue from voyage charters and COAs is due upon discharge of the cargo at the discharge port. In the case of voyage charters, the vessel is contracted for a voyage, or a series of voyages, between two or more ports and the Company is paid for the cargo transported. Revenue from COAs is recognized on the same basis as revenue from voyage charters, as they are essentially a series of consecutive voyage charters. Payment from voyage charters and COAs is due upon discharge of the cargo at the discharge port. Since January 1, 2018, following adoption of ASU No. 2014-09, Under this revenue recognition standard, the Company has identified certain costs incurred to fulfill a contract with a charterer, which are costs incurred following the commencement of a contract or charter party but before the loading of the cargo commences. These directly related costs are generally fuel or any canal or port costs incurred to get the vessel from its position at inception of the contract to the load port to commence loading of the cargo. These costs are deferred and amortized over the duration of the performance obligation on a time basis. Voyage charters and COAs have an expected duration of one year or less. The Company has applied optional exemptions on adoption of the revenue standard, as set out in Topic 606-10-50-14 In addition, accrued income relates to our conditional right to consideration for our completed performance under contracts and is recognized according to our performance. Contract liabilities or deferred income includes payments received in advance of performance under contracts and is recognized when performance under the respective contract has been completed. For vessels contracted under time charters, the arrangements are for a specified period of time. The Company receives a fixed charter rate per on-hire add-on Operating revenues The following table compares our operating revenues by the source of revenue stream for the three and six months ended June 30, 2020 and 2021: Three months ended June 30, (in thousands) Six months ended June 30, (in thousands) 2020 2021 2020 2021 Operating revenues: Time charters $ 43,146 $ 41,903 $ 93,841 $ 84,582 Time charters from Luna Pool collaborative arrangement — 930 — 1,279 Voyage charters 36,723 38,250 67,285 76,079 Voyage charters from Luna Pool collaborative arrangement 2,596 4,616 2,596 9,507 Total operating revenues $ 82,465 $ 85,699 $ 163,722 $ 171,447 Voyage Charter revenues Voyage charter revenues, which include revenues from contracts of affreightment, are shown net of address commissions. As of June 30, 2021, for voyage charters and contracts of affreightment, services accounted for under Topic 606, the amount of contract assets reflected within accrued income on the Company’s unaudited condensed consolidated balance sheets was $3.0 million (December 31, 2020: $11.4 million). Changes in the contract asset balance at the balance sheet dates reflect income accrued after loading of the cargo commences but before an invoice has been raised to the charterer, as well as changes in the number of the Company’s vessels contracted under voyage charters or contracts of affreightment. The amount of contract liabilities reflected within deferred income on the Company’s unaudited condensed consolidated balance sheets was $1.4 million as of June 30, 2021 (December 31, 2020: $1.6 million). The opening and closing balance of receivables from voyage charters, including contracts of affreightment, was $3.3 million and $8.3 million, respectively, as of June 30, 2021 (December 31, 2020: $4.2 million and $3.3 million, respectively) and is reflected within net accounts receivable on the Company’s unaudited condensed consolidated balance sheets. The amount allocated to costs incurred to fulfill a contract with a charterer, which are costs incurred following the commencement of a contract or charter party but before the loading of the cargo commences, was $1.0 million as of June 30, 2021 (December 31, 2020: $1.5 million) and is reflected within prepaid expenses and other current assets on the Company’s unaudited condensed consolidated balance sheets. Time charter revenues: As of June 30, 2021, 20 of the Company’s 38 vessels were subject to time charters, fifteen of which will expire within one year, three of which will expire within three years and two which will expire after more than five years from the balance sheet date. (December 31, 2020: 19 of the Company’s 38 vessels, were subject to time charters, eleven of which will expire within one year, six which will expire within three years, and two which will expire after more than five years from the balance sheet date). The estimated undiscounted cash flows for committed time charter revenues expected to be received on an annual basis for ongoing time charters, as of each June 30, is as follows: (in thousands) Within 1 year: $ 143,372 2 years: $ 53,346 3 years: $ 32,649 4 years: $ 21,480 5 years: $ 21,480 More than 5 years: $ 16,152 For time charter revenues accounted for under Topic 842, the amount of accrued income on the Company’s unaudited condensed consolidated balance sheets as of June 30, 2021 was $3.6 million (December 31, 2020: $8.4 million). The amount of hire payments received in advance under time charter contracts, recognized as a liability and reflected within deferred income on the Company’s unaudited condensed consolidated balance sheets as of June 30, 2021, was $12.5 million (December 31, 2020: $10.0 million). Deferred income allocated to time charters will be recognized ratably over time, which is expected to be within one month from June 30, 2021. Revenues from Luna Pool collaborative arrangement Revenues from the Luna Pool collaborative arrangement for the three and six months ended June 30, 2021, which are accounted for under ASC 808 – Collaborative Arrangements, represent our share of pool net revenues generated by the other Pool Participant’s vessels in the Luna Pool. These include revenues from voyage charters and contract of affreightment, which are accounted for under Topic 606, in addition to revenues from time charters, which are accounted for under Topic 842. Please read Note 5— Investment in Equity Accounted Joint Ventures for additional information. The Pool Participants manage and participate in the activities of the Luna Pool through an executive committee comprising equal membership from both Pool Participants. Certain decisions made by the executive committee as to the operations of the Luna Pool require the unanimous agreement of both participants with others requiring a majority of votes. At this time we control 66% of the votes. The Company’s wholly owned subsidiary, NGT Services (UK) Limited acts as commercial manager (“Commercial Manager”) to the Luna Pool. Under the pool agreement, the Commercial Manager is responsible, as agent, for the marketing and chartering of the participating vessels, collection of revenues and paying voyage costs such as port call expenses, bunkers and brokers’ commissions in relation to charter contracts, but the vessel owners continue to be fully responsible for the financing, insurance, crewing and technical management of their respective vessels. The Commercial Manager receives a fee based on the net revenues of the Luna Pool, which is levied on the Pool Participants. The portion of the Commercial Manager’s fee which is due from the other Pool Participant was a net amount of $0.1 million and $0.2 million, after the elimination of inter group income, for the three and six months ended June 30, 2021 respectively, and is presented as other income within our unaudited condensed consolidated statements of operations. The Luna Pool became operational during the second quarter of 2020 and consequently the other income for both the three and six months ended June 30, 2020 was $0.1 million. Pool revenues and expenses within the Luna Pool are accounted for in accordance with ASC 808 – Collaborative Arrangements, when two (or more) parties are active participants in the arrangement and exposed to significant risk and rewards dependent on the commercial success of the activity. Pool earnings (gross earnings of the pool less costs and overheads of the Luna Pool and fees to the Commercial Manager) are aggregated and then allocated to the Pool Participants in accordance with an apportionment for each participant’s vessels multiplied by the number of days each of their vessels are on hire in the pool during the relevant period and therefore the Company is exposed to risk and rewards dependent on the commercial success of the Luna Pool. We have concluded that the Company is an active participant due to its representation on the executive committee and the participation of the Commercial Manager, as is the other Pool Participant. We have presented our share of net income earned under the Luna Pool collaborative arrangement across a number of lines in our unaudited condensed consolidated statements of operations. Our share of pool net revenues generated by the other Pool Participant’s vessels in the Luna Pool collaborative arrangement amounted to $5.6 million and $10.8 million for the three and six months ended June 30, 2021, respectively, and is presented on the face of our unaudited condensed consolidated statements of operations within operating revenues – Luna Pool collaborative arrangement. The other Pool Participant’s share of pool net revenues generated by our vessels in the pool amounted to $5.7 million and $9.8 million for the three and six months ended June 30, 2021, respectively, and is presented on the face of our unaudited condensed consolidated statements of operations within voyage expenses – Luna Pool collaborative arrangement. The Luna Pool became operational during the quarter ended June 30, 2020 and consequently the impact on the Company’s consolidated statements of operations for both the three and six months ended June 30, 2020 was operating revenues from Luna Pool collaborative arrangement of $2.6 million, and voyage expenses from Luna Pool collaborative arrangement of $3.0 million.

