Apartment Income REIT Corp - Ordinary Shares (AIRC) 10-K 15 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Mar. 05, 2021	Dec. 15, 2020
Document Information [Line Items]
Entity Registrant Name	APARTMENT INCOME REIT CORP.
Entity Central Index Key	0001820877
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Trading Symbol	AIRC
Entity File Number	1-39686
Entity Tax Identification Number	84-1299717
Entity Incorporation, State or Country Code	MD
Entity Address, Address Line One	4582 South Ulster Street
Entity Address, Address Line Two	Suite 1700
Entity Address, City or Town	Denver
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80237
City Area Code	303
Local Phone Number	757-8101
Entity Common Stock, Shares Outstanding		148,985,740
Title of 12(b) Security	Class A Common Stock (Apartment Income REIT Corp.)
Security Exchange Name	NYSE
Document Annual Report	true
Document Transition Report	false
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 5.6
ICFR Auditor Attestation Flag	true
Documents Incorporated by Reference	Portions of Part III will be incorporated by reference in accordance with Instruction G(3) to Form 10-K no later than 120 days after the end of the registrant’s fiscal year.
AIMCO Properties, LP [Member]
Document Information [Line Items]
Entity Registrant Name	AIMCO PROPERTIES, L.P.
Entity Central Index Key	0000926660
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity File Number	0-24497
Entity Tax Identification Number	84-1275621
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	4582 South Ulster Street
Entity Address, Address Line Two	Suite 1700
Entity Address, City or Town	Denver
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80237
City Area Code	303
Local Phone Number	757-8101
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
ICFR Auditor Attestation Flag	true

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Buildings and improvements	$ 6,127,249	$ 5,930,910
Land	1,341,615	1,421,069
Total real estate	7,468,864	7,351,979
Accumulated depreciation	(2,455,505)	(2,268,839)
Net real estate	5,013,359	5,083,140
Cash and cash equivalents	44,214	136,458
Restricted cash	29,266	30,083
Notes receivable from Aimco	534,127	0
Goodwill	32,286	32,286
Other assets	576,026	604,593
Assets of discontinued operations	0	1,022,696
Total assets	6,229,278	6,909,256
LIABILITIES AND EQUITY
Non-recourse property debt, net	3,628,236	3,737,805
Term loan, net	349,164	0
Revolving credit facility borrowings	265,600	275,000
Total indebtedness	4,243,000	4,012,805
Accrued liabilities and other	598,736	270,487
Liabilities of discontinued operations	0	663,389
Total liabilities	4,841,736	4,946,681
Preferred noncontrolling interests in AIR Operating Partnership	79,449	97,064
Redeemable noncontrolling interests in consolidated real estate partnership	0	4,716
Commitments and contingencies (Note 7)
Equity/Partners' Capital:
Perpetual preferred stock	2,000	0
Common Stock, $0.01 par value, 1,021,175,000 and 500,787,260 shares authorized at December 31, 2020 and 2019, respectively, and 148,861,036 and 120,242,385 shares issued/outstanding at December 31, 2020 and 2019, respectively	1,489	1,202
Additional paid-in capital	3,432,121	3,497,654
Accumulated other comprehensive income	3,039	4,195
Distributions in excess of earnings	(2,131,798)	(1,722,402)
Total AIR equity	1,306,851	1,780,649
Noncontrolling interests in consolidated real estate partnerships	(61,943)	(3,296)
Common noncontrolling interests in AIR Operating Partnership	63,185	83,442
Total equity	1,308,093	1,860,795
Total liabilities and equity	6,229,278	6,909,256
AIMCO Properties, LP [Member]
ASSETS
Buildings and improvements	6,127,249	5,930,910
Land	1,341,615	1,421,069
Total real estate	7,468,864	7,351,979
Accumulated depreciation	(2,455,505)	(2,268,839)
Net real estate	5,013,359	5,083,140
Cash and cash equivalents	44,214	136,458
Restricted cash	29,266	30,083
Goodwill	32,286	32,286
Other assets	576,026	604,593
Total assets	6,229,278	6,909,256
Notes receivable from Aimco	534,127
Assets of discontinued operations		1,022,696
LIABILITIES AND EQUITY
Non-recourse property debt, net	3,628,236	3,737,805
Term loan, net	349,164
Revolving credit facility borrowings	265,600	275,000
Total indebtedness	4,243,000	4,012,805
Accrued liabilities and other	598,736	270,487
Total liabilities	4,841,736	4,946,681
Preferred noncontrolling interests in AIR Operating Partnership	79,449	97,064
Redeemable noncontrolling interests in consolidated real estate partnership		4,716
Commitments and contingencies (Note 7)
Equity/Partners' Capital:
Preferred units	2,000
General Partner and Special Limited Partner	1,304,851	1,780,649
Limited Partners	63,185	83,442
Partners’ capital attributable to the AIR Operating Partnership	1,370,036	1,864,091
Partners' Capital Attributable to Noncontrolling Interest	(61,943)	(3,296)
Total partners’ capital	1,308,093	1,860,795
Total liabilities and equity	$ 6,229,278	6,909,256
Liabilities of discontinued operations		$ 663,389

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized (in shares)	1,021,175,000	500,787,260
Common Stock, shares issued (in shares)	148,861,036	120,242,385
Common Stock, shares outstanding (in shares)	148,861,036	120,242,385

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
REVENUES:
Total revenues	$ 719,556	$ 770,602	$ 840,247
OPERATING EXPENSES:
Depreciation and amortization	320,943	317,283	329,394
General and administrative expenses	46,377	49,615	49,636
Provision for real estate impairment loss	47,281	0	0
Other expenses (income), net	73,860	16,737	(574)
Total operating expenses	737,497	644,876	664,101
Interest income	12,374	9,300	9,326
Interest expense	(160,359)	(150,888)	(179,805)
Gain on dispositions of real estate and the Asset Management business	119,215	503,168	677,463
Mezzanine / Unconsolidated partnerships investment income, net	27,576	1,531	0
Loss from unconsolidated real estate partnerships	0	0	(864)
(Loss) income from continuing operations before income tax (expense) benefit and discontinued operations	(19,135)	488,837	682,266
Income tax (expense) benefit (Note 11)	(95,437)	(305)	13,346
(Loss) income from continuing operations	(114,572)	488,532	695,612
Income from discontinued operations, net of tax	11,228	19,495	20,991
Net (loss) income	(103,344)	508,027	716,603
Noncontrolling interests:
Net loss (income) attributable to noncontrolling interests in consolidated real estate partnerships	798	(187)	(8,220)
Net income attributable to preferred noncontrolling interests in AIR Operating Partnership	(7,019)	(7,708)	(7,739)
Net loss (income) attributable to common noncontrolling interests in AIR Operating Partnership	5,438	(26,049)	(34,417)
Net income attributable to noncontrolling interests	783	33,944	50,376
Net (loss) income attributable to AIR	(104,127)	474,083	666,227
Net income attributable to AIR preferred stockholders	0	(7,335)	(8,593)
Net income attributable to participating securities	(202)	(604)	(1,037)
Net (loss) income attributable to AIR common stockholders	$ (104,329)	$ 466,144	$ 656,597
(Loss) earnings per common share – basic
(Loss) income from continuing operations attributable to AIR per common share	$ (0.94)	$ 3.75	$ 5.21
Income from discontinued operations attributable to AIR per common share	0.09	0.16	0.17
Net (loss) income attributable to AIR per common share – basic	(0.85)	3.91	5.38
(Loss) earnings per common share – diluted
(Loss) income from continuing operations attributable to AIR per common share	(0.94)	3.74	5.20
Income from discontinued operations attributable to AIR per common share	0.09	0.16	0.17
Net (loss) income attributable to AIR per common share – diluted	$ (0.85)	$ 3.90	$ 5.37
Weighted average common shares/units outstanding - basic	122,446	119,307	122,097
Weighted average common shares/units outstanding - diluted	122,446	119,533	122,243
Net loss (income) attributable to noncontrolling interests in consolidated real estate partnerships	$ 798	$ (187)	$ (8,220)
AIMCO Properties, LP [Member]
REVENUES:
Total revenues	719,556	770,602	840,247
OPERATING EXPENSES:
Depreciation and amortization	320,943	317,283	329,394
General and administrative expenses	46,377	49,615	49,636
Provision for real estate impairment loss	47,281	0	0
Other expenses (income), net	73,860	16,737	(574)
Total operating expenses	737,497	644,876	664,101
Interest income	12,374	9,300	9,326
Interest expense	(160,359)	(150,888)	(179,805)
Gain on dispositions of real estate and the Asset Management business	119,215	503,168	677,463
Mezzanine / Unconsolidated partnerships investment income, net	27,576	1,531	0
Loss from unconsolidated real estate partnerships	0	0	(864)
(Loss) income from continuing operations before income tax (expense) benefit and discontinued operations	(19,135)	488,837	682,266
Income tax (expense) benefit (Note 11)	(95,437)	(305)	13,346
Income from discontinued operations, net of tax	11,228	19,495	20,991
Net (loss) income	(103,344)	508,027	716,603
Noncontrolling interests:
Net loss (income) attributable to noncontrolling interests in consolidated real estate partnerships	798	(187)	(8,220)
Net (loss) income attributable to AIR	(102,546)	507,840	708,383
Net income attributable to AIR preferred stockholders	(7,019)	(15,043)	(16,332)
Net income attributable to participating securities	(202)	(620)	(1,177)
Net (loss) income attributable to AIR common stockholders	$ (109,767)	$ 492,177	$ 690,874
(Loss) earnings per common share – basic
(Loss) income from continuing operations attributable to AIR per common share	$ (0.94)	$ 3.75	$ 5.22
Income from discontinued operations attributable to AIR per common share	0.09	0.16	0.16
Net (loss) income attributable to AIR per common share – basic	(0.85)	3.91	5.38
(Loss) earnings per common share – diluted
(Loss) income from continuing operations attributable to AIR per common share	(0.94)	3.74	5.22
Net (loss) income attributable to AIR per common share – diluted	(0.85)	3.90	5.38
Income from discontinued operations attributable to the AIR Operating Partnership per common unit	$ 0.09	$ 0.16	$ 0.16
Weighted average common shares/units outstanding - basic	128,775	125,893	128,323
Weighted average common shares/units outstanding - diluted	128,775	126,164	128,469
(Loss) income from continuing operations	$ (114,572)	$ 488,532	$ 695,612
Net loss (income) attributable to noncontrolling interests in consolidated real estate partnerships	798	(187)	(8,220)
Rental and Other Property Revenues [Member]
REVENUES:
Total revenues	719,556	770,602	790,430
OPERATING EXPENSES:
Property operating expenses	249,036	261,241	264,724
Asset Management Business [Member]
REVENUES:
Total revenues	0	0	49,817
OPERATING EXPENSES:
Property operating expenses	0	0	20,921
Asset Management Business [Member] | AIMCO Properties, LP [Member]
REVENUES:
Total revenues	0	0	49,817
OPERATING EXPENSES:
Property operating expenses	0	0	20,921
Real Estate | AIMCO Properties, LP [Member]
REVENUES:
Total revenues	719,556	770,602	790,430
OPERATING EXPENSES:
Property operating expenses	$ 249,036	$ 261,241	$ 264,724

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net (loss) income	$ (103,344)	$ 508,027	$ 716,603
Other comprehensive (loss) gain:
Unrealized losses on available for sale debt securities	(1,236)	(637)	(131)
Losses on interest rate swaps reclassified into earnings from accumulated other comprehensive income	0	0	1,391
Other comprehensive (loss) gain	(1,236)	(637)	1,260
Comprehensive (loss) income	(104,580)	507,390	717,863
Comprehensive loss (income) attributable to noncontrolling interests	(703)	(33,906)	(50,445)
Comprehensive (loss) income attributable to AIR	(105,283)	473,484	667,418
AIMCO Properties, LP [Member]
Net (loss) income	(103,344)	508,027	716,603
Other comprehensive (loss) gain:
Unrealized losses on available for sale debt securities	(1,236)	(637)	(131)
Losses on interest rate swaps reclassified into earnings from accumulated other comprehensive income			1,391
Other comprehensive (loss) gain	(1,236)	(637)	1,260
Comprehensive (loss) income	(104,580)	507,390	717,863
Comprehensive loss (income) attributable to noncontrolling interests	798	(187)	(8,220)
Comprehensive (loss) income attributable to AIR	$ (103,782)	$ 507,203	$ 709,643

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Distributions in Excess of Earnings	Distributions in Excess of EarningsCumulative Effect, Period of Adoption, Adjustment	Total AIR's Predecessor	Total AIR's PredecessorCumulative Effect, Period of Adoption, Adjustment	Noncontrolling Interest in Consolidated Real Estate Partnerships	Common Noncontrolling Interests In AIR Operating Partnerships
Balances at Dec. 31, 2017	$ 1,655,753		$ 125,000	$ 1,231	$ 3,900,383	$ 3,603	$ (2,367,073)		$ 1,663,144		$ (1,716)	$ (5,675)
Balances (in shares) at Dec. 31, 2017			5,000	123,109
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchases of Common Stock	(373,592)			$ (64)	(373,528)				(373,592)
Repurchases of Common Stock (in shares)				(6,437)
Issuance of Aimco Operating Partnership units	50,151											50,151
Redemption of Aimco Operating Partnership units	(9,639)								0		0	(9,639)
Amortization of share-based compensation cost	9,765				8,074				8,074			1,691
Amortization of share-based compensation cost (in shares)				17
Effect of changes in ownership for consolidated entities	(10,101)				(19,115)				(19,115)			9,014
Change in accumulated other comprehensive income	1,260					1,191			1,191			69
Net income	708,864						666,227		666,227		8,220	34,417
Distributions to noncontrolling interests	(22,310)										(9,471)	(12,839)
Common Stock dividends	(238,067)						(238,067)		(238,067)
Preferred Stock dividends	(8,594)						(8,594)		(8,594)
Other, net	151			$ 1	150		0		151
Other, net (in shares)				111
Balances at Dec. 31, 2018	1,763,641		$ 125,000	$ 1,168	3,515,964	4,794	(1,947,507)		1,699,419		(2,967)	67,189
Balances (in shares) at Dec. 31, 2018			5,000	116,800
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchases of Common Stock	(20,682)			$ (4)	(20,678)				(20,682)
Repurchases of Common Stock (in shares)			0	(372)
Redemption of Preferred Stock	(125,000)		$ (125,000)		4,089		(4,089)		(125,000)
Redemption of Preferred Stock (in shares)			(5,000)
Issuance of Aimco Operating Partnership units	3,034											3,034
Redemption of Aimco Operating Partnership units	(6,467)			$ 1	6,242				6,243		0	(12,710)
Redemption of Aimco Operating Partnership units (in shares)				103
Amortization of share-based compensation cost	9,108				5,924				5,924			3,184
Amortization of share-based compensation cost (in shares)				18
Effect of changes in ownership for consolidated entities	0				(13,243)				(13,243)		3,422	9,821
Purchase of noncontrolling interests in consolidated real estate partnerships	(3,844)										(3,844)
Change in accumulated other comprehensive income	(637)					(599)			(599)			(38)
Net income	500,514						474,083		474,083		382	26,049
Distributions to noncontrolling interests	(13,395)										(308)	(13,087)
Common Stock dividends	(241,643)						(241,643)		(241,643)
Common Stock issued to Common Stockholders in special dividend	(740)			$ 36	(776)				(740)
Common Stock issued to Common Stockholders in special dividend (in shares)				3,628
Preferred Stock dividends	(3,246)						(3,246)		(3,246)
Other, net	152			$ 1	132		0		133		19
Other, net (in shares)				65
Balances at Dec. 31, 2019	1,860,795		$ 0	$ 1,202	3,497,654	4,195	(1,722,402)		1,780,649		(3,296)	83,442
Balances (in shares) at Dec. 31, 2019			0	120,242
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of Preferred Stock (in shares)			5,000
Repurchases of Common Stock	(10,004)			$ (2)	(10,002)				(10,004)
Repurchases of Common Stock (in shares)			0	(189)
Issuance of Preferred Stock	2,000		$ 2,000						2,000
Issuance of Preferred Stock, Shares			20
Redemption of Aimco Operating Partnership units	(2,642)			$ 3	5,136				5,139		0	(7,781)
Redemption of Aimco Operating Partnership units (in shares)				128
Amortization of share-based compensation cost	9,241				4,900				4,900			4,341
Amortization of share-based compensation cost (in shares)				20
Effect of changes in ownership for consolidated entities	438,470				494,589				494,589		(61,320)	5,201
Contribution from noncontrolling interest in consolidated realestate partnerships	4,701										4,701
Change in accumulated other comprehensive income	(1,236)					(1,156)			(1,156)			(80)
Net income	(109,944)						(104,127)		(104,127)		(379)	(5,438)
Distributions to noncontrolling interests	(18,182)										(1,682)	(16,500)
Common Stock dividends	(304,992)						(304,992)		(304,992)
Common Stock issued to Common Stockholders in special dividend				$ 286	(286)
Common Stock issued to Common Stockholders in special dividend (in shares)				28,629
Distributions to Aimco for the business separation	(559,856)				(559,753)				(559,753)		(103)
Other, net	19				(117)		0		(117)		136
Other, net (in shares)				31
Balances at Dec. 31, 2020	$ 1,308,093	$ (277)	$ 2,000	$ 1,489	$ 3,432,121	$ 3,039	$ (2,131,798)	$ (277)	$ 1,306,851	$ (277)	$ (61,943)	$ 63,185
Balances (in shares) at Dec. 31, 2020			20	148,861

