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Fair Value Disclosure of Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 30, 2016 | Dec. 31, 2015
Fixed Rate Debt |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Notes Payable, fair value | $ 2,760.0 | $ 2,710.0
Notes Payable Excluding Interest Rate Swaps and Cap Agreements | 2,570.0 | 2,610.0
Variable Rate Debt |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Notes Payable, fair value | 910.0 | 817.7
Notes Payable Excluding Interest Rate Swaps and Cap Agreements | $ 920.0 | $ 815.0
Minimum [Member] | Conventional Variable Rate Debt [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt Renewal Period | 30 days |
Maximum [Member] | Conventional Variable Rate Debt [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Debt Renewal Period | 90 days |

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- Definition Notes Payable Excluding Interest Rate Swaps and Cap Agreements + References No definition available. + Details
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- 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
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- Definition Fair value portion of notes payable. + 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 210.5-02.19,20,22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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