Revenue Recognition (Tables)

Revenue Recognition (Tables)	6 Months Ended
	Jun. 30, 2021
Revenue Recognition [Abstract]
Summary of Operating Revenue by Source of Revenue Stream	The following table compares our operating revenues by the source of revenue stream for the three and six months ended June 30, 2020 and 2021: Three months ended June 30, (in thousands) Six months ended June 30, (in thousands) 2020 2021 2020 2021 Operating revenues: Time charters $ 43,146 $ 41,903 $ 93,841 $ 84,582 Time charters from Luna Pool collaborative arrangement — 930 — 1,279 Voyage charters 36,723 38,250 67,285 76,079 Voyage charters from Luna Pool collaborative arrangement 2,596 4,616 2,596 9,507 Total operating revenues $ 82,465 $ 85,699 $ 163,722 $ 171,447
Summary of Committed Time Charter Income for Future Periods	The estimated undiscounted cash flows for committed time charter revenues expected to be received on an annual basis for ongoing time charters, as of each June 30, is as follows: (in thousands) Within 1 year: $ 143,372 2 years: $ 53,346 3 years: $ 32,649 4 years: $ 21,480 5 years: $ 21,480 More than 5 years: $ 16,152

Current Expected Credit Losses

Current Expected Credit Losses (Tables)	6 Months Ended
	Jun. 30, 2021
Credit Loss [Abstract]
Schedule of Allowance for Credit Losses	(in thousands) Balance as at December 31, 2019 $ — Allowance recognized on transition 151 Provision for expected credit losses during 2020 10 Balance as at December 31, 2020 $ 161 Current period provision for expected credit losses 136 Balance as at June 30, 2021 $ 297

Vessels, net (Tables)

Vessels, net (Tables)	6 Months Ended
	Jun. 30, 2021
Vessels	Vessel Drydocking Total (in thousands) Cost December 31, 2020 $ 2,062,513 $ 39,654 $ 2,102,167 Additions 323 10,061 10,384 Impairment following vessel damage (17,000 ) — (17,000 ) Write-offs of fully amortized assets — (6,576 ) (6,576 ) June 30, 2021 $ 2,045,836 $ 43,139 $ 2,088,975 Accumulated Depreciation December 31, 2020 $ 536,436 $ 20,043 $ 556,479 Charge for the period 34,018 4,516 38,534 Impairment following vessel damage (11,600 ) — (11,600 ) Write-offs of fully amortized assets — (6,576 ) (6,576 ) June 30, 2021 $ 558,854 $ 17,983 $ 576,837 Net Book Value December 31, 2020 $ 1,526,077 $ 19,611 $ 1,545,688 June 30, 2021 $ 1,486,982 $ 25,156 $ 1,512,138

Investment in Equity Accounte_2

Investment in Equity Accounted Joint Venture (Tables)	6 Months Ended
	Jun. 30, 2021
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Participation in Investments That Are Accounted For Using The Equity Method	As at December 31, 2020 and June 30, 2021, we had the following participation in investments that are accounted for using the equity method: December 31, June 30, Enterprise Navigator Ethylene Terminal L.L.C. (“Export Terminal Joint Venture”) 50 % 50 % Luna Pool Agency Limited. (“Pool Agency”) 50 % 50 %
Schedule of Investments in Equity Accounted Joint Venture	The table below represents the Company’s investment into the Export Terminal Joint Venture, pursuant to which the Company has a 50% economic interest in building and operating the Marine Export Terminal, as of December 31, 2020 and June 30, 2021: 2020 2021 (in thousands) Investment in equity accounted joint venture at January 1 $ 130,660 $ 148,665 Equity contributions to joint venture entity 17,000 4,000 Share of results 651 1,396 Distributions received from joint venture entity — (6,850 ) Capitalized interest and deferred financing costs 354 — Total investment in equity accounted joint venture at December 31 and June 30 $ 148,665 $ 147,211

Secured Term Loan Facilities _2

Secured Term Loan Facilities and Revolving Credit Facilities (Tables)	6 Months Ended
	Jun. 30, 2021
Schedule of Breakdown of Secured Term Loan Facilities and Total Deferred Financing Costs Split Between Current and Non-Current Liabilities	The following table shows the breakdown of all secured term loan facilities and total deferred financing costs split between current and non-current December 31, June 30, (in thousands) Current Liability Current portion of secured term loan facilities $ 67,936 $ 89,056 Less: current portion of deferred financing costs (2,274 ) (2,341 ) Current portion of secured term loan facilities, net of deferred financing costs $ 65,662 $ 86,715 Non-Current Secured term loan facilities and revolving credit facilities net of current portion* $ 617,994 $ 577,427 Less: non-current (4,183 ) (3,553 ) Non-current non-current $ 613,811 $ 573,874 * Includes amounts relating to the Navigator Aurora Facility held within a lessor entity (for which legal ownership resides with a financial institution) that we are required to consolidate under U.S. GAAP into our financial statements as a variable interest entity.
Senior Secured Bonds [Member]
Schedule of Breakdown of Secured Term Loan Facilities and Total Deferred Financing Costs Split Between Current and Non-Current Liabilities	The following table shows the breakdown of our senior secured bond and total deferred financing costs as of December 31, 2020 and June 30, 2021: December 31, June 30, (in thousands) Senior Secured Bond Total Bond $ 70,299 $ 69,961 Less deferred financing costs (719 ) (593 ) Total Bond, net of deferred financing costs $ 69,580 $ 69,368
2020 Senior Unsecured Bonds [Member]
Schedule of Breakdown of Secured Term Loan Facilities and Total Deferred Financing Costs Split Between Current and Non-Current Liabilities	The following table shows the breakdown of our senior unsecured bond and total deferred financing costs as of December 31, 2020 and June 30, 2021: December 31, June 30, 2021 (in thousands) Senior Unsecured Bond Total Bond $ 100,000 $ 100,000 Less deferred financing costs (1,842 ) (1,645 ) Total Bond, net of deferred financing costs $ 98,158 $ 98,355

Derivative Instruments Accoun_2

Derivative Instruments Accounted for at Fair Value (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Estimated Fair Value and Carrying Value of Assets and Liabilities Measured at Fair Value on Recurring Basis, Non-recurring Basis	The following table includes the estimated fair value of those assets and liabilities that are measured at fair value on a recurring basis and are carried at fair value as at December 31, 2020 and June 30, 2021: December 31, 2020 June 30, 2021 Fair Value Hierarchy Level Fair Fair Fair (in thousands) Cross-currency interest rate swap agreement Level 2 (2,896 ) (2,943 ) Interest rate swap agreements Level 2 (111 ) 215

Fair Value of Financial Instr_2

Fair Value of Financial Instruments Not Accounted For at Fair Value (Tables)	6 Months Ended
	Jun. 30, 2021
Investments, All Other Investments [Abstract]
Schedule of Estimated Fair Value and Carrying Value of Assets and Liabilities Measured at Fair Value on Recurring Basis, Non-recurring Basis	The following table includes the estimated fair value and carrying value of those assets and liabilities where the fair value does not approximate to carrying value. The table excludes cash, cash equivalents, restricted cash, accounts receivable, accounts payable, secured term loan facilities and revolving credit facilities, accrued expenses and other liabilities because the fair value approximates carrying value and, for accounts receivable and payable, are due in one year or less. December 31, 2020 June 30, 2021 Financial Asset/Liability Fair Carrying Fair Value Carrying Fair Value (in thousands) 2018 Bonds (note 7) Level 2 (70,299 ) (72,672 ) (69,691 ) (72,759 ) 2020 Bonds (note 8) Level 2 (100,000 ) (103,500 ) (100,000 ) (105,000 )

Earnings per Share (Tables)

Earnings per Share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Calculation of Basic and Diluted Number of Weighted Average Outstanding Shares	Three months ended Six months ended 2020 2021 2020 2021 Basic and diluted income / (loss) available to common stockholders (in thousands) $ 3,008 $ 260 $ (5,154 ) $ 3,080 Basic weighted average number of shares: 55,905,600 55,971,121 55,871,893 55,935,859 Effect of dilutive potential share options*: 348,178 335,436 — 337,674 Diluted weighted average number of shares 56,253,778 56,306,557 55,871,893 56,273,533 * Due to a loss for the six months ended June 30, 2020, no incremental shares are included because the effect would be antidilutive. The number of potential dilutive shares excluded from the calculation for the six months ended June 30, 2020 is 349,057.

