No definition available.

Name:	gnln_EquitybasedCompensationTextualAbstract
Namespace Prefix:	gnln_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Unrecognized compensation expense related to unvested Common Units.

+ References

No definition available.

+ Details

Name:	gnln_UnrecognizedCompensationExpenseRelatedToUnvestedCommonUnits
Namespace Prefix:	gnln_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Unrecognized compensation expense related to unvested common units weighted-average period.

+ References

No definition available.

+ Details

Name:	gnln_UnrecognizedCompensationExpenseRelatedToUnvestedCommonUnitsWeightedaveragePeriod
Namespace Prefix:	gnln_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Unrecognized compensation expense related to unvested stock options.

+ References

No definition available.

+ Details

Name:	gnln_UnrecognizedCompensationExpenseRelatedToUnvestedStockOptions
Namespace Prefix:	gnln_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Unrecognized Compensation Expense Related To Unvested Stock Options Weighted-Average Period.

+ References

No definition available.

+ Details

Name:	gnln_UnrecognizedCompensationExpenseRelatedToUnvestedStockOptionsWeightedAveragePeriod
Namespace Prefix:	gnln_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares authorized for issuance under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Value of forfeited shares issued under share-based payment arrangement. Excludes employee stock ownership plan (ESOP).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph c(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationForfeited
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=gnln_TwoThousandNineteenEquityIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OptionIndexedToIssuersEquityTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Compensation Plans (Details) - USD ($) $ in Millions			3 Months Ended
Compensation Plans (Details) - USD ($) $ in Millions	Aug. 20, 2019	Apr. 23, 2019	Mar. 31, 2020	Mar. 31, 2019
Equity-Based Compensation (Textual)
Share-based payment arrangement, expense				$ 2.9
Unrecognized compensation expense related to unvested stock options			$ 2.6
Unrecognized compensation expense, weighted-average period			4 years 4 months 24 days
Unrecognized compensation expense related to unvested common units			$ 3.5
Unrecognized compensation expense related to unvested common units weighted-average period			2 years 2 months 12 days
Minimum
Equity-Based Compensation (Textual)
Vesting period	4 years	0 years
Maximum
Equity-Based Compensation (Textual)
Vesting period	10 years	4 years
Equity Incentive Plan
Equity-Based Compensation (Textual)
Number of shares authorized (in shares)			5,000,000
Employee Stock \| Stock option
Equity-Based Compensation (Textual)
Share-based payment arrangement, expense			$ 0.4
Common Stock
Equity-Based Compensation (Textual)
Share-based payment arrangement, expense			0.7
Shares forfeited, value			$ 0.8