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	$ (103,344)	$ 508,027	$ 716,603
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	320,943	317,283	329,394
Provision for real estate impairment loss	47,281	0	0
Gain on dispositions of real estate and the Asset Management business	(119,215)	(503,168)	(677,463)
Income tax expense (benefit)	95,437	305	(13,346)
Share-based compensation expense	8,295	8,146	8,550
Amortization of debt issuance costs and other	7,954	7,110	8,215
Other, net	(1,102)	0	1,046
Changes in operating assets and operating liabilities:
Accounts receivable and other assets	(57,881)	(26,021)	(27,830)
Accounts payable, accrued liabilities and other	12,672	2,798	1,681
Total adjustments	379,993	(133,556)	(320,215)
Net cash provided by operating activities	276,649	374,471	396,388
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of real estate and deposits related to purchases of real estate	(4,353)	(42,216)	(242,297)
Capital expenditures	(346,914)	(354,690)	(302,803)
Proceeds from dispositions of real estate and the Asset Management Business	159,422	628,771	708,848
Payment for mezzanine investment and related transaction costs	0	(277,627)	0
Purchases of corporate assets	(17,328)	(17,584)	(7,718)
Other investing activities	(29,326)	(7,201)	3,502
Net cash (used in) provided by investing activities	(349,999)	(205,413)	121,846
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from non-recourse property debt of continuing operations	643,756	712,143	1,134,747
Principal repayments on non-recourse property debt of continuing operations	(772,935)	(462,152)	(858,078)
Proceeds from (repayments of) term loan	350,000	0	(250,000)
Net (repayments of) borrowings on revolving credit facility	(9,400)	114,640	93,200
Payment of debt issuance costs	(6,607)	(4,861)	(11,961)
Payment of debt extinguishment costs	(14,831)	(4,491)	(14,241)
Cash distributed to Aimco in Separation	(257,296)	0	0
Repurchases of Common Stock	(10,004)	(20,682)	(373,592)
Repurchases of Preferred Stock	0	(125,000)	0
Payment of dividends to holders of Preferred Stock	0	(3,246)	(8,594)
Payment of dividends to holders of Common Stock	(304,992)	(241,288)	(237,504)
Payment of distributions to noncontrolling interests	(25,474)	(21,620)	(29,196)
Redemptions of noncontrolling interests in the AIR Operating Partnership	(20,259)	(10,694)	(9,885)
Contribution from noncontrolling interests in consolidated real estate partnerships	456,675	4,911	0
Purchases of noncontrolling interests in consolidated real estate partnerships	0	(3,780)	(3,579)
Other financing activities	(10,477)	(2,437)	5,233
Net cash used in financing activities	(26,037)	(63,952)	(588,179)
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	(99,387)	105,106	(69,945)
NET DECREASE (INCREASE) IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH OF DISCONTINUED OPERATIONS	6,326	(6,356)	281
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH OF CONTINUING OPERATIONS	(93,061)	98,750	(69,664)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH AT BEGINNING OF PERIOD	166,541	67,791	137,455
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH AT END OF PERIOD	73,480	166,541	67,791
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid, net of amounts capitalized	145,000	160,961	199,996
Cash paid for income taxes	12,168	12,238	11,522
Non-recourse property debt assumed in connection with the acquisition of real estate	0	97,565	208,885
Deferred tax liability assumed in connection with the acquisition of real estate	0	148,809	0
Issuance of common OP Units in connection with acquisition of real estate	0	3,034	50,151
Non-recourse property debt assumed by buyer in connection with the disposition of the Asset Management business	0	0	227,708
Assets, net of liabilities distributed to Aimco	559,753	0	0
Mezzanine investment liability	307,362	0	0
Other liabilities incurred in the Separation, net	5,506	0	0
Recognition of right of use lease assets	9,667	54,626	0
Recognition of lease liabilities	9,667	59,251	0
Accrued capital expenditures (at end of period)	31,323	54,358	40,185
Accrued dividends on TSR restricted stock and LTIP awards (at end of period) (Note 10)	1,327	1,420	1,266
AIMCO Properties, LP [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	(103,344)	508,027	716,603
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	320,943	317,283	329,394
Provision for real estate impairment loss	47,281	0	0
Gain on dispositions of real estate and the Asset Management business	(119,215)	(503,168)	(677,463)
Income tax expense (benefit)	95,437	305	(13,346)
Share-based compensation expense	8,295	8,146	8,550
Amortization of debt issuance costs and other	7,954	7,110	8,215
Other, net	(1,102)	0	1,046
Changes in operating assets and operating liabilities:
Accounts receivable and other assets	(57,881)	(26,021)	(27,830)
Accounts payable, accrued liabilities and other	12,672	2,798	1,681
Total adjustments	379,993	(133,556)	(320,215)
Net cash provided by operating activities	276,649	374,471	396,388
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of real estate and deposits related to purchases of real estate	(4,353)	(42,216)	(242,297)
Capital expenditures	(346,914)	(354,690)	(302,803)
Proceeds from dispositions of real estate and the Asset Management Business	159,422	628,771	708,848
Payment for mezzanine investment and related transaction costs	0	(277,627)	0
Purchases of corporate assets	(17,328)	(17,584)	(7,718)
Other investing activities	(29,326)	(7,201)	3,502
Net cash (used in) provided by investing activities	(349,999)	(205,413)	121,846
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from non-recourse property debt of continuing operations	643,756	712,143	1,134,747
Principal repayments on non-recourse property debt of continuing operations	(772,935)	(462,152)	(858,078)
Proceeds from (repayments of) term loan	350,000	0	(250,000)
Net (repayments of) borrowings on revolving credit facility	(9,400)	114,640	93,200
Payment of debt issuance costs	(6,607)	(4,861)	(11,961)
Payment of debt extinguishment costs	(14,831)	(4,491)	(14,241)
Cash distributed to Aimco in Separation	(257,296)	0	0
Repurchases of Common Stock	(10,004)	(20,682)	(373,592)
Redemption of preferred units from Aimco	0	(125,000)	0
Payment of dividends to holders of Preferred Stock	(7,019)	(10,954)	(16,334)
Payment of distributions General Partner and Special Limited Parter	(304,992)	(241,288)	(237,504)
Payment of distributions to Limited Partners	(16,667)	(13,399)	(11,987)
Payment of distributions to noncontrolling interests	(1,788)	(513)	(9,469)
Redemption of common and preferred units	(20,259)	(10,694)	(9,885)
Contribution from noncontrolling interests in consolidated real estate partnerships	456,675	4,911	0
Purchases of noncontrolling interests in consolidated real estate partnerships	0	(3,780)	(3,579)
Other financing activities	(10,477)	(2,437)	5,233
Net cash used in financing activities	(26,037)	(63,952)	(588,179)
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	(99,387)	105,106	(69,945)
NET DECREASE (INCREASE) IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH OF DISCONTINUED OPERATIONS	6,326	(6,356)	281
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH OF CONTINUING OPERATIONS	(93,061)	98,750	(69,664)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH AT BEGINNING OF PERIOD	166,541	67,791	137,455
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH AT END OF PERIOD	73,480	166,541	67,791
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid, net of amounts capitalized	145,000	160,961	199,996
Cash paid for income taxes	12,168	12,238	11,522
Non-recourse property debt assumed in connection with the acquisition of real estate	0	97,565	208,885
Deferred tax liability assumed in connection with the acquisition of real estate	0	148,809	0
Issuance of common OP Units in connection with acquisition of real estate	0	3,034	50,151
Non-recourse property debt assumed by buyer in connection with the disposition of the Asset Management business	0	0	227,708
Assets, net of liabilities distributed to Aimco	559,753	0	0
Mezzanine investment liability	307,362	0	0
Other liabilities incurred in the Separation, net	5,506	0	0
Recognition of right of use lease assets	9,667	54,626	0
Recognition of lease liabilities	9,667	59,251	0
Accrued capital expenditures (at end of period)	31,323	54,358	40,185
Accrued dividends on TSR restricted stock and LTIP awards (at end of period) (Note 10)	1,327	1,420	1,266
Discontinued Operations [Member]
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	72,729	62,887	48,392
Income tax expense (benefit)	(7,939)	(3,440)	319
Other, net	819	544	827
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of real estate and deposits related to purchases of real estate	(92,485)	(96,095)	0
Capital expenditures	(19,015)	(38,771)	(37,686)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from non-recourse property debt of continuing operations	0	62,480	93,280
Principal repayments on non-recourse property debt of continuing operations	(44,193)	(57,875)	(118,009)
Discontinued Operations [Member] | AIMCO Properties, LP [Member]
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	72,729	62,887	48,392
Income tax expense (benefit)	(7,939)	(3,440)	319
Other, net	819	544	827
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of real estate and deposits related to purchases of real estate	(92,485)	(96,095)	0
Capital expenditures	(19,015)	(38,771)	(37,686)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from non-recourse property debt of continuing operations	0	62,480	93,280
Principal repayments on non-recourse property debt of continuing operations	$ (44,193)	$ (57,875)	$ (118,009)

Consolidated Statements of Part

Consolidated Statements of Partners' Capital - USD ($) $ in Thousands	Total	AIMCO Properties, LP [Member]	AIMCO Properties, LP [Member]Cumulative Effect, Period of Adoption, Adjustment	AIMCO Properties, LP [Member]Preferred Units [Member]	AIMCO Properties, LP [Member]General Partner and Special Limited Partner [Member]	AIMCO Properties, LP [Member]General Partner and Special Limited Partner [Member]Cumulative Effect, Period of Adoption, Adjustment	AIMCO Properties, LP [Member]Limited Partners [Member]	AIMCO Properties, LP [Member]Partners Capital Attributable to the Partnership [Member]	AIMCO Properties, LP [Member]Partners Capital Attributable to the Partnership [Member]Cumulative Effect, Period of Adoption, Adjustment	AIMCO Properties, LP [Member]Noncontrolling Interests [Member]
Balances at Dec. 31, 2017		$ 1,655,753		$ 125,000	$ 1,538,144		$ (5,675)	$ 1,657,469		$ (1,716)
Increase (Decrease) in Partners' Capital [Roll Forward]
Repurchases of common partnership units held by AIR's Predecessor		(373,592)			(373,592)			(373,592)
Issuance of Aimco Operating Partnership units	$ 50,151	50,151					50,151	50,151
Redemption of common partnership units		(9,639)					(9,639)	(9,639)
Amortization of share-based compensation cost		9,765			8,074		1,691	9,765
Effect of changes in ownership for consolidated entities		(10,101)			(19,115)		9,014	(10,101)
Change in accumulated other comprehensive income	1,260	1,260			1,191		69	1,260
Net income	708,864	708,864			666,227		34,417	700,644		8,220
Distributions to noncontrolling interests	(22,310)	(22,310)					(12,839)	(12,839)		(9,471)
Distributions to common unitholders		(238,067)			(238,067)			(238,067)
Distributions to preferred unitholders		(8,594)			(8,594)			(8,594)
Other, net		151			151			151
Balances at Dec. 31, 2018		1,763,641		125,000	1,574,419		67,189	1,766,608		(2,967)
Increase (Decrease) in Partners' Capital [Roll Forward]
Repurchases of common partnership units held by AIR's Predecessor		(20,682)			(20,682)			(20,682)
Redemption of preferred units held by AIR’s Predecessor		(125,000)		(125,000)				(125,000)
Issuance of Aimco Operating Partnership units	3,034	3,034					3,034	3,034
Redemption of common partnership units		(6,467)			6,243		(12,710)	(6,467)
Amortization of share-based compensation cost		9,108			5,924		3,184	9,108
Effect of changes in ownership for consolidated entities					(13,243)		9,821	(3,422)		3,422
Purchase of noncontrolling interest in consolidated real estate partnerships		(3,844)								(3,844)
Change in accumulated other comprehensive income	(637)	(637)			(599)		(38)	(637)
Net income	500,514	500,514			474,083		26,049	500,132		382
Distributions to noncontrolling interests	(13,395)	(13,395)					(13,087)	(13,087)		(308)
Distributions to common unitholders		(241,643)			(241,643)			(241,643)
Common partnership units issued to common unitholders in special distribution		(740)			(740)			(740)
Distributions to preferred unitholders		(3,246)			(3,246)			(3,246)
Other, net		152			133			133		19
Balances at Dec. 31, 2019		1,860,795			1,780,649		83,442	1,864,091		(3,296)
Increase (Decrease) in Partners' Capital [Roll Forward]
Repurchases of common partnership units held by AIR's Predecessor		(10,004)			(10,004)			(10,004)
Issuance of Preferred Stock		2,000		2,000				2,000
Redemption of common partnership units		(2,642)			5,139		(7,781)	(2,642)
Amortization of share-based compensation cost		9,241			4,900		4,341	9,241
Effect of changes in ownership for consolidated entities		438,470			494,589		5,201	499,790		(61,320)
Contribution from noncontrolling interest in consolidated realestate partnerships	4,701	4,701								4,701
Change in accumulated other comprehensive income	(1,236)	(1,236)			(1,156)		(80)	(1,236)
Net income	(109,944)	(109,944)			(104,127)		(5,438)	(109,565)		(379)
Distributions to noncontrolling interests	$ (18,182)	(18,182)					(16,500)	(16,500)		(1,682)
Distributions to common unitholders		(304,992)			(304,992)			(304,992)
Distributions to Aimco for the business separation		(559,856)			(559,753)			(559,753)		(103)
Other, net		19			(117)			(117)		136
Balances at Dec. 31, 2020		$ 1,308,093	$ (277)	$ 2,000	$ 1,304,851	$ (277)	$ 63,185	$ 1,370,036	$ (277)	$ (61,943)