Share-Based Compensation (Table

Share-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Restricted Share Grant Activity	Restricted share grant activity for the year ended December 31, 2020, and the six months ended June 30, 2021, was as follows: Number of non-vested Weighted Weighted Balance as of January 1, 2020 329,156 $ 11.68 1.38 years Granted 79,172 7.90 Vested (89,888 ) 12.25 Forfeited (12,198 ) 11.54 Balance as of December 31, 2020 306,242 $ 10.54 0.93 years Granted 85,098 10.26 Vested (122,322 ) 11.01 Forfeited (7,595 ) 7.90 Balance as of June 30, 2021 261,423 $ 10.30 0.98 years
Summary of Stock Option Activity	The movements in the existing share options during the year ended December 31, 2020, and the six months ended June 30, 2021, was as follows: Options Number of Weighted Aggregate Balance as of January 1, 2020 349,936 $ 21.39 — Forfeited during the year (10,000 ) 20.82 — Balance as of December 31, 2020 339,936 21.40 $ — Forfeited during the period (4,500 ) — — Balance as of June 30, 2021 335,436 $ 21.40 $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Summary of Contractual Obligations	The contractual obligations schedule set forth below summarizes our contractual obligations excluding interest payable as of June 30, 2021. Remainder 2022 2023 2024 2025 Thereafter Total (in thousands) Secured term loan facilities and revolving credit facilities 33,832 124,479 202,353 182,527 65,274 — 608,465 2020 Bonds — — — — 100,000 — 100,000 2018 Bonds — — 71,697 — — — 71,697 Navigator Aurora Facility — — — — — 58,018 58,018 Office operating leases 1 791 253 — — — — 1,044 Total contractual obligations $ 34,623 $ 124,732 $ 274,050 $ 182,527 $ 165,274 $ 58,018 $ 839,224 1 The Company occupies office space in London with a lease that commenced in January 2017 for a period of 10 years with a mutual break option in January 2022. The break option was exercised by the Company on April 22, 2021. Please read Note 14—Operating Lease Liabilities for additional information.

Operating Lease Liabilities (Ta

Operating Lease Liabilities (Tables)	6 Months Ended
	Jun. 30, 2021
Operating Lease Liabilities [Abstract]
Maturity Analysis of The Annual Undiscounted Cash Flows of The Company's Operating Lease Liabilities	A maturity analysis of the annual undiscounted cash flows of the Company’s operating lease liabilities as at December 31, 2020 and June 30, 2021, is presented in the following table: December 31, 2020 June 30, 2021 (in thousands) One year $ 1,572 $ 1,044 Two years 1,300 — Three years 1,144 — Four years 1,144 — Five years 1,144 — Six years and thereafter 1,222 — Total undiscounted operating lease commitments $ 7,526 $ 1,044 Less: Discount adjustment (1,018 ) (36 ) Total operating lease liabilities 6,508 1,008 Less: current portion (1,276 ) (1,008 ) Operating lease liabilities, non-current $ 5,232 $ —

Cash, Cash Equivalents and Re_2

Cash, Cash Equivalents and Restricted Cash (Tables)	6 Months Ended
	Jun. 30, 2021
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Schedule of breakdown of cash, cash equivalents and restricted cash	The following table shows the breakdown of cash, cash equivalents and restricted cash as of December 31, 2020, and June 30, 2021: December 31, June 30, (in thousands) Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents $ 59,056 $ 96,252 Cash and Cash equivalents held by the lessor VIE 215 104 Restricted cash — — Total cash, cash equivalents and restricted cash $ 59,271 $ 96,356

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	6 Months Ended
	Jun. 30, 2021
Variable Interest Entities Disclosure [Abstract]
Schedule of Assets and Liabilities of the Lessor VIE	The primary assets and liabilities of the lessor VIE that most significantly impact the Company’s unaudited condensed consolidated balance sheets and the financial statement line items in which they are presented as of December 31, 2020 and June 30, 2021, are as follows: December 31, June 30, (in thousands) Assets Cash, cash equivalents and restricted cash $ 215 $ 104 Liabilities Amounts due to related parties, current $ (229 ) $ (206 ) Amounts due to related parties, non-current (61,361 ) (58,018 ) Total liabilities $ (61,590 ) $ (58,224 )

Related Party Transactions (Tab

Related Party Transactions (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure of Related Party Transactions [Line Items]
Schedule Of Related Party Transactions Income Expenses	The following table summarizes our transactions with related parties for the three and six months ended June 30, 2020 and 2021: Three months ended June 30, Six months ended June 30, 2020 2021 2020 2021 (in thousands) Net income / (expenses) Luna Pool Agency Limited $ 7,045 $ — $ 7,045 $ — Ocean Yield Malta Limited (491 ) (308 ) (1,122 ) (623 ) Total $ (6,554 ) (308 ) $ 5,923 (623 )
Schedule Of Balances Due To And From Related Parties	The following table sets out the balances with related parties as at December 31, 2020, and June 30, 2021: December 31, June 30, (in thousands) Receivables / (payables) Luna Pool Agency Limited $ 11,853 $ 5,923 Ocean Yield Malta Limited (61,448 ) (58,087 )
Luna Pool Agency Limited [Member]
Disclosure of Related Party Transactions [Line Items]
Disclosure Of Operating Results On Account Of Related Party Transactions	The following table summarizes our net income generated from our participation in the Luna Pool collaborative arrangement for the three and six months ended June 30, 2020 and 2021: Three months ended Six months ended June 30, June 30, June 30, June 30, (in thousands) Income / (expenses) Time and Voyage charter revenues $ 10,246 $ 24,909 $ 10,246 $ 43,790 Time and Voyage charter revenues from Luna Pool collaborative arrangement 2,596 5,546 2,596 10,785 Brokerage commissions (170 ) (432 ) (170 ) (708 ) Voyage expenses (2,701 ) (9,233 ) (2,701 ) (16,732 ) Voyage expenses – Luna Pool collaborative arrangement (3,043 ) (5,663 ) (3,043 ) (9,796 ) Total net operating income from the Luna Pool 6,928 15,127 6,928 27,339 Other income 117 88 117 160 Total net income from the Luna Pool $ 7,045 $ 15,215 $ 7,045 $ 27,499
Disclosure Details Of Balance Due From To Related Parties	The Company’s related party balances with the Pool Agency consisted of the following at December 31, 2020 and June 30, 2021: December 31, June 30, (in thousands) (in thousands) Receivables / (payables) Other assets $ 11,853 $ 5,923 Total assets $ 11,853 $ 5,923
Ocean Yield Malta Limited [Member]
Disclosure of Related Party Transactions [Line Items]
Disclosure Of Operating Results On Account Of Related Party Transactions	The following table sets out the Company’s related party transactions with Ocean Yield Malta Limited for the three and six months ended June 30, 2020 and 2021: Three months ended Six months ended June 30, June 30, June 30, June 30, (in thousands) Income / (expenses) General and Administrative expenses $ (7) $ — $ (9) $ (4) Interest Expense (482 ) (304 ) (1,113 ) (619 ) Total $ (489 ) $ (304 ) $ (1,122 ) $ (623 )
Disclosure Details Of Balance Due From To Related Parties	The following table sets out the Company’s related party balances with Ocean Yield Malta Limited as at December 31, 2020 and June 30, 2021: December 31, June 30, (in thousands) Receivables / (payables) Accrued interest and trade payables $ (229 ) $ (206 ) Navigator Aurora Facility, net of deferred financing costs (61,216 ) (57,878 ) Other non-current (3 ) (3 ) Total liabilities $ (61,448 ) $ (58,087 )

Revenue Recognition - Summary o

Revenue Recognition - Summary of Operating Revenue by Source of Revenue Stream (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues	$ 85,699	$ 82,465	$ 171,447	$ 163,722
Luna Pool Agency Limited [Member]
Revenues		2,596
Time Charters [Member]
Revenues	41,903	43,146	84,582	93,841
Time Charters [Member] | Luna Pool Agency Limited [Member]
Revenues	930		1,279
Voyage Charters [Member]
Revenues	38,250	$ 36,723	76,079	67,285
Voyage Charters [Member] | Luna Pool Agency Limited [Member]
Revenues	$ 4,616		$ 9,507	$ 2,596

Revenue Recognition - Summary_2

Revenue Recognition - Summary of Committed Time Charter Income for Future Periods (Details) $ in Thousands	Jun. 30, 2021USD ($)
Not Later Than One Year [Member]
Within 1 year:	$ 143,372
More Than One Year But Not Later Than Two Years [Member]
2 years:	53,346
More Than Two Years But Not Later Than Three Years [Member]
3 years:	32,649
More Than Three Years But Not Later Than Four Years [Member]
4 years:	21,480
More Than Four Years But Not Later Than Five Years [Member]
5 years:	21,480
Later Than Five Years [Member]
More than 5 years:	$ 16,152

Revenue Recognition - Additiona

Revenue Recognition - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Contract Assets	$ 3,000		$ 3,000		$ 11,400
Deferred income	13,981		13,981		11,604
Contract Costs Incurred In Advance	1,000		$ 1,000		1,500
Revenue, performance obligation, description of timing			the Company’s 38 vessels were subject to time charters, fifteen of which will expire within one year, three of which will expire within three years and two which will expire after more than five years from the balance sheet date.
Revenues	85,699	$ 82,465	$ 171,447	$ 163,722
Accounts receivable, net	$ 20,696		$ 20,696		14,451
NGT Services Limited [Member]
Equity method investment, ownership percentage	66.00%		66.00%
Trading Revenue [Member]
Revenues	$ 5,600		$ 10,800
Other Income [Member]
Management fee expense	100	100	200	100
Voyage Expenses Member [Member]
Revenues	5,700	$ 2,600	9,800	$ 3,000
Accounting Standards Update 2014-09 [Member]
Contract Assets	3,600		3,600		8,400
Contracts of Affreightment [Member]
Accounts receivable, net					4,200	$ 3,300
Voyage Charters [Member]
Deferred income	1,400		1,400		1,600
Accounts receivable, net					3,300	$ 8,300
Cargo Commences [Member] | Accounting Standards Update 2014-09 [Member]
Deferred income	$ 12,500		$ 12,500		$ 10,000

Current Expected Credit Losse_2

Current Expected Credit Losses - Schedule of Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Credit Loss [Abstract]
Beginning balance	$ 161
Allowance Recognized on Transition		151
Provision for expected credit losses	136	10
Ending balance	$ 297	$ 161

Current Expected Credit Losse_3

Current Expected Credit Losses - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2020USD ($)
Accounting Standards Update 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowances for credit losses transition provision adjustment to equity	$ 0.1

Vessels, net - Vessels (Detail)

Vessels, net - Vessels (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Net Book Value, ending balance	$ 527	$ 502
Vessels [Member]
Property, Plant and Equipment [Line Items]
Cost, beginning balance	2,102,167
Cost, Additions	10,384
Cost, Impairment following vessel damage	(17,000)
Cost, Write-offs of fully amortized assets	(6,576)
Cost, ending balance	2,088,975
Accumulated Depreciation, beginning balance	556,479
Accumulated Depreciation, Charge for the period	38,534
Accumulated Depreciation, Impairment following vessel damage	(11,600)
Accumulated Depreciation, Write-offs of fully amortized assets	(6,576)
Accumulated Depreciation, ending balance	576,837
Net Book Value, ending balance	1,512,138	1,545,688
Vessels [Member] | Vessel [Member]
Property, Plant and Equipment [Line Items]
Cost, beginning balance	2,062,513
Cost, Additions	323
Cost, Impairment following vessel damage	(17,000)
Cost, ending balance	2,045,836
Accumulated Depreciation, beginning balance	536,436
Accumulated Depreciation, Charge for the period	34,018
Accumulated Depreciation, Impairment following vessel damage	(11,600)
Accumulated Depreciation, ending balance	558,854
Net Book Value, ending balance	1,486,982	1,526,077
Vessels [Member] | Drydocking [Member]
Property, Plant and Equipment [Line Items]
Cost, beginning balance	39,654
Cost, Additions	10,061
Cost, Write-offs of fully amortized assets	(6,576)
Cost, ending balance	43,139
Accumulated Depreciation, beginning balance	20,043
Accumulated Depreciation, Charge for the period	4,516
Accumulated Depreciation, Write-offs of fully amortized assets	(6,576)
Accumulated Depreciation, ending balance	17,983
Net Book Value, ending balance	$ 25,156	$ 19,611

Vessels, net - Additional Infor

Vessels, net - Additional Information (Detail) $ in Thousands	Jun. 10, 2021USD ($)	Jun. 30, 2021USD ($)Vessels	Dec. 31, 2020USD ($)Vessels
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net		$ 527	$ 502
Variable Interest Entities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, cost		83,500	82,900
Property, plant and equipment, net		70,900	71,000
Time Charter Agreements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, cost		1,167,000	1,084,000
Property, plant and equipment, net		$ 895,000	$ 839,000
Number of vessels contracted | Vessels		20	19
Vessels In Operation [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, cost		$ 2,088,975	$ 2,102,167
Property, plant and equipment, net		1,512,138	1,545,688
Vessels [Member] | Vessels In Operation [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, cost		2,045,836	2,062,513
Property, plant and equipment, net		1,486,982	1,526,077
Write down on property plant and equipment	$ 5,400
Property plant and equipment damages not recoverable	$ 100
Collateralized Loan Obligations [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net		$ 1,331,000	$ 1,359,000

Investment in Equity Accounte_3

Investment in Equity Accounted Joint Ventures - Schedule of Participation in Investments That Are Accounted For Using The Equity Method (Detail)	Jun. 30, 2021	Dec. 31, 2020
Enterprise Navigator Ethylene Terminals L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	50.00%	50.00%
Luna Pool Agency Limited [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	50.00%	50.00%

Investment in Equity Accounte_4

Investment in Equity Accounted Joint Venture - Summary of Investment in Equity Accounted Joint Venture (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Schedule of Equity Method Investments Joint Ventures [Line Items]
Investment in equity accounted joint venture, beginning balance			$ 148,665	$ 130,660	$ 130,660
Equity contributions to joint venture entity			4,000		17,000
Share of results	$ 2,001	$ (164)	1,396	$ (3,205)	651
Distributions received from joint venture entity			(6,850)
Capitalized interest and deferred financing costs					354
Investment in equity accounted joint venture, ending balance	$ 147,211		$ 147,211		$ 148,665

Investment in Equity Accounte_5

Investment in Equity Accounted Joint Venture - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 21, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Mar. 31, 2020	Jan. 31, 2018
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		$ 6,300		$ 6,300		$ 6,500
Share of results		$ 2,001	$ (164)	1,396	$ (3,205)	$ 651
Dividend distributions from joint venture				(6,850)
Greater Bay Gas Company Limited [Member] | Pool Agency [Member]
Schedule of Equity Method Investments [Line Items]
Economic interest in building and operating marine export terminal							50.00%
Ethylene Marine Export Terminal [Member]
Schedule of Equity Method Investments [Line Items]
Amortization cost				$ 100	100
Economic interest in building and operating marine export terminal		50.00%		50.00%		50.00%		50.00%
Dividend distributions from joint venture				$ 6,900	0	$ 0
Proceeds from equity method investment distribution				6,000
Proceeds from equity method investment distribution return of capital				900
Total estimated capital cost of construction of the terminal		$ 146,500		146,500
Capital contribution to the joint venture towards construction cost	$ 4,000
Ethylene Marine Export Terminal [Member] | Enterprise Product Partners LP [Member] | Co-venturer [Member]
Schedule of Equity Method Investments [Line Items]
Economic interest in building and operating marine export terminal								50.00%
Export Terminal [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		147,200		147,200		$ 148,700
Share of results		$ 2,100	$ 100	$ 1,500	$ 3,000
Economic interest in building and operating marine export terminal								50.00%

