Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

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- Definition

Business Acquisition, Cost of Entity Acquired, Purchase Price

+ References

No definition available.

+ Details

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- Definition

Area of land held.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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- 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/presentationRef

-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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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- 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.

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Balance Type:	credit
Period Type:	instant

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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Subsequent Events - Additional Information (Detail) $ in Millions	Oct. 23, 2015	Oct. 15, 2015 USD ($)	Oct. 14, 2015 USD ($) a	Oct. 02, 2015 USD ($)	Oct. 01, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2014
Subsequent Event [Line Items]
Debt Instrument, Interest Rate, Effective Percentage						3.60%	3.70%
Retreat at West Creek [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Area of Land \| a			4.4
Business Acquisition, Cost of Entity Acquired, Purchase Price			$ 3.0
Unsecured Debt [Member]
Subsequent Event [Line Items]
Debt Instrument, Interest Rate, Effective Percentage						3.80%
Unsecured Debt [Member] \| KeyBank Term Loan [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount						$ 150.0
Debt Instrument, Interest Rate, Effective Percentage						1.35%
Unsecured Debt [Member] \| KeyBank Term Loan [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	1.10%
Unsecured Debt [Member] \| $750 million unsecured revolving credit facility [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 750.0
Debt Instrument, Interest Rate, Effective Percentage		1.00%
Fixed Rate Debt \| Unsecured Debt [Member] \| Public Income Notes [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount						$ 1,000.0
Fixed Rate Debt \| Unsecured Debt [Member] \| Public Income Notes [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount					$ 184.9
Interest Rate Forward Swap [Member]
Subsequent Event [Line Items]
Derivative, Notional Amount						$ 150.0
Interest Rate Forward Swap [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Derivative, Notional Amount				$ 50.0
Maximum [Member] \| Unsecured Debt [Member] \| $750 million unsecured revolving credit facility [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,500.0