Organization

Organization	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	Note 1 — Basis of Presentation and Organization Basis of Presentation The accompanying consolidated financial statements include the accounts of Apartment Income REIT Corp. (“AIR”), AIMCO Properties L.P. (“AIR Operating Partnership”), and their consolidated subsidiaries. The AIR Operating Partnership’s consolidated financial statements include the accounts of the AIR Operating Partnership and its consolidated subsidiaries. All significant intercompany balances have been eliminated in consolidation. Except as the context otherwise requires, “we,” “our,” and “us” refer to AIR, the AIR Operating Partnership and their consolidated subsidiaries, collectively. The Separation On December 15, 2020, Apartment Investment and Management Company (“Aimco”) completed the previously announced separation of its business into two, separate and distinct, publicly traded companies, AIR and Aimco (the “Separation”). Notwithstanding the legal form of the Separation, for accounting and financial reporting purposes, Aimco is presented as being spun-off from AIR (as it relates to Aimco subsequent to the Separation, the “Spinnee”). This presentation is in accordance with generally accepted accounting principles in the U.S. (“GAAP”), and is due primarily to the relative significance of AIR’s business, as measured in terms of revenues, net income, assets, and other relevant indicators, as compared to Aimco before the Separation Therefore, AIR is considered the divesting entity and treated as the accounting spinnor, and Aimco is presented as the predecessor (“AIR’s Predecessor”) for AIR’s financial statements. Unless otherwise stated, financial results prior to the Separation on December 15, 2020 include the financial results of AIR’s predecessor. The financial results attributable to the apartment communities retained by Aimco in the Separation are presented as discontinued operations. Unless otherwise noted, all disclosures in the notes accompanying the consolidated financial statements reflect only continuing operations. Please refer to Note 4 for further details regarding our discontinued operations. Organization and Business AIR is a self-administered and self-managed real estate investment trust (“REIT”). AIR owns, through its wholly-owned subsidiaries, all of the common equity, the general partner interest, and special limited partner interest in AIR Operating Partnership, a Delaware limited partnership originally incorporated on May 16, 1994. AIR Operating Partnership conducts all of the business of AIR, which is focused on the ownership of stabilized multi-family properties located in top markets including eight important geographic concentrations: Boston; Philadelphia; Greater Washington, D.C.; Miami; Denver; the San Francisco Bay Area; Los Angeles; and San Diego. Interests in the AIR Operating Partnership that are held by limited partners other than AIR are referred to as OP Units. OP Units include common partnership units, which we refer to as common OP Units, as well as preferred partnership units, which we refer to as preferred OP Units. As of December 31, 2020, after elimination of units held by consolidated subsidiaries, the AIR Operating Partnership had 159,155,544 common OP Units outstanding. As of December 31, 2020, AIR owned 148,861,036 of the common OP Units of the AIR Operating Partnership and AIR had an equal number of shares of its Class A Common Stock outstanding, which we refer to as Common Stock. AIR’s ownership of the total common OP Units outstanding represents a 93.5% legal interest in the AIR Operating Partnership and a 94.9% economic interest. We own and operate a portfolio of apartment communities, diversified by both geography and price point, in 12 states and the District of Columbia. As of December 31, 2020, our portfolio included 99 apartment communities with 26,592 apartment homes in which we held an average ownership of approximately 94%. Any references to the number of apartment communities and homes, square footage, or occupancy percentage in these notes to our consolidated financial statements are unaudited.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Summary of Significant Accounting Policies	Note 2 — Summary of Significant Accounting Policies Principles of Consolidation We consolidate a variable interest entity (“VIE”), in which we are considered the primary beneficiary. The primary beneficiary is the entity that has (i) the power to direct the activities that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses of the VIE or the right to receive benefits from the VIE that could be significant to the VIE. As used herein, and except where the context otherwise requires, “partnership” refers to a limited partnership or a limited liability company and “partner” refers to a partner in a limited partnership or a member of a limited liability company. Noncontrolling Interests in the AIR Operating Partnership Noncontrolling interests in the AIR Operating Partnership consist of common OP Units and preferred OP Units and are reflected in AIR’s accompanying consolidated balance sheets as noncontrolling interests in AIR Operating Partnership. Holders of preferred OP Units participate in the AIR Operating Partnership’s income or loss only to the extent of their preferred distributions. Within AIR’s consolidated financial statements, after provision for preferred OP Unit distributions, the AIR Operating Partnership’s income or loss is allocated to the holders of common OP Units based on the weighted-average number of common OP Units (including those held by AIR) outstanding during the period. During the years ended December 31, 2020, 2019, and 2018, the holders of common OP Units had a weighted-average economic ownership interest in the AIR Operating Partnership of 5.07%, 5.20%, and 5.31%, respectively. Please refer to Note 9 for further information regarding the items comprising noncontrolling interests in the AIR Operating Partnership. Substantially all of the assets and liabilities of AIR are those of the AIR Operating Partnership. Noncontrolling Interests in Consolidated Real Estate Partnerships We generally report the unaffiliated partners’ interests in the net assets of our consolidated real estate partnerships as noncontrolling interests in consolidated real estate partnerships within consolidated equity and partners’ capital. If a real estate partnership includes redemption rights that are not within AIR and the AIR Operating Partnership’s control, the noncontrolling interest is included as temporary equity or temporary capital. If the redemption right is not currently redeemable but probable of being redeemable in the future, changes in redemption value are recognized each quarter with the change in value being reflected in additional paid-in-capital. The assets of real estate partnerships consolidated by the AIR Operating Partnership must first be used to settle the liabilities of such consolidated real estate partnerships. These consolidated real estate partnerships’ creditors do not have recourse to the general credit of the AIR Operating Partnership. Noncontrolling interests in consolidated real estate partnerships consist primarily of equity interests held by limited partners in consolidated real estate partnerships that have finite lives. We generally attribute to noncontrolling interests their share of income or loss of consolidated partnerships based on their proportionate interest in the results of operations of the partnerships, including their share of losses even if such attribution results in a deficit noncontrolling interest balance within our equity and partners’ capital accounts. The terms of the related partnership agreements generally require the partnerships to be liquidated following the sale of the underlying real estate. As the general partner in these partnerships, we ordinarily control the execution of real estate sales and other events that could lead to the liquidation, redemption or other settlement of noncontrolling interests. Changes in our ownership interest in consolidated real estate partnerships generally consist of our purchase of an additional interest in or the sale of our entire or partial interest in a consolidated real estate partnership. The effect on our equity and partners’ capital of our purchase of additional interests in consolidated real estate partnerships during the years ended December 31, 2020, 2019, and 2018, is shown in our consolidated statements of equity and partners’ capital. The effect on our equity and partners’ capital of sales of consolidated real estate or sales of our entire interest in consolidated real estate partnerships is reflected in our consolidated financial statements as gains or losses on dispositions of real estate and accordingly the effect on our equity and partners’ capital is reflected within the amount of net income allocated to us and to noncontrolling interests. Upon our deconsolidation of a real estate partnership following the sale of our partnership interests or liquidation of the partnership following sale of the related apartment community, we derecognize any remaining noncontrolling interest of the associated partnership previously recorded in our consolidated balance sheets. Investments in Unconsolidated Real Estate Partnerships We may own general and limited partner interests in partnerships that either directly, or through interests in other real estate partnerships, own apartment communities. We generally account for investments in real estate partnerships that we do not consolidate under the equity method. Under the equity method, we recognize our share of the earnings or losses of the entity for the periods presented, inclusive of our share of any impairments and disposition gains or losses recognized by and related to such entities, and we present such amounts within income from unconsolidated real estate partnerships in our consolidated statements of operations. Investments in unconsolidated real estate partnerships are reviewed for impairments whenever events or changes in circumstances indicate that the carrying amount of the investment may not be recoverable. An impairment loss is recorded when there is a decline in the fair value below the carrying value and we conclude such decline is other-than-temporary. An impairment loss is measured based on the excess of the carrying amount of an investment over its estimated fair value. We determine the fair value of investments in unconsolidated real estate partnerships using valuation techniques that consider the terms of the in-place leases, current market data for comparable leases, our experience in leasing similar communities, and current plans. We recognized no such impairments for any of the years ended December 31, 2020 , 2019 , and 2018 The excess of our cost of the acquired partnership interests over our share of the partners’ equity or deficit is generally ascribed to the fair values of land and buildings owned by the partnerships. We amortize the excess cost ascribed to the buildings over the related estimated useful lives. Such amortization is recorded as an adjustment of the amounts of earnings or losses we recognize from such unconsolidated real estate partnerships. We may also originate loans for real estate acquisitions or developments where we either expect, or have the opportunity, to participate in the residual profits from such projects. When the risks and rewards of these arrangements are similar to an equity investor or joint venture partner, we account for these arrangements as real estate investments using the equity method of accounting. We recognize as income changes in our share of net assets, adjusted for any basis differential, in mezzanine investment income, net, in our consolidated statements of operations. In connection with the Separation, Aimco was allocated economic ownership of the mezzanine loan investment and option to acquire a 30% equity interest in the partnership owning Parkmerced Apartments. Subsequent to the Separation, all risks and rewards of ownership are Aimco’s. As of December 31, 2020, the investment in Parkmerced is included in other assets in AIR’s consolidated balance sheets, as title has not been legally transferred. Since AIR has legally assigned all risks and rewards of ownership to Aimco, there is an equal, and offsetting liability included in accrued liabilities and other in AIR’s consolidated balance sheets. Accordingly, there is no net effect on AIR’s shareholders’ equity . Real Estate Acquisitions Upon the acquisition of real estate, we determine whether the purchase qualifies as an asset acquisition or, less frequently, meets the definition of an acquisition of a business. We generally recognize the acquisition of apartment communities or interests in partnerships that own communities at our cost, including the related transaction costs, as asset acquisitions. We allocate the cost of apartment communities acquired based on the relative fair value of the assets acquired and liabilities assumed. The fair value of these assets and liabilities is determined using valuation techniques that rely on Level 2 and Level 3 inputs within the fair value framework. We determine the fair value of tangible assets, such as land, buildings, furniture, fixtures and equipment using valuation techniques that consider comparable market transactions, replacement costs and other available information. We determine the fair value of identified intangible assets or liabilities, which typically relate to in-place leases, using valuation techniques that consider the terms of the in-place leases, current market data for comparable leases and our experience in leasing similar communities. The intangible assets or liabilities related to in-place leases are comprised of: (a) the value of the above- and below-market leases in-place, measured over the period, including probable lease renewals for below-market leases, that the leases are expected to remain in effect; (b) the estimated unamortized portion of avoided leasing commissions and other costs that Capital Additions We capitalize costs, including certain indirect costs, incurred in connection with our capital additions activities, including redevelopments, developments, other tangible apartment community improvements, and replacements of existing apartment community components. Included in these capitalized costs are payroll costs associated with time spent by our teammates in connection with capital additions activities at the apartment community level. We characterize as “indirect costs” an allocation of certain department costs, including payroll, at the area operations and corporate levels that clearly relate to capital additions activities. We also capitalize interest, property taxes, and insurance during periods in which construction projects are in progress. We begin capitalization of costs, including certain indirect costs, incurred in connection with our capital addition activities, upon commencement of activities necessary to ready apartment communities for their intended use. These activities include when apartment communities or apartment homes are undergoing physical construction, as well as when homes are held vacant in advance of planned construction, provided that other activities such as permitting, planning and design are in progress. We cease the capitalization of costs when the apartment communities are substantially complete and ready for their intended use, which is typically when construction has been substantially completed and apartment homes are available for occupancy. Costs, including ordinary repairs, maintenance, and resident turnover costs, are charged to property operating expense as incurred. For the years ended December 31, 2020, 2019, and 2018, we capitalized to buildings and improvements $13.7 million, $11.6 million, and $7.3 million of interest costs, respectively, and $33.0 million, $36.4 million, and $35.9 million of other direct and indirect costs, respectively. Gain or Loss on Dispositions For sales of real estate, we evaluate whether the disposition has a major effect on our operations and financial results and qualify as a strategic shift. If the disposition represents a strategic shift, it is classified as discontinued operations in our consolidated financial statements for all periods presented. If the disposition does not represent a strategic shift, it is presented in continuing operations in our consolidated financial statements. Gain or loss on real estate dispositions are recognized when we no longer hold a controlling financial interest in the real estate and sufficient consideration has been received. Upon disposition, the related assets and liabilities are derecognized, and the gain or loss on disposition is recognized as the difference between the carrying amount of those assets and liabilities and the value of consideration received. Impairment Real estate and other long-lived assets to be held and used are individually evaluated for impairment when conditions exist that may indicate the carrying amount of a long-lived asset may not be recoverable. Impairment indicators include significant fluctuations in rental and other property revenues less property operating expenses, occupancy changes, significant near-term lease expirations, current and historical cash flow losses, rental rates, and if applicable, a comparison of an asset’s carrying value to its gross asset value, a measure representative of the estimated fair value of an asset. Upon determination that an impairment has occurred, we recognize an impairment loss to the extent the carrying amount exceeds the estimated fair value of the community. During the fourth quarter of 2020, we evaluated the expected hold period of a real estate asset in our Other Real Estate reporting segment. We acquired the property in 2004 for $51 million. The initial purchase price allocated to land and building totaled $81 million, which included the recording of a below market lease liability and a mark-to-market adjustment associated with assumed debt. Based on an expected shortened hold period, we reduced the carrying value of the asset to its estimated fair value of December 31, 2020 and recognized a non-cash impairment loss on real estate of The measurement of the impairment loss is based on the fair value of the communities and incorporates various estimates and assumptions, the most significant being market rental rates, operating expense assumptions, and capitalization rate. We project future rental revenue growth rates using forecasted rates from third-party market research analytics. Property expense growth rates and capitalization rate are based on the apartment communities’ historical, current, and expected future operating results, existing operating expense assumptions, and operational strategies. These projections are adjusted to reflect current economic conditions and require considerable management judgement. Cash Equivalents We classify highly liquid investments with an original maturity of three months or less as cash equivalents. We maintain cash equivalents in financial institutions in excess of insured limits. We have not experienced any losses in these accounts in the past and believe that we are not exposed to significant credit risk because our accounts are deposited with major financial institutions. Restricted Cash Restricted cash includes capital replacement reserves, completion repair reserves, bond sinking fund amounts, real estate tax and insurance escrow accounts held by lenders and resident security deposits. Goodwill As of December 31, 2020 $32.3 Other Assets As of December 31, 2020 and 2019, other assets was comprised of the following amounts (in thousands): 2020 2019 Mezzanine investment $ 307,362 $ 280,258 Investments in securitization trust 100,151 94,251 Right of use lease assets 56,783 61,911 Intangible assets, net 4,438 5,716 Notes receivable, net 894 4,715 Software, equipment, and leasehold improvements 6,531 25,750 Accounts receivable, net 21,458 18,668 Prepaid expenses, real estate taxes and insurance 10,970 10,831 Deferred tax asset, net (Note 11) — 80,516 Deferred costs, deposits and other 67,439 21,977 Total other assets $ 576,026 $ 604,593 Investments in Securitization Trust that holds AIR Property Debt We hold investments in a securitization trust that primarily holds certain of our property debt. These investments were initially recognized at their purchase price and the discount to the face value is being accreted into interest income over the expected term of the securities. We have designated these investments as available for sale (“AFS”) debt securities, and we measure these investments at fair value with changes in their fair value, other than the changes attributed to the accretion described above, recognized as an adjustment of accumulated other comprehensive income or loss within equity and partners’ capital. Please refer to Note 13 for further information regarding these debt securities. Notes Receivable from Aimco In connection with the Separation, we acquired $534 million in notes receivable pledged by a subsidiary of the Spinnee that has an interest in a portfolio of assets. Our notes receivable is subordinate to the existing debt of $215.4 million as of December 31, 2020, on the portfolio of assets. The notes receivable mature on January 31, 2024, and bear interest at a rate of 5.2% per annum, payable quarterly on January 1, April 1, July 1, and October 1, commencing on April 1, 2021. The notes receivable contain certain representations, warranties, covenants and events of default, and are secured by a pool of properties owned by Aimco. Notes receivable are reported in our consolidated balance sheet at the outstanding principal balance. Interest receivable related to the unpaid principal is recorded separately from the outstanding balance in other assets in our consolidated balance sheets. Deferred Costs We defer, as debt issuance costs, lender fees and other direct costs incurred in obtaining new financing and amortize the amounts over the terms of the related loan agreements. In connection with the modification of existing financing arrangements, we defer lender fees and amortize these costs and any unamortized debt issuance costs over the term of the modified loan agreement. Debt issuance costs associated with our revolving credit facility are included in other assets in our consolidated balance sheets. Debt issuance costs associated with non-recourse property debt and our term loan are presented as a direct deduction from the related liabilities in our consolidated balance sheets. When financing arrangements are repaid or otherwise extinguished prior to maturity, unamortized debt issuance costs are written off, additionally, any lender fees or other costs incurred in connection with the extinguishment are recognized as expense. Amortization and write-off of debt issuance costs and other extinguishment costs are included in interest expense in our consolidated statements of operations. We defer leasing costs incremental to a lease that we would not have incurred if the contract had not been obtained. Amortization of these costs is included in depreciation and amortization in our consolidated statements of operations. Revenue from Leases We are a lessor primarily for residential leases. Our operating leases with residents may also provide that the resident reimburse us for certain costs, primarily the resident’s share of utilities expenses, incurred by the apartment community. These reimbursements represent revenue attributable to nonlease components for which the timing and pattern of recognition is the same as the revenue for the lease components. In 2019, we adopted the practical expedient that allows us to account for the lease and nonlease components as a single component. Reimbursement and related expense are presented on a gross basis in our consolidated statements of operations, with the reimbursement included in rental and other property revenues attributable to real estate in our consolidated statements of operations. We recognize rental revenue attributed to lease components, net of any concessions, on a straight-line basis over the term of the lease. Asset Management Business Prior to the July 2018 sale of our Asset Management business, we provided asset management and other services to certain consolidated partnerships owning apartment communities that qualify for low-income housing tax credits and are structured to provide for the pass-through of tax credits and tax deductions to their partners. We consolidated those low-income housing tax credit partnerships in which we were the sole general partner and decision maker of the partnerships. We recognized income from asset management and other services when the related fees were earned and realized or realizable. Depreciation and Amortization Depreciation for all tangible assets is calculated using the straight-line method over their estimated useful lives. Acquired buildings and improvements are depreciated over a useful life based on the age, condition, and other physical characteristics of the asset. Furniture, fixtures, and equipment are generally depreciated over five years. We depreciate capitalized costs using the straight-line method over the estimated useful life of the related improvement, which is generally 5, 15, or 30 years. We also capitalize payroll and other indirect costs incurred in connection with preparing an asset for its intended used. These costs include corporate-level costs that clearly relate to the capital addition activities, which we allocate to the applicable assets. All capitalized payroll costs and indirect costs are allocated to capital additions proportionately based on direct costs and depreciated over the estimated useful lives of such capital additions. Purchased software and other costs related to software purchased or developed for internal use are capitalized during the application development stage and are amortized using the straight-line method over the estimated useful life of the software, generally three to five years. Purchased equipment is recognized at cost and depreciated using the straight-line method over the estimated useful life of the asset, which is generally five years. Leasehold improvements are also recorded at cost and depreciated on a straight-line basis over the shorter of the asset’s estimated useful life or the term of the related lease. Certain homogeneous items that are purchased in bulk on a recurring basis, such as appliances, are depreciated using group methods that reflect the average estimated useful life of the items in each group. Except in the case of apartment community casualties, where the net book value of the lost asset is written off in the determination of casualty gains or losses, we generally do not recognize any loss in connection with the replacement of an existing apartment community component because normal replacements are considered in determining the estimated useful lives used in connection with our composite and group depreciation methods. Insurance We believe our insurance coverages insure our apartment communities adequately against the risk of loss attributable to fire, earthquake, hurricane, tornado, flood, and other perils. In addition, we have third-party insurance coverage (after self-insured retentions) that defray the costs of large workers’ compensation, health, and general liability exposures. We accrue losses based upon our estimates of the aggregate liability for uninsured losses incurred using certain actuarial assumptions followed in the insurance industry and based on our experience. Share-Based Compensation We issue various forms of share-based compensation, including stock options and restricted stock awards with service conditions and/or market conditions. We recognize share-based employee compensation based on the fair value on the grant date and recognize compensation cost over the awards’ requisite service periods. We reduce compensation cost related to forfeited awards in the period of forfeiture. Please refer to Note 10 for further discussion of our share-based compensation. Income Taxes AIR has elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the “Code”), commencing with its taxable year ended December 31, 2020, and it intends to continue to operate in such a manner. AIR’s Predecessor also elected to be taxed as a REIT under the Code. AIR’s current and continuing qualification as a REIT depends on its ability to meet the various requirements imposed by the Internal Revenue Code, which are related to organizational structure, distribution levels, diversity of stock ownership and certain restrictions with regard to owned assets and categories of income. If AIR qualifies for taxation as a REIT, it will generally not be subject to United States federal corporate income tax on its taxable income that is currently distributed to stockholders. This treatment substantially eliminates the “double taxation” (at the corporate and stockholder levels) that generally results from an investment in a corporation. Even if AIR qualifies as a REIT, it may be subject to United States federal income and excise taxes in various situations, such as on undistributed income. AIR could also be subject to a 100% tax on transactions between it and a TRS (described below) that are determined to be non-arm’s length and on any net income from sales of apartment communities that are determined to be dealer-type prohibited transactions. The state and local tax laws may not conform to the United States federal income tax treatment, and AIR may be subject to state or local taxation in various state or local jurisdictions, including those in which we transact business. Any taxes imposed on us reduce our operating cash flow and net income. Certain of AIR’s operations, or a portion thereof, including property management and risk management, are conducted through taxable REIT subsidiaries, which are subsidiaries of the AIR Operating Partnership, and each of which we refer to as a TRS. A TRS is a subsidiary C-corporation that has not elected REIT status and, as such, is subject to United States federal corporate income tax. We use TRS entities to facilitate our ability to offer certain services and activities to our residents and investment partners that cannot be offered directly by a REIT. We also use TRS entities to hold investments in certain apartment communities. For our TRS entities, deferred income taxes result from temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for United States federal income tax purposes, and are measured using the enacted tax rates and laws that are expected to be in effect when the differences reverse. We reduce deferred tax assets by recording a valuation allowance when we determine, based on available evidence, that it is more likely than not that the assets will not be realized. We recognize the tax consequences associated with intercompany transfers between the AIR Operating Partnership and TRS entities when such transactions occur. Please refer to Note 11 for further information about our income taxes. Earnings per Share and Unit AIR and the AIR Operating Partnership calculate earnings per share and unit based on the weighted-average number of shares of Common Stock or common OP units, participating securities, common stock or common unit equivalents and dilutive convertible securities outstanding during the period. The AIR Operating Partnership considers both common OP units and equivalents, which have identical rights to distributions and undistributed earnings, to be common units for purposes of the earnings per unit computations. Please refer to Note 12 for further information regarding earnings per share and unit computations. Use of Estimates The preparation of our consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts included in the financial statements and accompanying notes thereto. Actual results could differ from those estimates. Reclassifications and Revisions On November 30, 2020, AIR’s Predecessor and the Aimco Operating Partnership effected a reverse split of Common Stock and common partnership units, respectively, at a ratio of one share or unit for every 1.23821 shares or units outstanding on the date of effectiveness. The accounting guidance for recapitalization events requires that we revise AIR’s equity and the AIR Operating Partnership’s partners’ capital as if the reverse split had occurred at the beginning of the earliest period presented. As such, we have revised the outstanding share and unit counts, presentation of share and unit activity, and earnings per share and unit, as if the reverse split had occurred on December 31, 2017. As previously stated in Note 1, the financial results prior to the Separation on December 15, 2020, include the financial results of AIR’s Predecessor, and the financial results attributable to the apartment communities retained by Aimco in the Separation are presented as discontinued operations. Accounting Pronouncements Adopted in the Current Year On January 1, 2020, we adopted ASC 326, Financial Instruments – Credit Losses Recent Accounting Pronouncements On January 16, 2020, the FASB issued an Accounting Standards Update that addresses accounting for the transition into and out of the equity method and provides clarification of the interaction of rules for equity securities, the equity method of accounting, and forward contracts and purchase options on certain types of securities, which is effective for us on January 1, 2021. Adoption of the standards requires changes to be made prospectively and early adoption is permitted. The adoption of this standard on January 1, 2021 did not result in a change in our accounting. On August 5, 2020, the FASB issued an Accounting Standards Update that simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, and affects the diluted earnings per share calculation for instruments that may be settled in cash or shares, which is effective for us on January 1, 2021. Adoption of the standards requires changes to be made retrospectively and early adoption is permit ted. Our preferred OP units are subject to the new standard, which will require us to include our preferred OP units in the calculation of dilutive securities. The adoption of this standard on January 1, 2021 , did not have an impact to our consolidated financial statements.

