Business Acquisition (Details Textual) - USD ($)	Mar. 31, 2019	Jan. 14, 2019
Business Acquisition (Textual)
Aggregate equity interest percentage	100.00%
Pollen Gear LLC [Member]
Business Acquisition (Textual)
Operating company acquired percentage		100.00%
Aggregate equity interest percentage		4.00%
Accounts receivable		$ 550,000
Vendor deposits		$ 1,700,000

No definition available.

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

- Definition

Vendor deposits.

+ References

No definition available.

+ Details

Name:	gnln_VendorDeposits
Namespace Prefix:	gnln_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of liabilities incurred for goods and services received that are used in an entity's business and related party payables, assumed at the acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage of equity in the acquiree held by the acquirer immediately before the acquisition date in a business combination.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionAxis=gnln_PollenGearLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: