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Derivative Instruments and Hedging Activities (Details) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Nov. 30, 2016 USD ($) instrument | Dec. 31, 2016 USD ($) instrument | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($)
Derivative [Line Items] |  |  |  |
Unsecured debt, net |  | $ 3,246,779,000 | $ 3,088,680,000 |
Total return swap income |  | 11,716,000 | 5,655,000 | $ 0
Variable rate term loan [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Unsecured debt, net | $ 350,000,000 | $ 100,000,000 | 225,000,000 |
Debt instrument, term | 5 years |  |  |
Basis spread on rate (in hundredths) |  | 0.95% |  |
Derivative, notional amount | $ 200,000,000.0 |  | 225,000,000 |
Multifamily Housing Mortgage Revenue Bonds [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Bond subject to interest rate caps |  | $ 257,300,000 |  |
Interest Rate Swap [Member] | Variable rate term loan [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Unsecured debt, net |  | $ 100,000,000 |  |
Number of derivative instruments held | instrument |  | 4 |  |
Total Return Swap [Member] | Multifamily Housing Mortgage Revenue Bonds [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Bond subject to interest rate caps |  | $ 20,700,000 |  |
Designated as Hedging Instrument [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Hedge ineffectiveness related to cash flow hedges |  | 300,000 | 0 | $ 0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Number of derivative instruments held | instrument | 4 |  |  |
Derivative, notional amount |  | $ 150,000,000.0 |  |
Average fixed interest rate (as a percent) |  | 2.20% |  |
Derivative, fair value |  | $ 4,400,000 | 0 |
Aggregate carrying value of the interest rate swap contracts |  | 33,100 | 1,000,000 |
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Variable rate term loan [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Derivative, notional amount |  | 25,000,000.0 |  |
Not Designated as Hedging Instrument [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Total return swap income |  | 11,700,000 | 5,700,000 |
Not Designated as Hedging Instrument [Member] | Interest Rate Cap [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Derivative, notional amount |  | 20,700,000.0 |  |
Derivative, fair value |  | $ 0 | 0 |
Not Designated as Hedging Instrument [Member] | Total Return Swap [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Number of derivative instruments held | instrument |  | 4 |  |
Derivative, fair value |  | $ 0 | $ 4,000 |
Not Designated as Hedging Instrument [Member] | Total Return Swap [Member] | Multifamily Housing Mortgage Revenue Bonds [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Bond subject to interest rate caps |  | $ 257,300,000 |  |
Not Designated as Hedging Instrument [Member] | Total Return Swap [Callable] |  |  |  |
Derivative [Line Items] |  |  |  |
Number of derivative instruments held | instrument |  | 1 |  |
Derivative, notional amount |  | $ 114,400,000 |  |
Not Designated as Hedging Instrument [Member] | Total Return Swap, Jan 1, 2017 [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Number of derivative instruments held | instrument |  | 3 |  |
Derivative, notional amount |  | $ 142,900,000 |  |

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- Definition 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 + Details
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- Definition Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=64830801&loc=SL51823488-111719 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624163-113959 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226000-175313 + Details
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- Definition The loss recognized in earnings during the reporting period representing the amount of the cash flow hedges' ineffectiveness. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959 + Details
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