Significant Transactions

Significant Transactions	12 Months Ended
	Dec. 31, 2020
Significant Transactions [Abstract]
Significant Transactions	Note 3 — Significant Transactions Joint Venture Transaction On September 8, 2020, we formed a joint venture with a passive institutional investor to own a portfolio of 12 multi-family apartment communities with 4,051 homes located in California. The communities included in the joint venture were valued at $2.4 billion, or approximately $592,000 per apartment home. The joint venture has existing property debt of $1.22 billion and an implied equity value of $1.18 billion. In exchange for a 39% equity interest, we received $461 million. We retain ownership of 61% of the joint venture and will control and operate the communities in exchange for property and asset management fees. We evaluated the joint venture and concluded that we will continue to consolidate these communities. The difference between the consideration received and the carrying value of the interest sold was recognized in additional paid-in capital. Apartment Community Acquisition On August 25, 2020, we acquired Hamilton on the Bay for $89.6 million. The assets and liabilities of Hamilton on the Bay were retained by Aimco concurrent with the Separation and are not included on our consolidated balance sheets as of December 31, 2020. Apartment Community Dispositions Sold apartment communities during the years ended December 31, 2020, 2019, and 2018, are summarized below (dollars in thousands): 2020 2019 2018 Number of apartment communities sold 2 12 4 Number of apartment homes sold 485 3,596 1,334 Gain on dispositions of real estate (1) $ 119,215 $ 503,168 $ 175,213 (1) During the year ended December 31, 2019, gain on dispositions of real estate includes the gain recognized upon the expiration of indemnification liabilities related to the sale of our Asset Management business. The apartment communities sold were predominantly located outside of our primary markets or in lower-rated locations within primary markets and had average revenues per apartment home significantly below those of our retained portfolio. During the year ended December 31, 2018, we also sold for $590.0 million our Asset Management business and our four affordable apartment communities located in the Hunters Point area of San Francisco. The sale resulted in a gain of $500.3 million and net cash proceeds of $512.2 million, after payment of transaction costs and repayment of property-level debt. Additionally, we sold our interest in the entities owning the La Jolla Cove property. We provided seller financing with a stated value of $48.6 million and received net cash proceeds of approximately $5.0 million during the year ended December 31, 2020. The net amount of seller financing associated with this transaction was retained by Aimco in the Separation. In addition to the apartment communities we sold during the current period, from time to time we may be marketing for sale certain communities that are inconsistent with our long-term investment strategy. At the end of each reporting period we evaluate whether such communities meet the criteria to be classified as held for sale. As of December 31, 2020, no communities were classified as held for sale.

Discontinued Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2020
Discontinued Operations And Disposal Groups [Abstract]
Discontinued Operations	Note 4 — Discontinued Operations The financial results attributable to apartment communities retained by the Spinnee for all periods presented have been classified as discontinued operations within the consolidated financial statements. Major assets and liabilities related to discontinued operations at December 31, 2019 are shown below (in thousands): 2019 ASSETS: Net real estate $ 936,168 Cash and cash equivalents 6,443 Restricted cash 4,717 Investment in unconsolidated real estate partnerships 12,741 Other assets 62,627 Total assets of discontinued operations $ 1,022,696 LIABILITIES: Non-recourse property debt, net $ 492,785 Deferred tax liability 144,033 Accrued liabilities and other 26,571 Total liabilities of discontinued operations $ 663,389 Summarized results of discontinued operations for the years ended December 31, 2020, 2019, and 2018 are shown below (in thousands): 2020 2019 2018 REVENUES: Rental and other property revenues $ 144,757 $ 143,692 $ 132,163 OPERATING EXPENSES: Property operating expenses 51,710 49,502 45,372 Depreciation and amortization 72,729 62,887 48,392 Other expenses (income), net 1,897 257 (1,208 ) Total operating expenses 126,336 112,646 92,556 Interest income 2,076 2,125 1,592 Interest expense (17,972 ) (17,918 ) (20,829 ) Income from unconsolidated real estate partnerships 764 802 940 Income before income tax benefit (expense) 3,289 16,055 21,310 Income tax benefit (expense) 7,939 3,440 (319 ) Income from discontinued operations, net of tax 11,228 19,495 20,991 Net loss (income) attributable to noncontrolling interests in consolidated real estate partnerships 404 189 (5 ) Net income from discontinued operations attributable to AIR $ 11,632 $ 19,684 $ 20,986 Through December 15, 2020, we incurred transaction costs of $57.0 million related to the Separation, all of which are reflected in other expenses, net on our consolidated statement of operations for the year ended December 31, 2020. Transaction costs primarily consist of third-party advisory, consulting, legal and professional services, as well as other items that are incremental in nature and that were specifically related to the Separation. After the Separation, we and the Spinnee are operating as two, focused and independent companies. We entered into various separation and transition services agreements with the Spinnee that provide for a framework of our relationship with the Spinnee after the Separation, including: (i) a separation agreement setting forth the mechanics of the Separation, the key provisions relating to the separation of our assets and liabilities from those of the Spinnee, and certain organizational matters and conditions; (ii) an employee matters agreement to allocate liabilities and responsibilities relating to employment matters, teammate compensation, and benefits plans and programs, and other related matters; (iii) Property Management Agreements pursuant to which we will provide property management and related services at a majority of the properties owned or leased by the Spinnee in exchange for a fee based on an agreed percentage of revenue collected; (iv) Master Services Agreement pursuant to which we will provide the Spinnee with customary administrative and support services on an ongoing basis in exchange for payment for the fully-burdened costs (including internal allocated costs); and (v) a Master Leasing Agreement pursuant to which the Spinnee may enter into leases with us pursuant to which the Spinnee, at its option, may redevelop, develop, or lease-up apartment communities. The Property Management Agreement, the Master Service Agreement, and the Master Lease Agreement may be terminated in accordance with the respective agreements. The Master Leasing Agreement governs any future leasing arrangements between us and the Spinnee. The initial term of the Master Leasing Agreement is 18 months, with automatic annual extensions (subject to each party’s right to terminate upon notice prior to the end of any such extension term). The initial annual rent for any leased property is based a calculation derived from the then-current fair market value of the subject property and market NOI cap rates, subject to certain adjustments, and is further subject to periodic escalation as set forth in the applicable lease, and the other terms thereof, including the initial term and extensions on an arm’s-length basis, as defined in the Master Lease Agreement . The Spinnee has the right to terminate any such lease prior to the end of its term once the leased property is stabilized. In connection with an early termination, we have an option to pay the Spinnee an amount equal to the difference between the then-current fair market value of such property and the initial fair market value of such property at the time of the lease inception, at a small discount. If we do not exercise an option, the Spinnee will have the right to sell the property to a third party with us guaranteed to receive an amount equal to the fair market value of the property at the time of the lease inception, or the Spinnee may elect to purchase the property at a purchase price equal to the fair market value thereof at the time of lease inception (and may subsequently sell the property to a third party, subject to our right of first refusal during the first year following the Spinnee ’s acquisition). On January 1, 2021 , the Master Lease Agreement commenced and we had four redevelopment properties leased to the Spinnee .

