Derivative Financial Instruments and Concentrations of Credit Risk - Fair Value and Notional Amounts of Credit Default Swaps (Detail) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Credit Default Swaps [Member]
Derivatives, Fair Value [Line Items]
Credit spread basis points, Minimum	281.00%
Credit spread basis points, Maximum	44.00%
Man-AHL Diversified Trading Company L.P. [Member] \| Swap Agreements - Short [Member]
Derivatives, Fair Value [Line Items]
Credit default swaps, Fair Value	$ (19,033,915)	$ (24,388,907)
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Credit Spread in Basis Points 0-100 [Member]
Derivatives, Fair Value [Line Items]
Credit spread basis points, Minimum	0.00%
Credit spread basis points, Maximum	100.00%
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Credit Spread in Basis Points 101-250 [Member]
Derivatives, Fair Value [Line Items]
Credit spread basis points, Minimum	101.00%
Credit spread basis points, Maximum	250.00%
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Credit Spread in Basis Points 251-350 [Member]
Derivatives, Fair Value [Line Items]
Credit spread basis points, Minimum	251.00%
Credit spread basis points, Maximum	350.00%
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Credit Spread in Basis Points 351-450 [Member]
Derivatives, Fair Value [Line Items]
Credit spread basis points, Minimum	351.00%
Credit spread basis points, Maximum	450.00%
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Credit Spread in Basis Points 450+ [Member]
Derivatives, Fair Value [Line Items]
Credit spread basis points, Minimum	450.00%
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Swap Agreements - Short [Member]
Derivatives, Fair Value [Line Items]
Credit default swaps, Fair Value	$ (19,593)	2,500,929
Credit default swaps, Notional Amount	5,000,000
Credit default swaps, Notional Amount		210,000,000
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Swap Agreements - Short [Member] \| Credit Spread in Basis Points 0-100 [Member]
Derivatives, Fair Value [Line Items]
Credit default swaps, Fair Value	(19,593)	641,489
Credit default swaps, Notional Amount	5,000,000
Credit default swaps, Notional Amount		175,000,000
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Swap Agreements - Short [Member] \| Credit Spread in Basis Points 101-250 [Member]
Derivatives, Fair Value [Line Items]
Credit default swaps, Fair Value	0	237,204
Credit default swaps, Notional Amount	0
Credit default swaps, Notional Amount		20,000,000
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Swap Agreements - Short [Member] \| Credit Spread in Basis Points 251-350 [Member]
Derivatives, Fair Value [Line Items]
Credit default swaps, Fair Value	0	1,622,236
Credit default swaps, Notional Amount	0
Credit default swaps, Notional Amount		15,000,000
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Swap Agreements - Short [Member] \| Credit Spread in Basis Points 351-450 [Member]
Derivatives, Fair Value [Line Items]
Credit default swaps, Fair Value	0	0
Credit default swaps, Notional Amount	0
Credit default swaps, Notional Amount		0
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| Swap Agreements - Short [Member] \| Credit Spread in Basis Points 450+ [Member]
Derivatives, Fair Value [Line Items]
Credit default swaps, Fair Value	0	0
Credit default swaps, Notional Amount	$ 0
Credit default swaps, Notional Amount		$ 0
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| 1-5 Years [Member] \| Minimum [Member]
Derivatives, Fair Value [Line Items]
Derivative remaining maturity	1 year	1 year
Man-AHL Diversified Trading Company L.P. [Member] \| Credit Default Swaps [Member] \| 1-5 Years [Member] \| Maximum [Member]
Derivatives, Fair Value [Line Items]
Derivative remaining maturity	5 years	5 years

Maximum amount of credit spread for open credit default swaps sold.

No definition available.

Name:	madl_CreditSpreadMaximum
Namespace Prefix:	madl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Minimum amount of credit spread for open credit default swaps sold.

+ References

No definition available.

+ Details

Name:	madl_CreditSpreadMinimum
Namespace Prefix:	madl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Nominal or face amount used to calculate payments on the derivative asset.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeAssetNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Nominal or face amount used to calculate payments on the derivative liability.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeLiabilityNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeRemainingMaturity1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
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

Name:	us-gaap_DerivativesFairValueLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Value of the investment at close of period. For schedules of investments that are categorized, the value would be aggregated by category. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-12C.Column C.7)
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611225-123010

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 6
-Subparagraph (SX 210.12-14.Column E.2,3)
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611322-123010

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-12.Column C.3,4)
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611133-123010

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 5
-Subparagraph (SX 210.12-13.Column C.6)
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611282-123010

+ Details

Name:	us-gaap_InvestmentOwnedAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_CreditDerivativesByContractTypeAxis=us-gaap_CreditDefaultSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=madl_ManAhlDiversifiedTradingCompanyLPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=madl_SwapContractsShortMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=madl_CreditSpreadOnUnderlyingBasisPointsOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=madl_CreditSpreadOnUnderlyingBasisPointsTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=madl_CreditSpreadOnUnderlyingBasisPointsThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=madl_CreditSpreadOnUnderlyingBasisPointsFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=madl_CreditSpreadOnUnderlyingBasisPointsFiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=madl_DerivativeInstrumentsOneToFiveYearsMaturityPeriodMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- 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: