Debt Covenant Cash Amount, Condition One

No definition available.

Name:	rgls_DebtCovenantCashAmountConditionOne
Namespace Prefix:	rgls_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt Covenant Cash Amount, Condition Two

+ References

No definition available.

+ Details

Name:	rgls_DebtCovenantCashAmountConditionTwo
Namespace Prefix:	rgls_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt, Interest Only Payment Fee

+ References

No definition available.

+ Details

Name:	rgls_DebtInterestOnlyPaymentFee
Namespace Prefix:	rgls_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Debt, Maturity Extension Fee

+ References

No definition available.

+ Details

Name:	rgls_DebtMaturityExtensionFee
Namespace Prefix:	rgls_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Minimum Cash, Debt Covenant

+ References

No definition available.

+ Details

Name:	rgls_MinimumCashDebtCovenant
Namespace Prefix:	rgls_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of Monthly Payments

+ References

No definition available.

+ Details

Name:	rgls_NumberofMonthlyPayments
Namespace Prefix:	rgls_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Payment Fee

+ References

No definition available.

+ Details

Name:	rgls_PaymentFee
Namespace Prefix:	rgls_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Prepayment Requirement of Loan From License Fees

+ References

No definition available.

+ Details

Name:	rgls_PrepaymentRequirementofLoanFromLicenseFees
Namespace Prefix:	rgls_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Prepayment Requirement of Loan From License Fees, Amount

+ References

No definition available.

+ Details

Name:	rgls_PrepaymentRequirementofLoanFromLicenseFeesAmount
Namespace Prefix:	rgls_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Revenue Recognition, Milestone Method, Potential Milestone Receivable

+ References

No definition available.

+ Details

Name:	rgls_RevenueRecognitionMilestoneMethodPotentialMilestoneReceivable
Namespace Prefix:	rgls_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Upfront Payment Received

+ References

No definition available.

+ Details

Name:	rgls_UpfrontPaymentReceived
Namespace Prefix:	rgls_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the fee that accompanies borrowing money under the debt instrument.

+ References

+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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

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

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-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

+ Details

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

- Definition

Amount of cash inflow from issuance of long-term debt classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=rgls_DebtFinancingAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rgls_DebtFinancingAgreementTrancheAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rgls_FourthAmendmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rgls_SeventhAmendmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rgls_EightAmendmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rgls_EightAmendmentMilestonePaymentMember
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:

Term Loan (Details) $ in Thousands					1 Months Ended
Term Loan (Details) $ in Thousands	May 03, 2019 USD ($)	Apr. 09, 2019 USD ($)	Jun. 22, 2016 USD ($)	Jun. 17, 2016 number_of_payment	Mar. 31, 2019 USD ($)	Nov. 30, 2018 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	May 07, 2019 USD ($)	Nov. 05, 2018 USD ($)
Debt Instrument [Line Items]
Upfront payment received					$ 1,800	$ 2,500
Debt Financing Agreement
Debt Instrument [Line Items]
Stated interest rate, percentage				8.51%
Number of monthly payments \| number_of_payment				24
Long-term debt								$ 14,700
Debt fee								1,900
Debt issuance costs								$ 100
Debt instrument effective rate								8.98%
Debt Financing Agreement \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate, percentage				0.44%
Debt Financing Agreement Tranche A
Debt Instrument [Line Items]
Proceeds from borrowing under term loan			$ 20,000
Long-term debt							$ 14,681
Fourth Amendment
Debt Instrument [Line Items]
Prepayment requirement of loan from license fees										25.00%
Potential revenue through milestone payments										$ 10,000
Prepayment requirement of loan from license fees amount					$ 400	$ 600
Payment fee										5.50%
Seventh Amendment
Debt Instrument [Line Items]
Minimum cash, debt covenant		$ 10,000
Debt covenant, condition two		10,000
Debt covenant, condition one		5,000
Eight Amendment
Debt Instrument [Line Items]
Interest only payment fee	$ 100
Maturity extension fee	$ 700
Minimum cash, debt covenant									$ 20,000
Eight Amendment - Milestone Payment
Debt Instrument [Line Items]
Minimum cash, debt covenant		$ 10,000
Minimum \| Seventh Amendment
Debt Instrument [Line Items]
Prepayment requirement of loan from license fees		25.00%
Prepayment requirement of loan from license fees amount		$ 5,000
Minimum \| Eight Amendment
Debt Instrument [Line Items]
Prepayment requirement of loan from license fees		75.00%
Maximum \| Seventh Amendment
Debt Instrument [Line Items]
Prepayment requirement of loan from license fees		75.00%
Maximum \| Eight Amendment
Debt Instrument [Line Items]
Prepayment requirement of loan from license fees		100.00%