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	Note 5 — Leases Lessor Arrangements The majority of lease payments we receive from our residents and tenants are fixed. We receive variable payments from our residents and commercial tenants primarily for utility reimbursements. Our total lease income, included in continuing operations, was comprised of the following amounts for all operating leases for the year ended December 31, 2020 (in thousands): 2020 2019 Fixed lease income $ 677,060 $ 722,146 Variable lease income 43,588 46,494 Straight-line rent write-off (1) (2,850 ) — Total lease income $ 717,798 $ 768,640 (1) We monitor the collectability of all unpaid rent amounts. The onset of COVID-19 and the anticipated economic slowdown resulted in a $2.9 million write-off of accrued straight-line rent during the year ended December 31, 2020 In response to the economic effects of the COVID-19 pandemic and governmental lockdowns, many jurisdictions where our communities are located have enacted protections for residents and commercial tenants, including government-mandated rent deferrals, rent freezes, repayment extensions, fee abatement measures or concessions, and prohibitions on lease terminations or evictions for tenants. Some states and municipalities are also implementing rental assistance programs and encouraging landlord-tenant negotiations. On April 10, 2020, the FASB issued a Staff Q&A to respond to some frequently asked questions about accounting for lease concessions, including deferrals or reductions of future lease payments. Consequently, in accordance with the Staff Q&A issued by the FASB, we may elect to record rent relief when granted rather than over the remaining term of the lease. In general, our commercial leases have options to extend for a certain period of time at the tenant’s option. Future minimum annual rental payments we are contractually obligated to receive under commercial leases, excluding such extension options, are as follows as of December 31, 2020 (in thousands): 2021 $ 13,184 2022 13,488 2023 12,584 2024 11,170 2025 9,513 Thereafter 47,476 Total $ 107,415 Generally, our residential leases do not provide extension options and, as of December 31, 2020, have an average remaining term of 8.5 months. Commencing on January 1, 2021, we had leased four redevelopment properties to Aimco, resulting in $25.3 million of expected 2021 lease payments. The lease payments related to the four redevelopment properties have not been included in the table above. Lessee Arrangements Beginning in 2019, we recognize right of use assets and related lease liabilities, which are included in other assets and accrued liabilities and other, respectively, in our consolidated balance sheets. We estimated the value of the lease liabilities using a discount rate equivalent to the rate we would pay on a secured borrowing with similar terms to the lease. On October 1, 2019, we revised our estimate of the incremental borrowing rate, which resulted in a reduction of our right of use assets and related lease liabilities for ground leases. The adjustment recorded to our right of use assets and lease liabilities did not impact our consolidated statements of operations. Substantially all of the payments under our ground and office leases are fixed. We exclude o ptions to extend the lease in our minimum lease terms unless the option is reasonably to be exercised. Our total lease cost for ground and office leases f As of December 31, 2020, the ground and office leases have weighted-average remaining terms of 73.3 years and 7.6 years, respectively, and weighted-average discount rates of 6.6% and 3.6%, respectively. Minimum annual rental payments under these operating leases, reconciled to the lease liability included in accrued liabilities and other in our consolidated balance sheets, are as follows (in thousands): Operating Lease Future Minimum Rent 2021 $ 4,548 2022 4,280 2023 3,727 2024 3,749 2025 3,770 Thereafter 421,228 Total $ 441,302 Less: Discount (385,933 ) Total lease liability $ 55,369

Non-Recourse Property Debt and

Non-Recourse Property Debt and Credit Agreement	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Non-Recourse Property Debt and Credit Agreement	Note 6 — Non-Recourse Property Debt and Credit Agreement Non-Recourse Property Debt We finance apartment communities in our portfolio primarily using property-level, non-recourse, long-dated, fixed-rate, amortizing debt. The following table summarizes non-recourse property debt as of December 31, 2020 and 2019 (dollars in thousands): Outstanding Balance as of December 31, Latest Maturity Date Interest Rate Range Weighted-Average Interest Rate 2020 2019 Fixed-rate property debt January 1, 2055 2.42% to 6.01% 3.55% $ 3,631,588 $ 3,740,648 Variable-rate property debt July 13, 2033 1.09% to 1.15% 1.12% 14,505 14,505 Total non-recourse property debt 3,646,093 3,755,153 Debt issuance costs, net of accumulated amortization (17,857 ) (17,348 ) Non-recourse property debt, net $ 3,628,236 $ 3,737,805 Principal and interest on fixed-rate debt are generally payable monthly or in monthly interest-only payments with balloon payments due at maturity. As of December 31, 2020, our fixed-rate property debt was secured by 57 apartment communities that had an aggregate net book value of $3.7 billion. Principal and interest on variable-rate debt are generally payable in semi-annual installments with balloon payments due at maturity. As of December 31, 2020, our variable-rate property debt was secured by three apartment communities that had an aggregate net book value of $14.5 million. These non-recourse property debt instruments contain covenants common to the type of borrowing, and as of December 31, 2020, we were in compliance with all such covenants. As of December 31, 2020, the scheduled principal amortization and maturity payments for the non-recourse property debt were as follows (in thousands): Amortization Maturities Total 2021 $ 67,922 $ 35,848 $ 103,770 2022 68,836 201,264 270,100 2023 63,939 160,670 224,609 2024 63,112 154,685 217,797 2025 57,883 355,013 412,896 Thereafter 322,412 2,094,509 2,416,921 Total $ 644,104 $ 3,001,989 $ 3,646,093 Credit Agreement On December 15, 2020, in connection with the Separation, we decreased the maximum borrowing capacity of our revolving credit facility from $800.0 million to $600.0 million, reflecting reduced borrowing needs with the elimination of redevelopment and development projects. In addition to the revolving credit facility, our credit agreement also includes a $350.0 million term loan, which was secured on April 20, 2020. The loan matures on April 20, 2021, includes a one-year extension option, and currently bears interest at a 30-day LIBOR plus 1.60%, with a 50 basis point LIBOR floor. Proceeds from the loan were used primarily to repay borrowings on our revolving credit facility. Borrowings against our revolving credit facility bear interest at a rate set forth on a pricing grid, which rate varies based on our credit rating as assigned by specified rating agencies (LIBOR plus 1.00%, or, at our option, a base rate plus 0.0% as of December 31, 2020). Swing line loans will bear interest at the base rate plus the applicable margin. The revolving credit agreement matures on January 22, 2022. As of December 31, 2020 and 2019, we had $265.6 million and $275.0 million, respectively, of outstanding borrowings under our revolving credit facility. The interest rate on our outstanding borrowings was 1.46% and 3.00% as of December 31, 2020 and 2019, respectively. As of December 31, 2020, after outstanding borrowings and $23.7 million of undrawn letters of credit backed by the revolving credit facility, our available borrowing capacity was $310.7 million. We have agreed to maintain a fixed charge coverage ratio of 1.40x, as well as other covenants customary for similar revolving credit arrangements . We expect to remain in compliance with these covenants

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 7 — Commitments and Contingencies Commitments We have entered into various construction-related contracts. As of December 31, 2020, our commitments under these contracts totaled approximately $18.0 million. The duration of these commitments is expected to be less than 24 months. We enter into certain commitments for future purchases of goods and services in connection with the operations of our apartment communities. Those commitments generally have terms of one year or less and reflect expenditure levels comparable to our historical expenditures. Legal Matters In addition to the matters described below, we are a party to various legal actions and administrative proceedings arising in the ordinary course of business, some of which are covered by our general liability insurance program, and none of which we expect to have a material adverse effect on our consolidated financial condition, results of operations or cash flows. Environmental Various federal, state and local laws subject apartment community owners or operators to liability for management, and the costs of removal or remediation, of certain potentially hazardous materials that may be present in the land or buildings of an apartment community. Such laws often impose liability without regard to fault or whether the owner or operator knew of, or was responsible for, the presence of such materials. The presence of, or the failure to manage or remediate properly, these materials may adversely affect occupancy at such apartment communities as well as the ability to sell or finance such apartment communities. In addition, governmental agencies may bring claims for costs associated with investigation and remediation actions. Moreover, private plaintiffs may potentially make claims for investigation and remediation costs they incur or for personal injury, disease, disability or other infirmities related to the alleged presence of hazardous materials. In addition to potential environmental liabilities or costs associated with our current apartment communities, we may also be responsible for such liabilities or costs associated with communities we acquire or manage in the future, or apartment communities we no longer own or operate. We are engaged in discussions with the Environmental Protection Agency (“EPA”), regarding contaminated groundwater near an Indiana apartment community that has not been owned by us since 2008, for which we have recognized a contingent liability. The contamination allegedly derives from a dry cleaner that operated on our former property, prior to our ownership. We undertook a voluntary remediation of the dry cleaner contamination under state oversight. In 2016, EPA listed our former community and a number of residential communities in the vicinity on the National Priorities List (“NPL”) (i.e., as a Superfund site). In May 2018, we prevailed on our federal judicial appeal vacating the Superfund listing. We continue to work with EPA to formulate an agreed order to reimburse EPA costs and finish clean up of the site outside the Superfund program. Although the outcome of this process is uncertain, we do not expect the resolution to have a material adverse effect on our consolidated financial condition, results of operations, or cash flows. We have a contingent liability related to a property in Lake Tahoe, California. An entity owned by us was the former general partner of a now-dissolved partnership that previously owned a site where a laundromat, with a self-service dry-cleaning machine, operated. That entity and the current property owner have been remediating the site since 2009, under the oversight of the Lahontan Regional Water Quality Control Board (“Lahontan”). In May 2017, Lahontan issued a final cleanup and abatement order that names four potentially-responsible parties, acknowledges that there may be additional responsible parties, and requires the named parties to perform additional groundwater investigation and corrective actions with respect to onsite and offsite contamination. We appealed the final order, and on June 1, 2020, the court vacated the Order against us. However, there are still civil suits pending related to this contingent liability. Although the outcome of this process is uncertain, we do not expect the resolution to have a material adverse effect on our consolidated financial condition, results of operations, or cash flows. For legal liabilities that relate to occurrences prior to the Separation, including environmental liabilities related to properties that were no longer owned by AIR’s Predecessor or AIR at the time of the Separation, pursuant to the terms of the Separation Agreement, the operating partnership of the Spinnee will be responsible for the first $17.5 million of such liabilities, in the aggregate, and AIR Operating Partnership will be responsible for any such liabilities in excess of $17.5 million. We have determined that our legal obligations to remove or remediate certain potentially hazardous materials may be conditional asset retirement obligations, as defined by GAAP. Except in limited circumstances where the asset retirement activities are expected to be performed in connection with a planned construction project or apartment community casualty, we believe that the fair value of our asset retirement obligations cannot be reasonably estimated due to significant uncertainties in the timing and manner of settlement of those obligations. Asset retirement obligations that are reasonably estimable as of December 31, 2020, are immaterial to our consolidated financial statements.

AIR Equity

AIR Equity	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
AIR Equity	Note 8 — AIR Equity On December 14, 2020, our Board of Directors amended and restated our charter. Immediately following the Separation, our Board of Directors is authorized to issue up to 1,021,175,000 shares of common stock and 1,000,000 shares of preferred stock. We completed the Separation, which was effected by way of a pro rata distribution, in which stockholders received one share of AIR common stock for every one share of Aimco common stock held as of the close of business on the record date. Common Stock During the years ended December 31, 2020, 2019, and 2018, we declared regular quarterly cash dividends per common share of $0.41, $0.39, and $0.38, respectively, excluding dividends declared as part of the special dividend. On January 28, 2021, our Board of Directors declared quarterly cash dividends of $0.43 per share of AIR Common Stock. This amount is payable on February 26, 2021, to stockholders of record on February 12, 2021. 2020 Special Stock Dividend and Reverse Stock Split 2020 property sales, including the California joint venture, generated taxable gains in excess of our regular quarterly dividend. On October 21, 2020, the Board of Directors of AIR’s Predecessor declared a special dividend and reverse stock split on its Common Stock in which every 1.23821 common share was combined into one common share, effective on the close of business on November 30, 2020. The special dividend consisted of $121.8 million in cash and 35.4 million shares of AIR’s Predecessor Common Stock. The special dividend was paid on November 30, 2020 to stockholders of record as of November 4, 2020. The special dividend amount of $0.82 per share included the regular quarterly cash dividend for the fourth quarter of 2020 and accelerated into 2020 what would have been AIR’s Predecessor’s first regular quarterly cash dividend for 2021. 2019 Special Stock Dividend and Reverse Stock Split On February 3, 2019, our Board of Directors authorized a reverse stock split, in which every 1.03119 then AIR’s Predecessor common share was combined into one common share, effective at the close of business on February 20, 2019. On the same date, our Board of Directors also declared a special dividend on the Common Stock that consisted of $67.1 million in cash, 4.5 million shares of Common Stock, and $0.4 million of cash paid in lieu of issuing fractional units. We paid the special dividend on March 22, 2019, to stockholders of record as of February 22, 2019. The special dividend amount included the regular quarterly cash dividend of $0.39 per share. As a result of the 2020 and 2019 reverse stock splits, the total number of shares outstanding after the stock dividend and reverse split was unchanged from the number of shares outstanding immediately prior to the two actions. Preferred Stock As of December 31, 2020, we had a single class of perpetual preferred stock outstanding, our Class A Preferred Stock, with twenty shares issued and outstanding and a balance of $2.0 million. The Preferred Stock was issued in connection with the Separation. Our Class A Preferred Stock has a $0.01 per share par value, is senior to our Common Stock, has a liquidation preference per share of $100.0 thousand and is redeemable at our option on or after December 15, 2025. The holders of Preferred Stock are generally not entitled to vote on matters submitted to stockholders. Dividends in an amount per share equal to 8.5% per annum are subject to declaration by our Board of Directors.