Secured Term Loan Facilities _3

Secured Term Loan Facilities and Revolving Credit Facilities - Additional Information (Detail) - Terminal Facility [Member] - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Jan. 31, 2021	Jun. 30, 2021
Debt Instrument [Line Items]
Credit facility, amount drawn during period	$ 69
ING Capital LLC And SG America Securities [Member] | Ethylene Marine Export Terminal [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity		$ 75
ING Capital LLC And SG America Securities [Member] | Ethylene Marine Export Terminal [Member] | Maturity Of Debt Time Two [Member]
Debt Instrument [Line Items]
Date of commencement of the terminal credit facility		Mar. 29, 2019
Expiration date of line of credit facility		Dec. 31, 2025
Minimum [Member]
Debt Instrument [Line Items]
Credit facility, final payment		$ 3.1
Maximum [Member]
Debt Instrument [Line Items]
Credit facility, final payment		$ 3.8

Secured Term Loan Facilities _4

Secured Term Loan Facilities and Revolving Credit Facilities - Schedule of Breakdown of Secured Term Loan Facilities and Total Deferred Financing Costs Split Between Current and Non-Current Liabilities (Detail) - USD ($) $ in Thousands		Jun. 30, 2021	Dec. 31, 2020
Current Liability
Current portion of secured term loan facilities		$ 89,056	$ 67,936
Less: current portion of deferred financing costs		(2,341)	(2,274)
Current portion of secured term loan facilities, net of deferred financing costs		86,715	65,662
Non-Current Liability
Secured term loan facilities and revolving credit facilities net of current portion	[1]	577,427	617,994
Less: non-current portion of deferred financing costs		(3,553)	(4,183)
Non-current secured term loan facilities and revolving credit facilities, net of current portion and non-current deferred financing costs		$ 573,874	$ 613,811
[1]	Includes amounts relating to the Navigator Aurora Facility held within a lessor entity (for which legal ownership resides with a financial institution) that we are required to consolidate under U.S. GAAP into our financial statements as a variable interest entity.

Senior Secured Bond - Additiona

Senior Secured Bond - Additional Information (Detail)	Nov. 02, 2018NOK (kr)	Dec. 31, 2020USD ($)	Jun. 30, 2021NOK (kr)	Jun. 30, 2020	Jun. 30, 2021USD ($)	Dec. 31, 2018NOK (kr)	Nov. 02, 2018USD ($)
Debt Instrument [Line Items]
Minimum liquidity to be maintained, amount		$ 59,056,000			$ 96,252,000
Debt instrument covenant description		financial covenants (each as defined within the bond agreement governing the 2020 Bonds (the “2020 Bond Agreement”)) are: (a) The issuer shall ensure that the Group (meaning “the Company and its subsidiaries”) maintains a minimum liquidity of no less than $35.0 million; and (b) maintain a Group equity ratio (as defined in the 2020 Bond Agreement) of at least 30%. As of June 30, 2021, the Company was in compliance with all covenants for the 2020 Bonds​​​​​​​.	The 2020 Bond Agreement provides that we may declare or pay dividends to shareholders provided that the Company maintains a minimum liquidity of $60.0 million, unless an event of default has occurred and is continuing. The 2020 Bond Agreement also limits us and our subsidiaries from, among other things, entering into mergers and divestitures, engaging in transactions with affiliates or incurring any additional liens which would have a material adverse effect. In addition, the 2020 Bond Agreement includes customary events of default, including those relating to a failure to pay principal or interest, a breach of covenant, false representation and warranty, a cross-default to other indebtedness, the occurrence of a material adverse effect, or our insolvency or dissolution.
2018 Senior Secured Bonds [Member]
Debt Instrument [Line Items]
Aggregate principal amount | kr	kr 600,000,000		kr 600,000,000
Variable interest rate on bond	6.00%
Debt instrument maturity date	Nov. 2, 2023
Debt instrument variable rate description	The 2018 Bonds bear interest at a rate equal to the 3-month NIBOR plus 6.0% per annum, calculated on a 360-day year basis and mature on November 2, 2023.
Interest payment description on bond	Interest is payable quarterly in arrears on February 2, May 2, August 2 and November 2
Debt instrument redemption description	The Company may redeem the 2018 Bonds, in whole or in part, at any time beginning on or after November 2, 2021. Any 2018 Bonds redeemed from November 2, 2021 until November 1, 2022, are redeemable at 102.4% of par, from November 2, 2022 until May 1, 2023, are redeemable at 101.5% of par, and from May 2, 2023 to the maturity date are redeemable at 100% of par, in each case, in cash plus accrued interest.
Debt instrument covenant description			The financial covenants each as defined within the 2018 Bond Agreement are: (a) The issuer shall ensure that the Group (meaning “the Company and its subsidiaries”) maintains a minimum liquidity of no less than $25.0 million and (b) maintain a Group equity ratio of at least 30% (as defined in the 2018 Bond Agreement). At June 30, 2021, the Company was in compliance with all covenants for the 2018 Bonds.
2018 Senior Secured Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Minimum liquidity to be maintained, amount					$ 25,000,000
Gross Equity ratio			30.00%
2018 Senior Secured Bonds [Member] | November 2, 2021 through November 1, 2022 [Member]
Debt Instrument [Line Items]
Debt instrument redeemable percentage	102.40%
2018 Senior Secured Bonds [Member] | November 2, 2022 through May 1, 2023 [Member]
Debt Instrument [Line Items]
Debt instrument redeemable percentage	101.50%
2018 Senior Secured Bonds [Member] | May 2, 2023 through Maturity Date [Member]
Debt Instrument [Line Items]
Debt instrument redeemable percentage	100.00%
2018 Senior Secured Bonds [Member] | Redemption of Bonds [Member]
Debt Instrument [Line Items]
Debt instrument redeemable percentage				101.00%
Senior Secured Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Dividend payable percentage			50.00%
Nordea Bank Abp [Member] | 2018 Senior Secured Bonds [Member]
Debt Instrument [Line Items]
Aggregate principal amount						kr 600,000,000	$ 71,700,000
Debt instrument variable rate description	6.608% plus 3-month U.S. LIBOR

Senior Secured Bond - Schedule

Senior Secured Bond - Schedule of Breakdown of Senior Secured Bond and Total Deferred Financing Costs (Detail) - Senior Secured Bonds [Member] - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Total Bond	$ 69,961	$ 70,299
Less deferred financing costs	(593)	(719)
Total	$ 69,368	$ 69,580

Senior Unsecured Bond - Additio

Senior Unsecured Bond - Additional Information (Detail) - USD ($) $ in Thousands	4 Months Ended	6 Months Ended
	Dec. 31, 2020	Jun. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Debt instrument covenant description	financial covenants (each as defined within the bond agreement governing the 2020 Bonds (the “2020 Bond Agreement”)) are: (a) The issuer shall ensure that the Group (meaning “the Company and its subsidiaries”) maintains a minimum liquidity of no less than $35.0 million; and (b) maintain a Group equity ratio (as defined in the 2020 Bond Agreement) of at least 30%. As of June 30, 2021, the Company was in compliance with all covenants for the 2020 Bonds​​​​​​​.	The 2020 Bond Agreement provides that we may declare or pay dividends to shareholders provided that the Company maintains a minimum liquidity of $60.0 million, unless an event of default has occurred and is continuing. The 2020 Bond Agreement also limits us and our subsidiaries from, among other things, entering into mergers and divestitures, engaging in transactions with affiliates or incurring any additional liens which would have a material adverse effect. In addition, the 2020 Bond Agreement includes customary events of default, including those relating to a failure to pay principal or interest, a breach of covenant, false representation and warranty, a cross-default to other indebtedness, the occurrence of a material adverse effect, or our insolvency or dissolution.
Minimum liquidity to be maintained, amount	$ 59,056	$ 96,252
2020 Senior Unsecured Bonds [Member]
Debt Instrument [Line Items]
Aggregate principal amount			$ 100,000
Interest rate on bond			8.00%
Debt instrument maturity date	Sep. 10, 2025
Interest payment description on bond	Interest is payable semi-annually in arrears on March 10 and September 10.
Debt instrument covenant description		The 2020 Bonds are redeemable by the Company, in whole or in part, at any time. Any 2020 Bonds redeemed; up until September 9, 2023 will be priced at the aggregate of the net present value of 103.2% of par and interest payable up to September 9, 2023; from September 10, 2023 up until September 9, 2024, are redeemable at 103.2% of par; from September 10, 2024 up until March 9, 2025, are redeemable at 101.6% of par, and from March 10, 2025 to the maturity date are redeemable at 100% of par, in each case, in cash plus accrued interest.
2020 Senior Unsecured Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Minimum liquidity to be maintained, amount		$ 35,000
2020 Senior Unsecured Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Gross Equity ratio	30.00%
2020 Senior Unsecured Bonds [Member] | Until September 9, 2023
Debt Instrument [Line Items]
Debt instrument redeemable percentage	103.20%
2020 Senior Unsecured Bonds [Member] | September 10 ,2023 Up Until September 9 ,2024
Debt Instrument [Line Items]
Debt instrument redeemable percentage	103.20%
2020 Senior Unsecured Bonds [Member] | September 10 ,2024 Up Until September 9 ,2025
Debt Instrument [Line Items]
Debt instrument redeemable percentage	101.60%

Senior Unsecured Bond - Schedul

Senior Unsecured Bond - Schedule of Breakdown of Senior Unsecured Bond and Total Deferred Financing Costs (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
2017 Senior Unsecured Bonds [Member]
Debt Instrument [Line Items]
Total Bond	$ 100,000	$ 100,000
2020 Senior Unsecured Bonds [Member]
Debt Instrument [Line Items]
Less deferred financing costs	(1,645)	(1,842)
Total	$ 98,355	$ 98,158

Derivative Instruments Accoun_3

Derivative Instruments Accounted for at Fair Value - Additional Information (Detail) kr in Millions	Jul. 02, 2020	Nov. 02, 2018NOK (kr)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021NOK (kr)	Dec. 31, 2020USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives designated as hedges held			$ 0		$ 0			$ 0
Description of Interest Rate Derivative Activities	On July 2, 2020, the Company entered into floating-to-fixed interest rate swap agreements with ING Capital Markets LLC (“ING”) and Societe Generale (“SocGen”) with a termination date of December 31, 2025, to run concurrently with the Terminal Facility. Under these agreements, the notional amounts of the swaps are approximately 80% of the amounts drawn under the Terminal Facility.
Unrealized Gain loss on Derivatives			(269,000)	$ 6,354,000	278,000	$ (7,607,000)
Restricted Cash			0		0
Collateral amount held with swap provider			0		0
Derivative fair value of derivative asset amount offset against collateral			0		0
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of Derivative liability			2,900,000		2,900,000			$ 2,900,000
Unrealized Gain loss on Derivatives					50,000	$ 7,600,000
2018 Senior Secured Bonds [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Outstanding secured borrowings, principal | kr		kr 600					kr 600
Outstanding secured borrowings, interest rate terms		The 2018 Bonds bear interest at a rate equal to the 3-month NIBOR plus 6.0% per annum, calculated on a 360-day year basis and mature on November 2, 2023.
2018 Senior Secured Bonds [Member] | NORWAY
Derivative Instruments, Gain (Loss) [Line Items]
Outstanding secured borrowings, principal			71,700,000		71,700,000
Outstanding secured borrowings			$ 71,700,000		$ 71,700,000		kr 600
Spread on variable rate			6.608%		6.608%		6.608%	6.608%
Outstanding secured borrowings, maturity year					2023
Outstanding secured borrowings, interest rate terms					6.608% plus 3-month U.S. LIBOR
2018 Senior Secured Bonds [Member] | NORWAY | NIBOR [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Spread on variable rate			6.00%		6.00%		6.00%	6.00%
Outstanding secured borrowings, interest rate terms					6.0% plus 3-month NIBOR
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of Derivative liability								$ 100,000
Unrealized Gain loss on Derivatives					$ 200,000
Outstanding secured borrowings, interest rate terms					3-month LIBOR, calculated on a 360-day year basis, which resets every three months in line with the dates of interest payments on the Terminal Facility.
Derivative Liability, Fair Value, Gross Asset			$ 200,000		$ 200,000
Interest Rate Swap [Member] | ING And SocGen [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of Derivative			$ 200,000		$ 200,000

Derivative Instruments Accoun_4

Derivative Instruments Accounted for at Fair Value - Schedule of Estimated Fair Value and Carrying Value of Assets and Liabilities Measured at Fair Value on Recurring Basis, Non-recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Cross Currency Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Asset (Liability)	$ (2,943)	$ (2,896)
Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Asset (Liability)	$ 215	$ (111)

Fair Value of Financial Instr_3

Fair Value of Financial Instruments Not Accounted For at Fair Value - Schedule of Estimated Fair Value and Carrying Value of Assets and Liabilities Measured at Fair Value on Recurring Basis, Non-recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
2018 Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bonds, Carrying amount		$ (70,299)
Senior unsecured bond, Fair Value (Liability)		(72,672)
2020 Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior unsecured bond, Fair Value (Liability)		(103,500)
Long-term Debt, Gross		$ (100,000)
Level 2 [Member] | 2018 Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bonds, Carrying amount	$ (69,691)
Senior unsecured bond, Fair Value (Liability)	(72,759)
Level 2 [Member] | 2020 Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior unsecured bond, Fair Value (Liability)	(105,000)
Long-term Debt, Gross	$ (100,000)

Earnings per Share - Calculatio

Earnings per Share - Calculation of Basic and Diluted Number of Weighted Average Outstanding Shares (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Basic and diluted income / (loss) available to common stockholders (in thousands)	$ 260	$ 3,008	$ 3,080	$ (5,154)
Basic weighted average number of shares	55,971,121	55,905,600	55,935,859	55,871,893
Effect of dilutive potential share options:	335,436,000	348,178,000	337,674,000	0
Diluted weighted average number of shares	56,306,557	56,253,778	56,273,533	55,871,893

Earnings per Share - Calculat_2

Earnings per Share - Calculation of Basic and Diluted Number of Weighted Average Outstanding Shares (Parenthetical) (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Effect of dilutive potential shares	335,436,000	348,178,000	337,674,000	0
Potential dilutive shares excluded computation of earnings per share				349,057

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Detail) - USD ($)	Mar. 17, 2015	Mar. 31, 2021	Mar. 17, 2021	Apr. 30, 2020	Mar. 19, 2020	Jun. 30, 2021	Jun. 30, 2020	Oct. 31, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of shares				2,144
Share-based compensation costs						$ 610,849	$ 615,145
Share-based compensation costs						$ 34,926	77,364,000
Share based compensation options exercisable						335,436			339,936
weighted average exercise price of share options exercisable									$ 21.40
weighted-average remaining contractual term of options outstanding						3 years 2 months 4 days
weighted-average remaining contractual term of options exercisable									3 years 8 months 1 day
Shares granted forfieted						7,595		10,054	12,198
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	4 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 6 months
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost not yet recognized						$ 1,121,038	$ 1,002,608
Total compensation cost not yet recognized period for recognition						11 months 23 days			11 months 4 days
2013 Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average value, per share								$ 11.54
Non Employee Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of shares						7,595			27,125
Weighted average option price						$ 7.90
Non Employee Director [Member] | 2013 Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of shares		30,380	29,240		37,975
Weighted average value, per share		$ 7.90	$ 10.26			7.90			$ 11.06
Share vested, total fair value		$ 295,294							$ 114,739
Chief Executive Officer [Member] | 2013 Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of shares		91,942			17,240
Weighted average value, per share		$ 12.04				$ 7.90
Share vested, total fair value		$ 893,676							$ 265,487
Officers and Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						3 months
Share-based Compensation, expiration period						10 months
Officers and Employees [Member] | 2013 Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of shares		91,942	35,849		25,579				62,763
Weighted average value, per share		$ 12.04							$ 12.77
Share vested, total fair value		$ 893,676
Officers and Employees [Member] | 2013 Long Term Incentive Plan [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of shares			20,009
Weighted average value, per share			$ 10.26

