Debt (Senior Secured Credit Facility) (Details)	12 Months Ended
Dec. 31, 2017 USD ($)
Amended Facility [Member] \| Accordion [Member]
Debt Instrument [Line Items]
Credit facility aggregate maximum borrowing capacity	$ 2,000,000,000
Senior Secured Credit Facility [Member]
Debt Instrument [Line Items]
Commitment fee percentage	0.50%
Senior secured credit facility, amount outstanding	$ 1,099,200,000.0
Total amount available for borrowings, remaining borrowing capacity	599,800,000
Senior Secured Credit Facility [Member] \| Petroleum Products [Member]
Debt Instrument [Line Items]
Senior secured credit facility, amount outstanding	$ 29,000,000
Senior Secured Credit Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Commitment fee percentage	0.50%
Debt instrument covenant, requirement leverage ratio	1.00
Debt instrument covenant, requirement senior secured leverage ratio	1.00
Debt instrument covenant, requirement interest coverage ratio	1.00
Senior Secured Credit Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Commitment fee percentage	0.25%
Debt instrument covenant, requirement leverage ratio	5.75
Debt instrument covenant, requirement senior secured leverage ratio	3.75
Debt instrument covenant, requirement interest coverage ratio	3.00
Senior Secured Credit Facility [Member] \| Acquisition Period \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument covenant, requirement interest coverage ratio	1.00
Senior Secured Credit Facility [Member] \| Acquisition Period \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument covenant, requirement interest coverage ratio	2.75
Senior Secured Credit Facility [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Letter of credit, fee percentage	2.75%
Letters of credit, outstanding amount	$ 1,000,000
Senior Secured Credit Facility [Member] \| Letter of Credit [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Letters of credit, outstanding amount	100,000,000
Senior Secured Credit Facility [Member] \| Amended Facility [Member]
Debt Instrument [Line Items]
Senior secured credit facility, maximum borrowing capacity	1,700,000,000
Senior Secured Credit Facility [Member] \| Amended Facility [Member] \| Accordion [Member]
Debt Instrument [Line Items]
Senior secured credit facility, maximum borrowing capacity	$ 300,000,000
Federal Funds Effective Rate [Member]
Debt Instrument [Line Items]
Interest rate spreads senior secured credit facility	0.50%
Federal Funds Effective Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Interest rate spreads senior secured credit facility	1.00%
LIBOR Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Interest rate spreads senior secured credit facility	1.00%
Eurodollar Rate [Member]
Debt Instrument [Line Items]
Interest rate spreads senior secured credit facility	2.75%
Eurodollar Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Interest rate spreads senior secured credit facility	1.50%
Letter of credit, fee percentage	3.00%
Eurodollar Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Interest rate spreads senior secured credit facility	3.00%
Letter of credit, fee percentage	1.50%
Alternate Base Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Letter of credit, fee percentage	2.00%
Alternate Base Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Letter of credit, fee percentage	0.50%
Applicable Margin [Member]
Debt Instrument [Line Items]
Interest rate spreads senior secured credit facility	1.75%

Under the credit facility, the interest coverage ratio as defined must exceed this specified level.

No definition available.

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Namespace Prefix:	gel_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Under the credit facility, the leverage ratio as defined cannot exceed this specified level.

+ References

No definition available.

+ Details

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Namespace Prefix:	gel_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Under the credit facility, the senior secured leverage ratio as defined cannot exceed this specified level.

+ References

No definition available.

+ Details

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Namespace Prefix:	gel_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

The annual rate paid for the use of letters of credit.

+ References

No definition available.

+ Details

Name:	gel_LetterOfCreditFeePercentage
Namespace Prefix:	gel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility, aggregate maximum borrowing capacity after accordion feature adjustment.

+ References

No definition available.

+ Details

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Namespace Prefix:	gel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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- Details

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- Details

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- Details

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- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
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- Details

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- Details

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- Details

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- Details

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