Partners' Capital

Partners' Capital	12 Months Ended
	Dec. 31, 2020
Partners Capital [Abstract]
Partners' Capital	Note 9 —Partners’ Capital Separation from Aimco On December 15, 2020, AIR Operating Partnership completed the Separation, which was effected through a pro rata distribution of all of the outstanding common limited partnership units of Aimco Operating Partnership to holders of AIR Operating Partnership common limited partnership units and AIR Operating Partnership Class I High Performance partnership units as of the close of business on December 5, 2020. Stockholders of AIR’s Predecessor received one share of Class A common stock of AIR for every one share of Class A common stock of AIR’s Predecessor held as of the close of business on the record date, and received cash in lieu of fractional shares of Class A common stock of AIR. Partnership Preferred Units Owned by AIR At December 31, 2020, AIR Operating Partnership had Class A outstanding preferred units similar to AIR’s Preferred Stock discussed in Note 8. All Class A Partnership Preferred Units are senior to the AIR Operating Partnership common partnership units. Distributions on all Partnership Preferred Units are subject to being declared by the General Partner. The Partnership Preferred Units are redeemable by the AIR Operating Partnership only in connection with a concurrent redemption by AIR of the corresponding AIR Preferred Stock held by unrelated parties. Redeemable Preferred OP Units The AIR Operating Partnership has outstanding various classes of redeemable preferred OP Units. As of December 31, 2020 and 2019, the AIR Operating Partnership had the following classes of preferred OP Units (stated at their redemption values, in thousands, except unit and per unit data): Distributions per Annum Units Issued and Outstanding Redemption Values Class of Preferred Units Percent Per Unit 2020 2019 2020 2019 Class One 8.75 % $ 8.00 90,000 90,000 $ 8,229 $ 8,229 Class Two 1.92 % $ 0.48 11,122 11,122 278 278 Class Three 7.88 % $ 1.97 1,313,927 1,338,524 32,848 33,463 Class Four 8.00 % $ 2.00 644,954 644,954 16,124 16,124 Class Six 8.50 % $ 2.13 773,693 773,693 19,342 19,342 Class Seven 7.87 % $ 1.97 26,150 26,150 654 654 Class Nine 6.00 % $ 1.50 78,956 78,956 1,974 1,974 Class Ten 6.00 % $ 1.50 — 680,000 — 17,000 Total 2,938,802 3,643,399 $ 79,449 $ 97,064 Each class of preferred OP Units is currently redeemable at the holders’ option. The AIR Operating Partnership, at its sole discretion, may settle such redemption requests in cash or cause AIR to issue shares of its Common Stock with a value equal to the redemption price. In the event the AIR Operating Partnership requires AIR to issue shares of Common Stock to settle a redemption request, the AIR Operating Partnership would issue to AIR a corresponding number of common OP Units. The AIR Operating Partnership has a redemption policy that requires cash settlement of redemption requests for the preferred OP Units, subject to limited exceptions. Subject to certain conditions, the Class Four and Class Six preferred OP Units may be converted into common OP Units. These redeemable units are classified within temporary equity in AIR’s consolidated balance sheets and within temporary capital in the AIR Operating Partnership’s consolidated balance sheets. During the years ended December 31, 2020, 2019, and 2018, approximately 705,000, 169,000 and 10,000 preferred OP Units, respectively, were redeemed in exchange for cash, and no preferred OP Units were redeemed in exchange for shares of AIR Common Stock or common OP Units. The following table presents a reconciliation of the AIR Operating Partnership’s preferred OP Units during the year ended December 31, 2020 (in thousands): 2020 Balance at January 1 $ 97,064 Preferred distributions (7,019 ) Redemption of preferred units and other (17,615 ) Net income 7,019 Balance at December 31 $ 79,449 AIR Operating Partnership Partners’ Capital Common Partnership Units In the AIR Operating Partnership’s consolidated balance sheets, the common partnership units held by AIR are classified within Partners’ Capital as General Partner and Special Limited Partner capital and the common OP Units are classified within Limited Partners’ capital. In AIR’s consolidated balance sheets, the common OP Units are classified within permanent equity as common noncontrolling interests in the AIR Operating Partnership. Common partnership units held by AIR are not redeemable whereas common OP Units are redeemable at the holders’ option, subject to certain restrictions, on the basis of one common OP Unit for either one share of Common Stock or cash equal to the fair value of a share of Common Stock at the time of redemption. AIR has the option to deliver shares of Common Stock in exchange for all or any portion of the common OP Units tendered for redemption. When a limited partner redeems a common OP Unit for Common Stock, Limited Partners’ capital is reduced and the General Partner and Special Limited Partners’ capital is increased. During the years ended December 31, 2020, 2019, and 2018, approximately 64,000, 129,000 and 224,000 common OP Units, respectively, were redeemed in exchange for cash. During the years ended December 31, 2020 and 2019, 159,000 and 127,000 common OP Units were redeemed in exchange for shares of Common Stock. No common OP Units were redeemed in exchange for AIR Common Stock during the year ended December 31, 2018. The holders of the common OP Units receive distributions, prorated from the date of issuance, in an amount equivalent to the dividends paid to holders of Common Stock. During the years ended December 31, 2020, 2019, and 2018, the Aimco Operating Partnership declared regular quarterly distributions per common unit of $0.41, $0.39 and $0.38, respectively, excluding distributions declared as part of the special distribution. On October 21, 2020, the Board of Directors authorized a reverse unit split and special distribution in the same form and with the same timing as the reverse stock split and special dividend discussed in Note 8 above. The special distribution to the holders of Aimco Operating Partnership common partnership units consisted of $128.7 million in cash and 35.4 million common partnership units. Total common partnership units outstanding prior to and following both transactions was unchanged. On February 3, 2019, the Board of Directors authorized a reverse unit split and special distribution on the same form and with the same timing as the reverse stock split and special dividend discussed in Note 8 above. The special distribution to the holders of Aimco Operating Partnership common partnership units consisted of $72.7 million in cash, 4.8 million common partnership units and $0.4 million of cash paid in lieu of issuing fractional units. Total common partnership units outstanding prior to and following both transactions was unchanged.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation	Note 10 — Share-Based Compensation We have a stock award and incentive program to attract and retain officers and independent directors. On December 15, 2020, we adopted our 2020 Stock Award and Incentive Plan (the “Plan”). As of December 31, 2020, approximately three million shares were available for issuance under the Plan. The total number of shares available for issuance under this plan may increase due to any forfeiture, cancellation, exchange, surrender, termination or expiration of an award outstanding under the Plan. Awards under the Plan may be in the form of incentive stock options, non-qualified stock options, or other types of awards as authorized under the Plan. We grant stock options and restricted stock awards that are subject to time-based vesting and require continuous employment, typically over a period of four years from the grant date, and we refer to these awards as Time-Based Stock Options and Time-Based Restricted Stock, respectively. We also grant stock options, restricted stock awards, and two forms of long-term incentive partnership units (“LTIP units”), that vest conditioned on AIR’s total shareholder return (“TSR”), relative to the NAREIT Equity Apartment Index ( 60 % weighting) and the MSCI US REIT Index ( 40 % weighting) over a forward-looking performance period of three years . We refer to these awards as TSR Stock Options, TSR Restricted Stock, TSR LTIP I units, and TSR LTIP II units. Vested LTIP II units may be converted at the holders’ option to LTIP Units for a strike price over a term of 10 years . Earned TSR-based awards, if any, will vest 50 % on each of the third anniversary and fourth anniversary of the grant date, based on continued employment. Our Time-Based Stock Options and TSR Stock Options expire generally 10 years from the date of grant . We recognize compensation cost associated with Time-Based awards ratably over the requisite service periods, which are typically four years. We recognize compensation cost related to the TSR-based awards, which have graded vesting periods, over the requisite service period for each separate vesting tranche of the award, commencing on the grant date. The value of the TSR-based awards takes into consideration the probability that the market condition will be achieved; therefore previously recorded compensation cost is not adjusted in the event that the market condition is not achieved and awards do not vest. We had Time-Based Stock Options, Time-Based Restricted Stock, TSR Stock Options, TSR Restricted Stock, TSR LTIP I units, Time-Based LTIP I units, and TSR LTIP II units outstanding as of December 31, 2020. The annual activity related to our stock and unit awards are immaterial. In connection with the Separation, we entered into an Employee Matters Agreement to modify all outstanding stock and unit awards granted to the teammates of AIR’s Predecessor. Under the agreement, holders of AIR’s Predecessor stock and unit awards received AIR stock and unit awards. Generally, AIR awards retain the same terms and vesting conditions as the original AIR’s Predecessor awards. Holders of AIR’s Predecessor TSR stock options and TSR LTIP II awards, will have modified exercise price adjusted by a ratio specified in the Employee Matters Agreement. Following the Separation, compensation expense related to replacement awards for the teammates retained by Aimco is recognized by Aimco. The compensation expense related to replacement awards for teammates of AIR is recognized by AIR. Our plans are administered by the Compensation and Human Resources Committee of the Board of Directors. In the case of stock options, the exercise price of the options granted may not be less than the fair market value of a share of Common Stock at the date of grant. Total compensation cost recognized for share-based awards was as follows for the years ended December 31, 2020, 2019, and 2018 (in thousands): 2020 2019 2018 Share-based compensation expense (1) $ 8,295 $ 8,146 $ 8,550 Capitalized share-based compensation (2) 946 962 1,215 Total share-based compensation (3) $ 9,241 $ 9,108 $ 9,765 (1) Amounts are recorded in general and administrative expenses on the consolidated statements of operations. (2) Amounts are recorded in building and improvements on the consolidated balance sheets. (3) Amounts are recorded in additional paid-in capital and common noncontrolling interests in the AIR Operating Partnership on the AIR consolidated balance sheets, and in general partner and special limited partner and limited partners on the AIR Operating Partnership consolidated balance sheets. As of December 31, 2020, total unvested compensation cost not yet recognized was $9.9 million. We expect to recognize this compensation over a weighted-average period of approximately 1.6 years. TSR and Time-Based Stock Options As of December 31, 2020, we had stock options outstanding of 827,853, which had an aggregate intrinsic value of $3.1 million and a weighted-average remaining contractual term of 4.8 years. We had 733,942 of stock options exercisable as of December 31, 2020, which had an aggregate intrinsic value of $2.9 million and a weighted-average remaining contractual term of 4.9 years. The intrinsic value of a stock option represents the amount by which the current price of the underlying stock exceeds the exercise price of the option. These options will be settled in Aimco and AIR common stock in accordance with the Employee Matters Agreement. During 2020, we granted TSR Stock Options with a weighted-average grant date fair value of $8.15. Time-Based Restricted Stock Awards As of December 31, 2020, we had 94,663 shares unvested at a weighted-average grant date fair value of $45.51. TSR Restricted Stock Awards As of December 31, 2020, we had 222,848 of shares unvested based on the target performance payout, at a weighted-average grant date fair value of $49.43. These shares will be settled in Aimco and AIR common stock in accordance with the Employee Matters Agreement. TSR LTIP II Units As of December 31, 2020, we had 1,112,342 of TSR LTIP II units outstanding, at a weighted-average grant date fair value of $9.58. These units will be settled in Aimco and AIR units in accordance with the Employee Matters Agreement. Determination of Grant-Date Fair Value of Awards Options are granted with an exercise price at the fair market value of our common stock on the date of grant and, subject to employment, which is generally 10 years from the date of grant. Factors considered are the simulated stock price as well as total shareholder return relative to both the NAREIT Equity Apartment Index and the MSCI US REIT Index. We estimated the fair value of TSR-based awards granted in 2020, 2019, and 2018 using a Monte Carlo model with the assumptions set forth in the table below. The risk-free interest rate reflects the annualized yield of a zero coupon United States Treasury security with a term equal to the expected term of the awards. The expected dividend yield reflects expectations regarding cash dividend amounts per share paid on our Common Stock during the expected term of the awards. Expected volatility reflects an average of the historical volatility of our Common Stock during the historical period commensurate with the expected term of the award that ended on the date of grant, and the implied volatility is calculated from observed call option contracts closest to the expected term. The derived vesting period of TSR Restricted Stock and TSR LTIP I units was determined based on the graded vesting terms. The expected term of the TSR-options and TSR LTIP II units was based on historical exercises and post-vesting terminations. The valuation assumptions for the 2020, 2019, and 2018 grants were as follows: 2020 2019 2018 Grant date market value of a common share $ 53.26 $ 49.24 $ 40.95 Risk-free interest rate 1.48% - 1.58% 2.59% - 2.66% 2.32% - 2.68% Dividend yield 2.93 % 3.09 % 3.52 % Expected volatility 15.82% - 16.84% 19.08% - 19.24% 17.64% - 18.02% Derived vesting period of TSR Restricted Stock and TSR LTIP I units 3.5 years 3.4 years 3.4 years Weighted average expected term of TSR Stock Options and LTIP II units 5.9 years 5.8 years 5.6 years The grant date fair value for the Time-Based awards reflects the closing price of a share of our Common Stock on the grant date.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Note 11 — Income Taxes During the year ended December 31, 2020, and consistent with AIR’s simplified business structure and strategy, we have elected to treat one of our taxable subsidiaries as a REIT under the Code, commencing with its initial taxable year ended December 31, 2021. As a result, AIR will incur less income taxes on a consolidated basis, providing more cash for distributions and other corporate uses. As a REIT, this subsidiary will generally be allowed a deduction for dividends that it pays, and therefore, will not be subject to United States federal corporate income tax on the taxable income that is currently distributed to stockholders, however, may be subject to certain state gross income and franchise taxes, as well as taxes on any undistributed income and federal and state corporate taxes on any income earned. The income tax effects of a REIT conversion for financial reporting purposes are reflected in the period in which all significant actions necessary to qualify as a REIT are completed and the entity has committed to becoming a REIT, including (i) obtaining approval from the appropriate parties; (ii) purging through a distribution to stockholders any accumulated earnings and profits from its operations as a C corporation; and (iii) having any remaining actions for the entity to achieve REIT status be perfunctory legal and administrative matters. The only remaining action for this subsidiary to achieve REIT status is to file its federal income tax return for tax year ended December 31, 2021 as a REIT on its required filing date. All significant actions necessary to qualify as a REIT were met as of December 31, 2020, and as such its deferred tax assets and liabilities as of that date were adjusted to reflect a tax rate of zero percent, resulting in the elimination of its deferred tax assets and liabilities as of December 31, 2020. Significant components of our deferred tax liabilities and assets are as follows (in thousands): December 31, 2020 2019 Deferred tax liabilities: Real estate and real estate partnership basis differences $ (13 ) $ — Deferred tax assets: Real estate and real estate partnership basis differences — 17,316 Tax credit carryforwards — 53,776 Net operating, capital, and other loss carryforwards — 6,147 Accruals and expenses — 6,138 Management contracts and other — 1,905 Total deferred tax assets — 85,282 Valuation allowance — (4,766 ) Net deferred tax (liabilities) assets $ (13 ) $ 80,516 As of December 31, 2020, net deferred tax liabilities were presented in accrued liabilities and other in our consolidated balance sheets. As of December 31, 2019, net deferred tax assets were presented in other assets in our consolidated balance sheets. A reconciliation of the beginning and ending balance of our unrecognized tax benefits is presented below (in thousands): 2020 2019 2018 Balance at January 1 $ 5,080 $ 2,618 $ 2,476 Additions based on tax position taken in current year (1) (4,625 ) 2,758 — Additions based on tax positions related to prior years (218 ) 226 142 Reductions as a result of a lapse of the applicable statutes 4,203 (522 ) — Balance at December 31 $ 4,440 $ 5,080 $ 2,618 (1) Reduction in unrecognized tax benefit for the year ended December 31, 2020, is related to tax positions taken as a result of the Separation. Because the statute of limitations has not yet elapsed, our United States federal income tax returns for the year ended December 31, 2017, and subsequent years and certain of our state income tax returns for the year ended December 31, 2017, and subsequent years are currently subject to examination by the IRS or other taxing authorities. If recognized, the unrecognized benefit would affect the effective rate. Our policy is to include any interest and penalties related to income taxes within the income tax line item in our consolidated statements of operations. Significant components of the income tax benefit or expense are as follows and are classified within income tax benefit in our consolidated statements of operations for the years ended December 31, 2020, 2019, and 2018 (in thousands): 2020 2019 2018 Current: Federal $ 6,271 $ 5,204 $ 11,269 State 8,637 8,558 10,218 Total current 14,908 13,762 21,487 Deferred: Federal (7,691 ) (8,575 ) (29,243 ) State (2,694 ) (4,882 ) (5,590 ) Revaluation of deferred taxes due to change in tax rate 90,914 — — Total deferred 80,529 (13,457 ) (34,833 ) Total expense (benefit) $ 95,437 $ 305 $ (13,346 ) Consolidated income from continuing operations or loss from continuing operations subject to tax consists of pretax income or loss from the continuing operations of our TRS entities and income and gains retained by the continuing operations of the REIT. For the years ended December 31, 2020, 2019, and 2018, we had consolidated net loss from continuing operations subject to tax of $16.7 million, net loss from continuing operations subject to tax of $13.5 million, and net income from continuing operations subject to tax of $133.3 million, respectively. The reconciliation of income tax attributable to continuing operations computed at the United States statutory rate to income tax benefit is shown below (dollars in thousands): 2020 2019 2018 Amount Percent Amount Percent Amount Percent Tax (benefit) provision at United States statutory rates on consolidated income or loss from continuing operations subject to tax $ (3,516 ) 21.0 % $ (2,836 ) 21.0 % $ 33,296 21.0 % State income tax expense, net of federal tax (benefit) expense (1,964 ) 11.7 % 3,935 (29.1 %) 11,933 7.7 % Effect of permanent differences 434 (2.6 %) (139 ) 1.0 % 302 0.2 % Tax effect of intercompany transactions (1) — — % — — % (33,250 ) (21.0 %) Tax credits (296 ) 1.8 % (667 ) 4.9 % (6,897 ) (4.4 %) Tax reform revaluation — — % — — % 288 0.2 % Decrease in valuation allowance — — % (164 ) 1.2 % (20,434 ) (12.9 %) Separation 7,596 (45.4 %) — — % — — % TRS REIT election (2) 90,914 (543.1 %) — — % — — % Other 2,269 (13.6 %) 176 (1.3 %) 1,416 0.9 % Total income tax expense (benefit) $ 95,437 (570.2 %) $ 305 (2.3 %) $ (13,346 ) (8.3 %) (1) Effective January 1, 2017, we adopted a new accounting standard applicable to intercompany asset transfers. 2018 includes the tax benefit to establish the initial deferred tax asset from the intercompany transfer of a portion of the Asset Management business between the AIR Operating Partnership and TRS entities. (2) Consistent with our simplified business structure and strategy, we have elected to treat one of our taxable subsidiaries as a REIT, resulting in the non-cash removal of deferred tax asset balances for the year ended December 31, 2020. For income tax purposes, dividends paid to holders of Common Stock primarily consist of ordinary income, capital gains, qualified dividends, unrecaptured Section 1250 gains, and return of capital, or a combination thereof. For the years ended December 31, 2020, 2019, and 2018, dividends per share held for the entire year were estimated to have the following tax attributes: 2020 2019 2018 (unaudited) Amount Percentage Amount Percentage Amount Percentage Ordinary income $ 2.41 6.0 % $ 0.66 20.7 % $ 0.51 33.4 % Capital gains 15.00 37.4 % 1.29 40.4 % 0.93 61.2 % Qualified dividends 0.48 1.2 % 0.66 20.7 % — — % Unrecaptured Section 1250 gain 6.74 16.8 % 0.58 18.2 % 0.08 5.4 % Return of capital 15.49 38.6 % — — % — — % Total $ 40.12 100.0 % $ 3.19 100.0 % $ 1.52 100.0 %

