Real Estate Investments Business Acquisitions (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Purchase Price	$ 222,000
Debt assumed, net of premiums	111,175
Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	14,768
Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 7,467
Country Walk Plaza [Member]
Business Acquisition [Line Items]
Date Purchased		Jan. 01, 2020
Property Name		Country Walk Plaza
City/State		Miami, FL
Ownership		100.00%
Purchase Price		$ 39,625
Debt assumed, net of premiums		16,359
Country Walk Plaza [Member] \| Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets		3,294
Country Walk Plaza [Member] \| Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets		$ 2,452
Willa Springs [Member]
Business Acquisition [Line Items]
Date Purchased	Jul. 30, 2021
Property Name	Willa Springs
City/State	Winter Springs, FL
Ownership	100.00%
Purchase Price	$ 34,500
Debt assumed, net of premiums	17,682
Willa Springs [Member] \| Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	1,562
Willa Springs [Member] \| Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 643
Dunwoody Hall [Member]
Business Acquisition [Line Items]
Date Purchased	Aug. 01, 2021
Property Name	Dunwoody Hall
City/State	Dunwoody, GA
Ownership	100.00%
Purchase Price	$ 32,000
Debt assumed, net of premiums	14,612
Dunwoody Hall [Member] \| Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	2,255
Dunwoody Hall [Member] \| Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 973
Alden Bridge [Member]
Business Acquisition [Line Items]
Date Purchased	Aug. 01, 2021
Property Name	Alden Bridge
City/State	Woodlands, TX
Ownership	100.00%
Purchase Price	$ 43,000
Debt assumed, net of premiums	27,529
Alden Bridge [Member] \| Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	3,198
Alden Bridge [Member] \| Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 2,308
Hasley Canyon Village [Member]
Business Acquisition [Line Items]
Date Purchased	Aug. 01, 2021
Property Name	Hasley Canyon Village
City/State	Castaic, CA
Ownership	100.00%
Purchase Price	$ 31,000
Debt assumed, net of premiums	16,941
Hasley Canyon Village [Member] \| Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 2,037
Shiloh Springs [Member]
Business Acquisition [Line Items]
Date Purchased	Aug. 01, 2021
Property Name	Shiloh Springs
City/State	Garland, TX
Ownership	100.00%
Purchase Price	$ 19,500
Shiloh Springs [Member] \| Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	1,825
Shiloh Springs [Member] \| Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 1,079
Bethany Park Place [Member]
Business Acquisition [Line Items]
Date Purchased	Aug. 01, 2021
Property Name	Bethany Park Place
City/State	Allen, TX
Ownership	100.00%
Purchase Price	$ 18,000
Debt assumed, net of premiums	10,800
Bethany Park Place [Member] \| Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	996
Bethany Park Place [Member] \| Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 1,732
Blossom Valley [Member]
Business Acquisition [Line Items]
Date Purchased	Aug. 01, 2021
Property Name	Blossom Valley
City/State	Mountain View, CA
Ownership	100.00%
Purchase Price	$ 44,000
Debt assumed, net of premiums	23,611
Blossom Valley [Member] \| Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	2,895
Blossom Valley [Member] \| Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 732

Business Acquisition Location, City and State

No definition available.

Name:	reg_BusinessAcquisitionLocationCityAndState
Namespace Prefix:	reg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the acquirer obtains control of the acquiree, in YYYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=123586518&loc=d3e848-128460

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=123586518&loc=d3e845-128460

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionEffectiveDateOfAcquisition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
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_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Name of the acquired entity.

+ 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 (a)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

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

- 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:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of identifiable intangible assets recognized as of the acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 55
-Paragraph 37
-URI http://asc.fasb.org/extlink&oid=123455525&loc=d3e2207-128464

Reference 2: 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=123413009&loc=d3e4845-128472

+ Details

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

- Definition

Amount of liabilities 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=123413009&loc=d3e4845-128472

+ Details

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

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_OffMarketFavorableLeaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	reg_FiniteLivedIntangibleLiabilitiesAxis=reg_OffMarketLeaseUnfavorableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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