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Share Grant Activity (Detail) - $ / shares	6 Months Ended	10 Months Ended	12 Months Ended
	Jun. 30, 2021	Oct. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Number of RSUs
Unvested, beginning balance	306,242	329,156	329,156
Granted	85,098		79,172
Forfeited	(7,595)	(10,054)	(12,198)
Vested	(122,322)		(89,888)
Unvested, ending balance	261,423		306,242	329,156
Weighted-average grant date fair value
Unvested, beginning balance	$ 10.54	$ 11.68	$ 11.68
Granted	10.26		7.90
Vested	11.01		12.25
Forfeited	7.90		11.54
Unvested, ending balance	$ 10.30		$ 10.54	$ 11.68
Weighted-average remaining contractual terms (Years)
Weighted-average remaining contractual terms (Years)	11 months 23 days		11 months 4 days	1 year 4 months 17 days

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Stock Option Activity (Detail) - $ / shares	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Options
Beginning Balance	339,936	349,936
Forfeited during the period	(4,500)	(10,000)
Ending Balance	335,436	339,936
Weighted-Average Exercise Price
Beginning Balance	$ 21.40	$ 21.39
Forfeited during the period	0	20.82
Ending Balance	$ 21.40	$ 21.40

Commitments and Contingencies -

Commitments and Contingencies - Summary of Contractual Obligations (Detail) $ in Thousands	Jun. 30, 2021USD ($)
Contractual Obligation Fiscal Year Maturity [Line Items]
2021	$ 34,623
2022	124,732
2023	274,050
2024	182,527
2025	165,274
Thereafter	58,018
Total	839,224
Navigator Aurora Facility [Member]
Contractual Obligation Fiscal Year Maturity [Line Items]
Thereafter	58,018
Total	58,018
Office operating leases [Member]
Contractual Obligation Fiscal Year Maturity [Line Items]
2021	791	[1]
2022	253	[1]
Total	1,044	[1]
Secured term loan facilities and revolving credit facilities [Member]
Contractual Obligation Fiscal Year Maturity [Line Items]
2021	33,832
2022	124,479
2023	202,353
2024	182,527
2025	65,274
Total	608,465
2018 Bonds [Member]
Contractual Obligation Fiscal Year Maturity [Line Items]
2023	71,697
Total	71,697
2020 Bonds [Member]
Contractual Obligation Fiscal Year Maturity [Line Items]
2025	100,000
Total	$ 100,000
[1]	The Company occupies office space in London with a lease that commenced in January 2017 for a period of 10 years with a mutual break option in January 2022. The break option was exercised by the Company on April 22, 2021. Please read Note 14—Operating Lease Liabilities for additional information. The Company entered into a three-year lease for office space in New York that terminates on May 31, 2022. The annual gross rent under this lease is approximately $0.4 million, subject to certain adjustments. The lease term for our representative office in Gdynia, Poland is for a period of five years commencing from January 2017. The gross rent per year is approximately $60,000. The weighted average remaining contractual lease term for the above three office leases on June 30, 2021, was 0.68 years.

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2021	Apr. 22, 2021	Dec. 31, 2020
Schedule Of Commitments And Contingencies [Line Items]
Weighted Average Remaining Lease Tenure	8 months 4 days		5 years 7 months 6 days
Office Space [Member]
Schedule Of Commitments And Contingencies [Line Items]
Weighted Average Remaining Lease Tenure	8 months 4 days
POLAND [Member]
Schedule Of Commitments And Contingencies [Line Items]
Lease term	5 years
Operating lease future minimum payment per year	$ 60,000
London [Member]
Schedule Of Commitments And Contingencies [Line Items]
Lease term	10 years	10 years
NEW YORK [Member]
Schedule Of Commitments And Contingencies [Line Items]
Operating lease future minimum payment per year	$ 400,000
Lease expiration date	May 31, 2022

Operating Lease Liabilities - A

Operating Lease Liabilities - Additional Information (Detail)	Jun. 30, 2021	Apr. 22, 2021	Dec. 31, 2020
Operating Lease Weighted Average Discount Rate	3.98%
Remaing Lease Period	8 months 4 days		5 years 7 months 6 days
UNITED KINGDOM | Accounting Standards Update 2016-02 [Member]
Lessee, Operating Lease, Term of Contract		5 years
Lessee, Operating Lease, Discount Rate		3.12%
London [Member]
Lessee, Operating Lease, Term of Contract	10 years	10 years

Operating Lease Liabilities - M

Operating Lease Liabilities - Maturity Analysis of The Annual Undiscounted Cash Flows of The Company's Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Operating Lease Liabilities [Abstract]
One year	$ 1,044	$ 1,572
Two year	0	1,300
Three year	0	1,144
Four year	0	1,144
Five year	0	1,144
Six years and thereafter	0	1,222
Total undiscounted operating lease commitments	1,044	7,526
Less: Discount adjustment	(36)	(1,018)
Total operating lease liabilities	1,008	6,508
Less: current portion	(1,008)	(1,276)
Operating lease liabilities, non-current portion		$ 5,232

Cash,Cash Equivalents and Restr

Cash,Cash Equivalents and Restricted Cash - Schedule of breakdown of cash, cash equivalents and restricted cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Cash, Cash Equivalents and Restricted Cash
Cash and cash equivalents	$ 96,252	$ 59,056
Cash and Cash equivalents held by the lessor VIE	96,356	59,271
Restricted cash
Total cash, cash equivalents and restricted cash	96,356	59,271
Variable Interest Entity, Primary Beneficiary [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash equivalents held by the lessor VIE	104	215
Total cash, cash equivalents and restricted cash	$ 104	$ 215

Cash,Cash Equivalents and Res_2

Cash,Cash Equivalents and Restricted Cash - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Cash, cash equivalents and restricted cash	$ 96,356	$ 59,271
Variable Interest Entity, Primary Beneficiary [Member]
Cash, cash equivalents and restricted cash	$ 104	$ 215

Variable Interest Entities - Ad

Variable Interest Entities - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Oct. 31, 2019	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Line of Credit Facility [Line Items]
Sale value of property	$ 77,500
Proceeds from sale of property in percent to sale value	90.00%
Proceeds from sale of property in value to sale value	$ 69,750
Credit from sale of property in percent to sale value	10.00%
Repayment of secured debt	$ 44,500
Bareboat charter agreement period	13 years
Bareboat charter agreement description	the Company entered into a bareboat charter for the vessel for a period of up to 13 years, with purchase options at years 5, 7 and 10.
Variable interest entity, consolidated, carrying amount, assets		$ 1,828,817		$ 1,828,817		$ 1,839,408
Variable interest entity, consolidated, carrying amount, liabilities		881,949		881,949		897,013
Interest expense		8,647	$ 11,128	17,608	$ 22,668
Payments to Acquire Businesses, Gross				$ 323	982
Common Stock [Member]
Line of Credit Facility [Line Items]
Variable Interest Entity, consolidated				49.00%
Ocean Yield Arora Ltd [Member]
Line of Credit Facility [Line Items]
Variable interest entity, consolidated, carrying amount, assets		91,000		$ 91,000		63,500
Variable interest entity, consolidated, carrying amount, liabilities		58,400		58,400		61,700
Variable Interest Entity, Primary Beneficiary [Member]
Line of Credit Facility [Line Items]
Variable interest entity, consolidated, carrying amount, assets		135,400		135,400		125,900
Variable interest entity, consolidated, carrying amount, liabilities		16,900		16,900		$ 9,500
Interest expense		$ 300	$ 500	600	1,100
Proceeds from Related Party Debt				3,300	$ 3,700
Payments to Acquire Businesses, Gross				$ 44,800
Variable Interest Entity, Primary Beneficiary [Member] | PT Navigator Khatulistiwa [Member]
Line of Credit Facility [Line Items]
Variable Interest Entity, consolidated				100.00%		100.00%

