Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity.

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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Carrying amount of the equity interests owned by noncontrolling partners in an operating partnership included in the entity's consolidated financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestInOperatingPartnerships
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4568740-111683

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 55
-Paragraph 4I
-URI http://asc.fasb.org/extlink&oid=84234705&loc=SL4590271-111686

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4568447-111683

+ Details

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

- Definition

Carrying amount, attributable to parent, of an entity's issued and outstanding stock which is not included within permanent equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. Includes stock with a put option held by an ESOP and stock redeemable by a holder only in the event of a change in control of the issuer.

+ References

No definition available.

+ Details

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

- Details

Name:	srt_RestatementAxis=srt_ScenarioPreviouslyReportedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RestatementAxis=srt_RestatementAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_NoncontrollingInterestMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Adoption of ASU 2016-15 (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common shares of beneficial interest	$ 899,234	$ 900,097	$ 908,905
Noncontrolling interests – consolidated real estate entities	6,747	8,888	9,204
Redeemable noncontrolling interests - consolidated real estate entities	5,968	6,644	7,117
Total equity	643,449	687,563	636,158	$ 718,262	$ 740,954
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common shares of beneficial interest		907,843	916,121
Noncontrolling interests – consolidated real estate entities		1,078	1,924
Redeemable noncontrolling interests - consolidated real estate entities		6,708	7,181
Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common shares of beneficial interest		(7,746)	(7,216)
Noncontrolling interests – consolidated real estate entities		7,810	7,280
Redeemable noncontrolling interests - consolidated real estate entities		(64)	(64)
Common Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity	899,234	900,097	908,905	922,084	951,868
Common Stock \| Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity		907,843	916,121
Common Stock \| Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity		(7,746)	(7,216)
Noncontrolling Interest
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity	$ 74,663	81,900	82,437	$ 99,504	$ 88,844
Noncontrolling Interest \| Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity		74,090	75,157
Noncontrolling Interest \| Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity		$ 7,810	$ 7,280