Earnings per Share and per Unit

Earnings per Share and per Unit	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings per Share and per Unit	Note 12 — Earnings per Share and per Unit AIR and the AIR Operating Partnership calculate basic earnings per common share and basic earnings per common unit based on the weighted-average number of shares of Common Stock and common partnership units outstanding. We calculate diluted earnings per share and diluted earnings per unit taking into consideration dilutive common stock and common partnership unit equivalents and dilutive convertible securities outstanding during the period. Our common stock and common partnership unit equivalents include options to purchase shares of Common Stock, which, if exercised, would result in AIR’s issuance of additional shares and the AIR Operating Partnership’s issuance to AIR of additional common partnership units equal to the number of shares purchased under the options. These equivalents also include unvested TSR Restricted Stock awards that do not meet the definition of participating securities, which would result in an increase in the number of shares of Common Stock and common partnership units outstanding equal to the number of the shares that vest. Common partnership unit equivalents also include unvested long-term incentive partnership units. We include in the denominator securities with dilutive effect in calculating diluted earnings per share and per unit during these periods. Our Time-Based Restricted Stock awards receive non-forfeitable dividends similar to shares of Common Stock and common partnership units prior to vesting, and our TSR LTIP I units and TSR LTIP II units receive non-forfeitable distributions based on specified percentages of the distributions paid to common partnership units prior to vesting and conversion. The unvested restricted shares and units related to these awards are participating securities. We include the effect of participating securities in basic and diluted earnings per share and unit computations using the two-class method of allocating distributed and undistributed earnings when the two-class method is more dilutive than the treasury stock method. In our consolidated statement of operations, noncontrolling interest in consolidated real estate partnerships is related to both continuing and discontinuing operations. For purposes of our earnings per share calculation, we have appropriately allocated the noncontrolling interest in consolidated real estate partnerships for all periods presented. Please refer to Note 4 for detail of noncontrolling interest in consolidated real estate partnerships associated with discontinued operations. Reconciliations of the numerator and denominator in the calculations of basic and diluted earnings per share and per unit for the years ended December 31, 2020, 2019, and 2018 are as follows (in thousands, except per share and per unit data): Year Ended December 31, 2020 Income (Numerator) Shares (Denominator) Per Share Amount Basic and Diluted Earnings per Share: Loss from continuing operations attributable to AIR $ (115,961 ) 122,446 $ (0.94 ) Income from discontinued operations attributable to AIR 11,632 122,446 0.09 Net loss attributable to AIR common stockholders $ (104,329 ) 122,446 $ (0.85 ) Diluted Earnings per Share: Effect of dilutive securities — — — Net loss attributable to AIR common stockholders $ (104,329 ) 122,446 $ (0.85 ) Year Ended December 31, 2019 Income (Numerator) Shares (Denominator) Per Share Amount Basic Earnings per Share: Income from continuing operations attributable to AIR $ 446,460 119,307 $ 3.75 Income from discontinued operations attributable to AIR 19,684 119,307 0.16 Net income attributable to AIR common stockholders $ 466,144 119,307 $ 3.91 Diluted Earnings per Share: Effect of dilutive securities — 226 (0.01 ) Net income attributable to AIR common stockholders $ 466,144 119,533 $ 3.90 Year Ended December 31, 2018 Income (Numerator) Shares (Denominator) Per Share Amount Basic Earnings per Share: Income from continuing operations attributable to AIR $ 635,611 122,097 $ 5.21 Income from discontinued operations attributable to AIR 20,986 122,097 0.17 Net income attributable to AIR common stockholders $ 656,597 122,097 $ 5.38 Diluted Earnings per Share: Effect of dilutive securities — 146 (0.01 ) Net income attributable to AIR common stockholders $ 656,597 122,243 $ 5.37 Year Ended December 31, 2020 Income (Numerator) Shares (Denominator) Per Unit Amount Basic and Diluted Earnings per unit: Loss from continuing operations attributable to the AIR Operating Partnership $ (121,399 ) 128,775 $ (0.94 ) Income from discontinued operations attributable to the AIR Operating Partnership 11,632 128,775 0.09 Net loss attributable to the AIR Operating Partnership's common unitholders $ (109,767 ) 128,775 $ (0.85 ) Diluted Earnings per unit: Effect of dilutive securities — — — Net loss attributable to the AIR Operating Partnership's common unitholders $ (109,767 ) 128,775 $ (0.85 ) Year Ended December 31, 2019 Income (Numerator) Shares (Denominator) Per Unit Amount Basic Earnings per unit: Income from continuing operations attributable to the AIR Operating Partnership $ 472,493 125,893 $ 3.75 Income from discontinued operations attributable to the AIR Operating Partnership 19,684 125,893 0.16 Net income attributable to the AIR Operating Partnership's common unitholders $ 492,177 125,893 $ 3.91 Diluted Earnings per unit: Effect of dilutive securities — 271 (0.01 ) Net income attributable to the AIR Operating Partnership's common unitholders $ 492,177 126,164 $ 3.90 Year Ended December 31, 2018 Income (Numerator) Shares (Denominator) Per Unit Amount Basic Earnings per unit: Income from continuing operations attributable to the AIR Operating Partnership $ 669,888 128,323 $ 5.22 Income from discontinued operations attributable to the AIR Operating Partnership 20,986 128,323 0.16 Net income attributable to the AIR Operating Partnership's common unitholders $ 690,874 128,323 $ 5.38 Diluted Earnings per unit: Effect of dilutive securities — 146 — Net income attributable to the AIR Operating Partnership's common unitholders $ 690,874 128,469 $ 5.38 As discussed in Note 9, the AIR Operating Partnership has various classes of preferred OP Units, which may be redeemed at the holders’ option. The AIR Operating Partnership may redeem these units for cash, or at its option, shares of Common Stock. As of December 31, 2020, these preferred OP Units were potentially redeemable for approximately 2.1 million shares of Common Stock (based on the period end market price), or cash. The AIR Operating Partnership has a redemption policy that requires cash settlement of redemption requests for the preferred OP Units, subject to limited exceptions. Accordingly, we have excluded these securities from earnings per share and unit computations for the periods presented above.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 13 — Fair Value Measurements Recurring Fair Value Measurements We measure at fair value on a recurring basis our investment in the securitization trust that holds certain of our property debt, which These investments are presented within other assets in the consolidated balance sheets. Our investments in AFS debt securities are classified within Level 2 of the GAAP fair value hierarchy. We estimate the fair value of these investments using an income and market approach with primarily observable inputs, including yields and other information regarding similar types of investments, and adjusted for certain unobservable inputs specific to these investments. The fair value of the positions that pay interest currently typically moves in an inverse relationship with movements in interest rates. The fair value of the first loss position is primarily correlated to collateral quality and demand for similar subordinate commercial mortgage-backed securities. During the year ended December 31, 2020, we paid an upfront premium of $12.1 million for the option to enter into an interest rate swap at a future date. This interest rate option, or swaption, provides partial protection against our refinancing interest rate risk and is intended to mitigate interest rate increases between now and 2024. We receive a cash settlement in the future if the prevailing interest rate is higher than the 1.68% strike price. The amount of future cash settlement is limited if the prevailing interest rate exceeds 2.78%. Alternatively, if interest rates were to decrease below the specified strike price, we would not receive a cash settlement. We measure at fair value on a recurring basis our interest rate option, which is presented in other assets in our consolidated balance sheets. Our interest rate option is classified within Level 2 of the GAAP fair value hierarchy, and we estimate its fair value using pricing models that rely on observable market information, including contractual terms, market prices, and interest rate yield curves. The fair value adjustment is included in earnings in other expense, net, in our consolidated statements of operations. Changes in fair value are reflected as a non-cash transaction in adjustments to arrive at cash flows from operations, and the upfront premium is reflected in other financing in our consolidated statements of cash flows. The following table summarizes fair value for our AFS debt securities and interest rate option as of December 31, 2020 and 2019 (in thousands): As of December 31, 2020 2019 Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 AFS debt securities $ 100,151 $ — $ 100,151 $ — $ 94,251 $ — $ 94,251 $ — Interest rate option $ 13,177 $ — $ 13,177 $ — $ — $ — $ — $ — Nonrecurring Fair Value Measurements As of December 31, 2020, assets measured at fair value on a nonrecurring basis in our consolidated balance sheets consist of a real estate asset that was written down to its estimated fair value for impairment purposes. Our estimate of fair value was determined using valuations performed by third-party specialists, unobservable inputs are classified as Level 3 within the GAAP fair value hierarchy. As of December 31, 2020, the fair value of the real estate asset measured on a nonrecurring basis was $34.4 million. There were no assets measured at fair value on a nonrecurring basis as of December 31, 2019. Refer to Note 2 for further detail on the non-cash impairment. Financial Assets and Liabilities Not Measured at Fair Value We believe that the carrying value of the consolidated amounts of cash and cash equivalents, restricted cash, accounts receivable and accounts payable approximated their fair value as of December 31, 2020 and 2019, due to their relatively short-term nature and high probability of realization. The carrying amounts of the notes receivable from Aimco, the term loan, and the revolving credit facility also approximated their estimated fair value as of December 31, 2020, and 2019. We estimate the fair value of our non-recourse property debt using an income and market approach, including comparison of the contractual terms to observable and unobservable inputs such as market interest rate risk spreads, contractual interest rates, remaining periods to maturity, collateral quality, and loan to value ratios on similarly encumbered apartment communities within our portfolio. We classify the fair value of our non-recourse property debt within Level 2 of the GAAP valuation hierarchy based on the significance of certain of the observable inputs used to estimate its fair value. The following table summarizes carrying value and fair value of our non-recourse property debt as of December 31, 2020 and 2019 (in thousands): As of December 31, 2020 2019 Carrying Value Fair Value Carrying Value Fair Value Non-recourse property debt $ 3,646,093 $ 3,730,621 $ 3,755,153 $ 3,798,789

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Variable Interest Entities	Note 14 — Variable Interest Entities Consolidated Entities AIR consolidates the AIR Operating Partnership, a VIE of which AIR is the primary beneficiary. AIR, through the AIR Operating Partnership, consolidates all VIEs for which it is the primary beneficiary. All of the VIEs the AIR Operating Partnership consolidates own interests in one or more apartment communities and are typically structured to generate a return for their partners through the operation and ultimate sale of the communities. The AIR Operating Partnership is the primary beneficiary in the limited partnerships in which it is the sole decision maker and has a substantial economic interest. The table below summarizes apartment community information regarding VIEs consolidated by the AIR Operating Partnership. As of December 31, 2020 2019 VIEs with interests in apartment communities 5 5 Apartment communities owned by VIEs 16 5 Apartment homes in communities owned by VIEs 5,369 2,016 Assets of the AIR Operating Partnership’s consolidated VIEs must first be used to settle the liabilities of such consolidated VIEs. These consolidated VIEs’ creditors do not have recourse to the general credit of the AIR Operating Partnership. Assets and liabilities of VIEs, excluding those of the AIR Operating Partnership and those properties that remain with the Spinnee, are summarized in the table below (in thousands): As of December 31, 2020 2019 Assets Net real estate $ 1,125,315 $ 201,425 Cash and cash equivalents $ 10,548 $ 4,153 Restricted cash $ 8,818 $ 2,047 Other assets $ 23,870 $ 18,731 Liabilities Non-recourse property debt secured by AIR communities, net $ 1,278,318 $ 175,550 Accrued liabilities and other $ 34,038 $ 23,780 Unconsolidated Entities We have an interest in a partnership that owns Parkmerced Apartments, which meets the definition of a VIE. However, we are not the primary beneficiary and do not consolidate this partnership. In connection with the Separation, Aimco was allocated economic ownership of the $275.0 million mezzanine investment and the option to acquire a 30% equity interest in the partnership. The investment accrues interest at 10% per annum with a five-year five-year

Business Segments

Business Segments	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Business Segments	Note 15 — Business Segments During the year ended December 31, 2020, we revised our operating segments in accordance with how our chief operating decision maker (“CODM”) evaluates our business. We now have two segments: Same Store and Other Real Estate. Our Same Store segment includes communities that: (i) are owned and managed by AIR; (ii) had reached a stabilized level of operations as of January 1, 2019, and maintained it throughout the current and the comparable prior periods; and (iii) are not expected to be sold within 12 months. Our Other Real Estate segment includes communities that do not meet the criteria to be classified as Same Store. Communities included in discontinued operations are excluded from our evaluation of segment performance, as they are no longer included in information used by our CODM. Our CODM uses proportionate property net operating income to assess the operating performance of our communities. Proportionate property net operating income reflects our share of rental and other property revenues, excluding utility reimbursements, less direct property operating expenses, net of utility reimbursements, for consolidated communities. In our consolidated statements of operations, utility reimbursements are included in rental and other property revenues, in accordance with GAAP . As of December 31, 2020, our Same Store segment included 91 apartment communities with 25,201 apartment homes and our Other Real Estate segment included eight apartment communities with 1,391 apartment homes. The following tables present the rental and other property revenues, property operating expenses, proportionate property net operating income, and income (loss) from continuing operations before income tax benefit (expense) of our segments on a proportionate basis, excluding amounts related to communities sold or communities included in discontinued operations for the years ended December 31, 2020, 2019, and 2018 (in thousands): Same Store Other Real Estate Proportionate and Other Adjustments (1) Corporate and Amounts Not Allocated to Segments (2) Consolidated Year ended December 31, 2020: Rental and other property revenues $ 655,853 $ 13,194 $ 44,370 $ 6,139 $ 719,556 Property operating expenses 182,967 9,319 31,555 25,195 249,036 Other operating expenses not allocated to segments (3) — — — 488,461 488,461 Total operating expenses 182,967 9,319 31,555 513,656 737,497 Proportionate property net operating income (loss) 472,886 3,875 12,815 (507,517 ) (17,941 ) Other items included in income (loss) before income tax expense (4) — — — (1,194 ) (1,194 ) Income (loss) from continuing operations before income tax expense $ 472,886 $ 3,875 $ 12,815 $ (508,711 ) $ (19,135 ) Same Store Other Real Estate Proportionate and Other Adjustments (1) Corporate and Amounts Not Allocated to Segments (2) Consolidated Year ended December 31, 2019: Rental and other property revenues $ 689,255 $ 13,731 $ 27,235 $ 40,381 $ 770,602 Property operating expenses 184,150 8,614 25,190 43,287 261,241 Other operating expenses not allocated to segments (3) — — — 383,635 383,635 Total operating expenses 184,150 8,614 25,190 426,922 644,876 Proportionate property net operating income (loss) 505,105 5,117 2,045 (386,541 ) 125,726 Other items included in income (loss) before income tax expense (4) — — — 363,111 363,111 Income (loss) from continuing operations before income tax expense $ 505,105 $ 5,117 $ 2,045 $ (23,430 ) $ 488,837 Same Store Other Real Estate Proportionate and Other Adjustments (1) Corporate and Amounts Not Allocated to Segments (2) Consolidated Year ended December 31, 2018: Rental and other property revenues $ 645,917 $ 22,368 $ 25,936 $ 146,026 $ 840,247 Property operating expenses 174,708 9,863 23,842 56,311 264,724 Other operating expenses not allocated to segments (3) — — — 399,377 399,377 Total operating expenses 174,708 9,863 23,842 455,688 664,101 Proportionate property net operating income (loss) 471,209 12,505 2,094 (309,662 ) 176,146 Other items included in income before income tax benefit (4) — — — 506,120 506,120 Income from continuing operations before income tax benefit $ 471,209 $ 12,505 $ 2,094 $ 196,458 $ 682,266 (1) Represents adjustments for the noncontrolling interests in consolidated real estate partnerships’ share of the results of consolidated communities in our segments, which are included in the related consolidated amounts, but excluded from proportionate property net operating income for our segment evaluation. Also includes the reclassification of utility reimbursements from revenues to property operating expenses for the purpose of evaluating segment results. Utility reimbursements are included in rental and other property revenues in our consolidated statements of operations prepared in accordance with GAAP. (2) Includes the operating results of apartment communities sold during the periods shown or held for sale at the end of the period, if any, and the operating results of communities owned by consolidated partnerships served by our Asset Management business prior to its sale in July 2018. Also includes property management expenses and casualty gains and losses, which are included in consolidated property operating expenses and are not part of our segment performance measure. The write-off of straight-line rent receivables, recognized due to the impact of COVID-19 and the resulting economic impact on our commercial tenants, are included in consolidated rental and property revenues and are not included in our measurement of segment performance for the year ended December 31, 2020 . (3) Includes property operating expenses of partnerships served by our Asset Management business prior to its sale in July 2018, depreciation and amortization, general and administrative expenses, and other operating expenses, which may include provision for real estate impairment loss and write-offs of deferred leasing commissions, which are not included in our measure of segment performance. (4) Includes separation costs, gain on dispositions of real estate and the Asset Management business, interest income, and interest expense. The assets of our segments and the consolidated assets not allocated to our segments were as follows (in thousands): December 31, 2020 December 31, 2019 Same Store $ 4,545,476 $ 4,692,491 Other Real Estate 636,296 478,839 Corporate and other assets (1) 1,047,506 715,230 Assets of discontinued operations — 1,022,696 Total consolidated assets $ 6,229,278 $ 6,909,256 (1) Includes the assets not allocated to our segments, primarily corporate assets, assets of apartment communities which were sold or classified as held for sale as of December 31, 2020, and our notes receivable from Aimco. For the years ended December 31, 2020, 2019, and 2018, capital additions related to our segments were as follows (in thousands): 2020 2019 2018 Same Store $ 109,461 $ 200,979 $ 218,986 Other Real Estate 219,280 162,024 71,079 Total capital additions (1) $ 328,741 $ 363,003 $ 290,065 (1) Includes amounts related to commercial properties.