Variable Interest Entities - Sc

Variable Interest Entities - Schedule of Assets and Liabilities of the Lessor VIE (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets [Abstract]
Cash, cash equivilents and restricted cash	$ 96,356	$ 59,271
Liabilities [Abstract]
Amounts due to related parties, current	(206)	(229)
Amounts due to related parties, non-current	(57,881)	(61,219)
Variable Interest Entity, Primary Beneficiary [Member]
Assets [Abstract]
Cash, cash equivilents and restricted cash	104	215
Liabilities [Abstract]
Amounts due to related parties, current	(206)	(229)
Amounts due to related parties, non-current	(58,018)	(61,361)
Total liabilities	$ (58,224)	$ (61,590)

Related Party Transactions - Sc

Related Party Transactions - Schedule of Related Party Transactions Income Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Schedule of Related Party Transactions Income Expenses [Line Items]
Net income / (expenses)	$ (308)	$ (6,554)	$ (623)	$ 5,923
Luna Pool Agency Limited [Member]
Schedule of Related Party Transactions Income Expenses [Line Items]
Net income / (expenses)	15,215	7,045	27,499	7,045
Ocean Yield Malta Limited [Member]
Schedule of Related Party Transactions Income Expenses [Line Items]
Net income / (expenses)	$ (308)	$ (491)	$ (623)	$ (1,122)

Related Party Transactions - _2

Related Party Transactions - Schedule Of Balances Due To And From Related Parties (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Luna Pool Agency Limited [Member]
Schedule Of Balances Due To And From Related Parties [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 5,923	$ 11,853
Ocean Yield Malta Limited [Member]
Schedule Of Balances Due To And From Related Parties [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ (58,087)	$ (61,448)

Related Party Transactions - Di

Related Party Transactions - Disclosure Of Operating Results On Account Of Related Party Transactions (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disclosure Of Operating Results On Account Of Related Party Transactions [Line Items]
Voyage expenses	$ 17,689	$ 14,728	$ 33,305	$ 32,272
Total net operating income from the Luna Pool	7,366	13,353	19,700	22,687
Total net income from the Luna Pool	(308)	(6,554)	(623)	5,923
Luna Pool Agency Limited [Member]
Disclosure Of Operating Results On Account Of Related Party Transactions [Line Items]
Time and Voyage charter revenues	24,909	10,246	43,790	10,246
Time and Voyage charter revenues from Luna Pool collaborative arrangement	5,546	2,596	10,785	2,596
Brokerage commissions	(432)	(170)	(708)	(170)
Voyage expenses	(9,233)	(2,701)	(16,732)	(2,701)
Voyage expenses – Luna Pool collaborative arrangement	(5,663)	(3,043)	(9,796)	(3,043)
Total net operating income from the Luna Pool	15,127	6,928	27,339	6,928
Other income	88	117	160	117
Total net income from the Luna Pool	15,215	7,045	27,499	7,045
Ocean Yield Malta Limited [Member]
Disclosure Of Operating Results On Account Of Related Party Transactions [Line Items]
Total net income from the Luna Pool	(308)	(491)	(623)	(1,122)
Related Party Transaction, Amounts of Transaction	(304)	(489)	(623)	(1,122)
Ocean Yield Malta Limited [Member] | General and Administrative Costs [Member]
Disclosure Of Operating Results On Account Of Related Party Transactions [Line Items]
Related Party Transaction, Amounts of Transaction		(7)	(4)	(9)
Ocean Yield Malta Limited [Member] | Interest Expense [Member]
Disclosure Of Operating Results On Account Of Related Party Transactions [Line Items]
Related Party Transaction, Amounts of Transaction	$ (304)	$ (482)	$ (619)	$ (1,113)

Related Party Transactions - _3

Related Party Transactions - Disclosure Details Of Balance Due From To Related Parties (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Luna Pool Agency Limited [Member]
Related Party Transaction [Line Items]
Other assets	$ 5,923	$ 11,853
Total assets (liabilities)	5,923	11,853
Ocean Yield Malta Limited [Member]
Related Party Transaction [Line Items]
Accrued interest and trade payables	(206)	(229)
Navigator Aurora Facility, net of deferred financing costs	(57,878)	(61,216)
Other non-current payables	(3)	(3)
Total assets (liabilities)	$ (58,087)	$ (61,448)

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
	Oct. 31, 2019	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Due to Related Parties, Current		$ 206		$ 229
Prepayment of Loan		4,000	$ 7,500
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Prepayment of Loan		3,300
OCY Aurora Limited [Member]
Maximum amount of potential future payments under the guarantee		54,400
Navigator Aurora Facility [Member] | OCY Aurora Limited [Member]
Line of credit maximum borrowing capacity	$ 69,100
Debt instrument variable interest rate spread percentage	185.00%
Due to Related Parties, Current		58,000		61,400
Value Of Security In Excess Of Loan Borrowed Cumulative Gain		$ 18,400		$ 14,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] $ / shares in Units, $ in Thousands, shares in Millions	Oct. 07, 2021USD ($)	Aug. 04, 2021USD ($)VesselsVessel$ / sharesshares
Subsequent Event [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt		$ 192,700
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		$ 17,500
London [Member]
Subsequent Event [Line Items]
Lease commencement month description	January 2022
Lease expiration period	10 years
Annual lease cost	$ 1,100
Rent free period	27 months
Total commitment amount payable termination of lease	$ 4,300
Lease commitment amount full tenor of lease period	$ 8,600
Ultranav [Member]
Subsequent Event [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares		21.2
Business Acquisition, Share Price | $ / shares		$ 9.57
Debt Instrument, Periodic Payment, Principal		$ 13,600
Business combination debt acquired maturity beginning month		2026-06
Business combination number of vessels secured by loan agrement | Vessels		13
Derivative, Swaption Interest Rate		2.00%
Business Combination Recognized Identifiable Asset s Acquired And Liabilities Assumed Net Asseyts Other Than Property Plant And Equipment		$ 1,400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables		7,100
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory		2,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other		5,600
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Investment In Associated Companies		1,500
Business combination recognized identifiable assets acquired and liabilities assumed accounts payable and accruals		8,800
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities		6,000
Vessels In Operation Member [Member] | Happy Bride Six Thousand And Fourhundred CBM Lpg Built Carrier [Member]
Subsequent Event [Line Items]
Disposal Group, Including Discontinued Operation, Consideration		4,750
Vessels In Operation Member [Member] | Ultranav [Member]
Subsequent Event [Line Items]
Business combination assets acquired and liabilities assumed equipment		$ 377,000
Business Combination Number Of Equipments Acquired | Vessels		18
Business combination number of entities acquired | Vessel		2
Vessels In Operation Member [Member] | Ultranav [Member] | Twenty Two Thousand CBM Handy Semi Refrigerated Vessels [Member]
Subsequent Event [Line Items]
Business Combination Number Of Equipments Acquired | Vessels		7
Vessels In Operation Member [Member] | Ultranav [Member] | Five Twelve Thousand And CBM Ethylene Vessels [Member]
Subsequent Event [Line Items]
Business Combination Number Of Equipments Acquired | Vessels		5
Vessels In Operation Member [Member] | Ultranav [Member] | Six Gas Carriers Three Thousand Seven Hundred And Seventy To Nine Thousand Range [Member]
Subsequent Event [Line Items]
Business Combination Number Of Equipments Acquired | Vessels		6
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Ultranav [Member]
Subsequent Event [Line Items]
Debt instrument variable interest rate spread percentage		1.90%
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | Ultranav [Member]
Subsequent Event [Line Items]
Debt instrument variable interest rate spread percentage		2.65%