The percentage of debt offering price at par value during the period.

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- Definition

Debt Instrument, Terms, Extension Period

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Debt Instrument, Terms, Number Of Extension Options

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The number of outstanding lines of credit.

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

+ References

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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Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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

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No definition available.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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

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The average effective interest rate during the reporting period.

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

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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.

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No definition available.

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Face (par) amount of the original debt instrument that was repurchased.

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No definition available.

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Amount, after accumulated amortization, of debt discount (premium).

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Fixed interest rate related to the interest rate derivative.

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The number of derivative instruments of a particular group held by the entity.

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

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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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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Weighted average interest rate of long-term debt outstanding calculated at point in time.

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No definition available.

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The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Unsecured Debt - Narrative (Details)	1 Months Ended		3 Months Ended	12 Months Ended
Unsecured Debt - Narrative (Details)	Jan. 31, 2018 USD ($) extension	Apr. 30, 2013 USD ($)	Sep. 30, 2012 USD ($)	Dec. 31, 2017 USD ($) extension line_of_credit instrument	Dec. 31, 2016 USD ($)	Apr. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Nov. 30, 2016 USD ($)	Oct. 31, 2016 USD ($)	Apr. 30, 2016	Mar. 31, 2015 USD ($)	Apr. 30, 2014 USD ($)	Apr. 01, 2014 USD ($)
Debt Instrument [Line Items]
Unamortized debt issuance expense				$ 5,400,000	$ 7,400,000
Number of outstanding lines of credit \| line_of_credit				2
Senior notes				$ 275,000,000	$ 315,000,000
Effective interest rate				4.50%	4.50%
Unsecured debt, net				$ 3,501,709,000	$ 3,246,779,000
Debt instrument, face amount				2,900,000,000	2,850,000,000
Lines of credit				179,000,000	125,000,000
Unsecured Line of Credit [Member]
Debt Instrument [Line Items]
Lines of credit				179,000,000
Unsecured Bonds 3.625% [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				350,000,000	0
Unsecured Bonds 3.375%, Due April 2026 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				450,000,000	450,000,000
Unsecured Bonds 5.500% [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				0	300,000,000
Unsecured Bonds 5.200% [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				300,000,000	300,000,000
Unsecured Bonds 3.375% [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				300,000,000	300,000,000
Unsecured Bonds 3.875% [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				400,000,000	400,000,000
Unsecured Bonds 3.25% [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				300,000,000	300,000,000
Unsecured Bonds 3.625% [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				300,000,000	300,000,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, unamortized premium				5,200,000	100,000
Unamortized debt issuance expense				18,100,000	18,100,000
Unsecured Debt [Member] \| Senior Unsecured Notes Maturing April 1, 2025 [Member]
Debt Instrument [Line Items]
Senior notes				495,900,000	495,400,000
Debt instrument, face amount											$ 500,000,000
Interest rate, stated percentage											3.50%
Debt offering price											99.747%
Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity				1,030,000,000
Line of Credit [Member] \| Unsecured Line of Credit [Member]
Debt Instrument [Line Items]
Unamortized debt issuance expense				3,200,000	3,300,000
Lines of credit				$ 179,000,000	$ 125,000,000
Unsecured Line of Credit [Member]
Debt Instrument [Line Items]
Weighted average interest rate				2.30%	1.80%
Lines of credit				$ 179,000,000	$ 125,000,000
Unsecured Line of Credit [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 1,000,000,000
Number of extension options \| extension				1
Term extension period				18 months
Unsecured Line of Credit [Member] \| Line of Credit [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 1,200,000,000
Number of extension options \| extension	1
Term extension period	18 months
Unsecured Line of Credit [Member] \| Line of Credit [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on rate				0.90%
Unsecured Line of Credit [Member] \| Line of Credit [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on rate	0.875%
Unsecured Line of Credit [Member] \| Line of Credit Working Capital [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 25,000,000
Lines of credit				$ 0	0
Unsecured Line of Credit [Member] \| Line of Credit Working Capital [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 35,000,000
Unsecured Line of Credit [Member] \| Line of Credit Working Capital [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on rate				0.90%
Variable rate term loan [Member]
Debt Instrument [Line Items]
Unsecured debt, net					$ 100,000,000			$ 350,000,000	$ 225,000,000
Weighted average interest rate				2.50%	2.30%
Derivative, notional amount				$ 175,000,000
Basis spread on rate				0.95%
Variable rate term loan [Member] \| Carrying Value [Member]
Debt Instrument [Line Items]
Unsecured debt, net				$ 348,545,000	$ 98,189,000
Variable rate term loan [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Unsecured debt, net				$ 350,000,000
Number of derivative instruments held \| instrument				5
Term of loan				5 years
Variable rate term loan [Member] \| Variable Term Loan, Tranche One [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Derivative, notional amount				$ 175,000,000
Derivative, fixed interest rate				2.30%
Senior Notes [Member] \| BRE Properties, Inc. [Member]
Debt Instrument [Line Items]
Unsecured debt, net				$ 603,200,000	907,100,000
Long-term debt acquired													$ 900,000,000
Senior Notes [Member] \| Unsecured Bonds 3.625% [Member]
Debt Instrument [Line Items]
Unsecured debt, net				$ 345,200,000
Debt instrument, face amount						$ 350,000,000
Interest rate, stated percentage				3.625%
Debt offering price						99.423%
Senior Notes [Member] \| Unsecured Bonds 3.375%, Due April 2026 [Member]
Debt Instrument [Line Items]
Unsecured debt, net				$ 444,400,000	443,700,000
Interest rate, stated percentage				3.375%
Debt offering price										99.386%
Senior Notes [Member] \| Unsecured Bonds 5.500% [Member]
Debt Instrument [Line Items]
Interest rate, stated percentage				5.50%								5.50%
Face amount of debt paid off							$ 300,000,000
Senior Notes [Member] \| Unsecured Bonds 5.200% [Member]
Debt Instrument [Line Items]
Interest rate, stated percentage				5.20%
Senior Notes [Member] \| Unsecured Bonds 3.375% [Member]
Debt Instrument [Line Items]
Interest rate, stated percentage				3.375%
Senior Notes [Member] \| Unsecured Bonds 3.875% [Member]
Debt Instrument [Line Items]
Unsecured debt, net				$ 395,800,000	395,100,000
Debt instrument, face amount												$ 400,000,000
Interest rate, stated percentage				3.875%								3.875%
Debt offering price												99.234%
Senior Notes [Member] \| Unsecured Bonds 3.25% [Member]
Debt Instrument [Line Items]
Interest rate, stated percentage		3.25%		3.25%
Debt offering price		99.152%
Proceeds from issuance of unsecured debt		$ 300,000,000
Long-term debt, gross				$ 297,000,000	296,500,000
Senior Notes [Member] \| Unsecured Bonds 3.625% [Member]
Debt Instrument [Line Items]
Interest rate, stated percentage			3.625%	3.625%
Debt offering price			98.99%
Proceeds from issuance of unsecured debt			$ 300,000,000
Long-term debt, gross				$ 297,200,000	$ 296,600,000