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Real Estate and Accumulated Depreciation - Additional Information (Detail) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
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SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract] |  |
Real estate investments for federal income tax | $ 1,550 | $ 1,330

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- Definition Cost basis of real estate investments for federal income tax purposes for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Footnote 6 -Subsection 28 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 970 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Footnote 6)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
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