Unaudited Summarized Consolidat

Unaudited Summarized Consolidated Quarterly Information	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Unaudited Summarized Consolidated Quarterly Information	Note 16 — Unaudited Summarized Consolidated Quarterly Information AIR AIR’s summarized unaudited consolidated quarterly information for the years ended December 31, 2020 and 2019, is provided below (in thousands, except per share amounts): Quarter 2020 First Second Third Fourth Total revenues $ 186,043 $ 181,643 $ 178,124 $ 173,746 Net income (loss) from continuing operations $ 4,911 $ 40,079 $ (27,393 ) $ (132,169 ) Net income from discontinued operations $ 4,066 $ 3,125 $ 2,578 $ 1,459 Net income (loss) attributable to AIR common stockholders $ 6,679 $ 39,212 $ (25,046 ) $ (125,174 ) Net income (loss) attributable to AIR per common share – basic $ 0.06 $ 0.33 $ (0.21 ) $ (0.96 ) Net income (loss) attributable to AIR per common share – diluted $ 0.06 $ 0.33 $ (0.21 ) $ (0.96 ) Quarter 2019 First Second Third Fourth Total revenues $ 196,447 $ 190,311 $ 192,013 $ 191,831 Net income from continuing operations $ 285,951 $ 63,818 $ 85 $ 138,678 Net income from discontinued operations $ 5,344 $ 6,178 $ 3,885 $ 4,088 Net income attributable to AIR common stockholders $ 271,568 $ 59,234 $ 2,003 $ 133,339 Net income attributable to AIR per common share – basic $ 2.33 $ 0.49 $ 0.02 $ 1.11 Net income attributable to AIR per common share – diluted $ 2.33 $ 0.49 $ 0.02 $ 1.11 The AIR Operating Partnership The AIR Operating Partnership’s summarized unaudited consolidated quarterly information for the years ended December 31, 2020 and 2019, is provided below (in thousands, except per unit amounts): Quarter 2020 First Second Third Fourth Total revenues $ 186,043 $ 181,643 $ 178,124 $ 173,746 Net income (loss) from continuing operations $ 4,911 $ 40,079 $ (27,393 ) $ (132,169 ) Net income from discontinued operations $ 4,066 $ 3,125 $ 2,578 $ 1,459 Net income (loss) attributable to the Partnership's common unitholders $ 7,047 $ 41,319 (26,387 ) $ (131,746 ) Net income (loss) attributable to the Partnership's common unitholders per common unit – basic $ 0.06 $ 0.33 $ (0.21 ) $ (0.96 ) Net income (loss) attributable to the Partnership's common unitholders per common unit – diluted $ 0.06 $ 0.33 $ (0.21 ) $ (0.96 ) Quarter 2019 First Second Third Fourth Total revenues $ 196,447 $ 190,311 $ 192,013 $ 191,831 Net income from continuing operations $ 285,951 $ 63,818 $ 85 $ 138,678 Net income from discontinued operations $ 5,344 $ 6,178 $ 3,885 $ 4,088 Net income attributable to the Partnership's common unitholders $ 286,639 $ 62,817 $ 2,138 $ 140,583 Net income attributable to the Partnership's common unitholders per common unit – basic $ 2.33 $ 0.50 $ 0.02 $ 0.90 Net income attributable to the Partnership's common unitholders per common unit – diluted $ 2.33 $ 0.50 $ 0.02 $ 0.90

Schedule III_ Real Estate and

Schedule III: Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2020
Real Estate And Accumulated Depreciation Disclosure [Abstract]
Schedule III: Real Estate and Accumulated Depreciation	APARTMENT INCOME REIT CORP. AIMCO PROPERTIES, L.P. SCHEDULE III: REAL ESTATE AND ACCUMULATED DEPRECIATION December 31, 2020 (In Thousands Except Apartment Home Data) (2) As of December 31, 2020 (1) Initial Cost Cost Capitalized (4) Apartment Date Year Apartment Buildings and Subsequent to Buildings and (3) Accumulated Total Cost (5) Apartment Community Name Type Consolidated Location Built Homes Land Improvements Consolidation Land Improvements Total Depreciation (AD) Net of AD Encumbrances Same Store Sales: 100 Forest Place High Rise Dec 1997 Oak Park, IL 1987 234 $ 2,664 $ 18,815 $ 10,235 $ 2,664 $ 29,050 $ 31,714 $ (16,704 ) $ 15,010 $ 33,832 182-188 Columbus Avenue Mid Rise Feb 2007 New York, NY 1910 32 19,123 3,300 5,629 19,123 8,929 28,052 (4,993 ) 23,059 13,336 1582 First Avenue High Rise Mar 2005 New York, NY 1900 17 4,281 752 548 4,281 1,300 5,581 (719 ) 4,862 2,177 21 Fitzsimons Mid Rise Aug 2014 Aurora, CO 2008 600 12,864 104,720 31,377 12,864 136,097 148,961 (33,121 ) 115,840 87,612 234 East 88th Street Mid Rise Jan 2014 New York, NY 1900 20 2,448 4,449 841 2,448 5,290 7,738 (1,661 ) 6,077 — 306 East 89th Street High Rise Jul 2004 New York, NY 1930 20 2,680 1,006 1,105 2,680 2,111 4,791 (1,153 ) 3,638 1,776 311 & 313 East 73rd Street Mid Rise Mar 2003 New York, NY 1904 34 5,678 1,609 604 5,678 2,213 7,891 (1,721 ) 6,170 — 322-324 East 61st Street High Rise Mar 2005 New York, NY 1900 40 6,372 2,224 1,477 6,372 3,701 10,073 (2,054 ) 8,019 3,266 3400 Avenue of the Arts Mid Rise Mar 2002 Costa Mesa, CA 1987 770 57,241 65,506 90,493 57,241 155,999 213,240 (96,067 ) 117,173 139,094 452 East 78th Street High Rise Jan 2004 New York, NY 1900 12 1,982 608 538 1,982 1,146 3,128 (534 ) 2,594 — 464-466 Amsterdam & 200-210 W. 83rd Street Mid Rise Feb 2007 New York, NY 1910 71 25,553 7,101 11,476 25,553 18,577 44,130 (6,681 ) 37,449 19,653 510 East 88th Street High Rise Jan 2004 New York, NY 1900 20 3,163 1,002 642 3,163 1,644 4,807 (788 ) 4,019 — 514-516 East 88th Street High Rise Mar 2005 New York, NY 1900 36 6,282 2,168 1,565 6,282 3,733 10,015 (2,033 ) 7,982 3,540 518 East 88th Street Mid Rise Jan 2014 New York, NY 1900 20 2,233 4,315 630 2,233 4,945 7,178 (1,592 ) 5,586 — 777 South Broad Street Mid Rise May 2018 Philadelphia, PA 2010 146 6,986 67,512 3,317 6,986 70,829 77,815 (6,896 ) 70,919 55,496 Avery Row Mid Rise Dec 2018 Arlington, VA 2013 67 8,165 21,348 2,097 8,165 23,445 31,610 (1,980 ) 29,630 — Axiom Mid Rise Apr 2015 Cambridge, MA 2015 115 — 63,612 2,883 — 66,495 66,495 (14,037 ) 52,458 31,501 Bay Parc Plaza High Rise Sep 2004 Miami, FL 2000 474 22,680 41,847 41,403 22,680 83,250 105,930 (29,744 ) 76,186 75,046 Bay Ridge at Nashua Garden Jan 2003 Nashua, NH 1984 412 3,262 40,713 16,929 3,262 57,642 60,904 (29,360 ) 31,544 49,717 Bayberry Hill Estates Garden Aug 2002 Framingham, MA 1971 424 19,944 35,945 25,376 19,944 61,321 81,265 (33,451 ) 47,814 43,393 Bent Tree Apartments Garden Feb 2018 Centreville, VA 1986 748 46,975 113,695 30,349 46,975 144,044 191,019 (16,284 ) 174,735 59,777 Boston Lofts High Rise Apr 2001 Denver, CO 1890 158 3,446 20,589 6,501 3,446 27,090 30,536 (15,054 ) 15,482 — Boulder Creek Garden Jul 1994 Boulder, CO 1973 221 754 7,730 19,320 754 27,050 27,804 (20,010 ) 7,794 37,194 Broadcast Center Garden Mar 2002 Los Angeles, CA 1990 279 29,407 41,244 32,598 29,407 73,842 103,249 (34,493 ) 68,756 94,978 Broadway Lofts High Rise Sep 2012 San Diego, CA 1909 84 5,367 14,442 8,187 5,367 22,629 27,996 (7,543 ) 20,453 11,056 Burke Shire Commons Garden Mar 2001 Burke, VA 1986 360 4,867 23,617 18,810 4,867 42,427 47,294 (28,554 ) 18,740 55,809 Calhoun Beach Club High Rise Dec 1998 Minneapolis, MN 1928 332 11,708 73,334 63,689 11,708 137,023 148,731 (87,464 ) 61,267 — Canyon Terrace Garden Mar 2002 Saugus, CA 1984 130 7,508 6,601 6,592 7,508 13,193 20,701 (7,961 ) 12,740 — Charlesbank Apartment Homes Mid Rise Sep 2013 Watertown, MA 2012 44 3,399 11,726 1,115 3,399 12,841 16,240 (3,463 ) 12,777 — Chestnut Hall High Rise Oct 2006 Philadelphia, PA 1923 315 12,338 14,299 14,513 12,338 28,812 41,150 (13,748 ) 27,402 34,985 Columbus Avenue Mid Rise Sep 2003 New York, NY 1880 59 35,527 9,450 9,155 35,527 18,605 54,132 (13,318 ) 40,814 23,986 Creekside Garden Jan 2000 Denver, CO 1974 328 3,189 12,698 7,328 3,189 20,026 23,215 (14,096 ) 9,119 10,792 Crescent at West Hollywood, The Mid Rise Mar 2002 West Hollywood, CA 1985 130 15,765 10,215 8,683 15,765 18,898 34,663 (13,024 ) 21,639 38,643 Flamingo Point, Center Tower High Rise Sep 1997 Miami Beach, FL 2003 513 15,179 29,358 203,209 15,179 232,567 247,746 (107,729 ) 140,017 — Flamingo Point, South Tower High Rise Sep 1997 Miami Beach, FL 1960 222 — — 74,578 — 74,578 74,578 (12,504 ) 62,074 — Four Quarters Habitat Garden Jan 2006 Miami, FL 1976 336 2,379 17,199 34,208 2,379 51,407 53,786 (34,722 ) 19,064 49,792 Foxchase Garden Dec 1997 Alexandria, VA 1940 2,113 15,496 96,062 63,632 15,496 159,694 175,190 (94,709 ) 80,481 — Georgetown Garden Aug 2002 Framingham, MA 1964 207 12,351 13,168 5,068 12,351 18,236 30,587 (9,270 ) 21,317 — Georgetown II Mid Rise Aug 2002 Framingham, MA 1958 72 4,577 4,057 2,145 4,577 6,202 10,779 (4,032 ) 6,747 — Heritage Park Escondido Garden Oct 2000 Escondido, CA 1986 196 1,055 7,565 3,988 1,055 11,553 12,608 (7,576 ) 5,032 5,590 Heritage Park Livermore Garden Oct 2000 Livermore, CA 1988 167 — 10,209 2,157 — 12,366 12,366 (8,893 ) 3,473 5,810 Heritage Village Anaheim Garden Oct 2000 Anaheim, CA 1986 196 1,832 8,541 3,393 1,832 11,934 13,766 (7,768 ) 5,998 6,788 Hidden Cove Garden Jul 1998 Escondido, CA 1983 334 3,043 17,616 10,456 3,043 28,072 31,115 (17,083 ) 14,032 64,757 Hidden Cove II Garden Jul 2007 Escondido, CA 1986 118 12,849 6,530 5,071 12,849 11,601 24,450 (6,061 ) 18,389 25,183 Hillcreste Garden Mar 2002 Century City, CA 1989 315 35,862 47,216 15,897 35,862 63,113 98,975 (31,011 ) 67,964 60,310 Horizons West Apartments Mid Rise Dec 2006 Pacifica, CA 1970 78 8,887 6,377 3,562 8,887 9,939 18,826 (4,666 ) 14,160 — Hunt Club Garden Sep 2000 Gaithersburg, MD 1986 336 17,859 13,149 12,592 17,859 25,741 43,600 (16,198 ) 27,402 — Indian Oaks Garden Mar 2002 Simi Valley, CA 1986 254 24,523 15,801 11,439 24,523 27,240 51,763 (15,790 ) 35,973 58,955 Indigo High Rise Aug 2016 Redwood City, CA 2016 463 26,932 296,116 5,569 26,932 301,685 328,617 (46,343 ) 282,274 182,161 Island Club Garden Oct 2000 Oceanside, CA 1986 592 18,027 28,654 20,499 18,027 49,153 67,180 (32,779 ) 34,401 91,631 Latrobe High Rise Jan 2003 Washington, D.C. 1980 175 3,459 9,103 13,196 3,459 22,299 25,758 (14,426 ) 11,332 25,462 Laurel Crossing Garden Jan 2006 San Mateo, CA 1971 418 49,474 17,756 15,114 49,474 32,870 82,344 (17,785 ) 64,559 102,565 Lincoln Place (6) Garden Oct 2004 Venice, CA 1951 795 128,332 10,439 341,037 44,197 351,476 395,673 (156,957 ) 238,716 180,859 Locust on the Park High Rise May 2018 Philadelphia, PA 1911 152 5,292 53,823 5,801 5,292 59,624 64,916 (5,982 ) 58,934 35,000 Malibu Canyon Garden Mar 2002 Calabasas, CA 1986 698 69,834 53,438 39,822 69,834 93,260 163,094 (54,343 ) 108,751 158,950 (2) As of December 31, 2020 (1) Initial Cost Cost Capitalized (4) Apartment Date Year Apartment Buildings and Subsequent to Buildings and (3) Accumulated Total Cost (5) Apartment Community Name Type Consolidated Location Built Homes Land Improvements Consolidation Land Improvements Total Depreciation (AD) Net of AD Encumbrances Mariners Cove Garden Mar 2002 San Diego, CA 1984 500 $ — $ 66,861 $ 16,354 $ — $ 83,215 $ 83,215 $ (44,288 ) $ 38,927 $ — Meadow Creek Garden Jul 1994 Boulder, CO 1968 332 1,435 24,533 9,575 1,435 34,108 35,543 (22,157 ) 13,386 — Merrill House High Rise Jan 2000 Falls Church, VA 1964 159 1,836 10,831 8,319 1,836 19,150 20,986 (11,359 ) 9,627 — Mezzo High Rise Mar 2015 Atlanta, GA 2008 94 4,292 34,178 2,171 4,292 36,349 40,641 (8,419 ) 32,222 — Monterey Grove Garden Jun 2008 San Jose, CA 1999 224 34,325 21,939 16,440 34,325 38,379 72,704 (14,771 ) 57,933 48,698 Ocean House on Prospect Mid Rise Apr 2013 La Jolla, CA 1970 53 12,528 18,805 16,070 12,528 34,875 47,403 (10,586 ) 36,817 — One Ardmore Mid Rise Apr 2019 Ardmore, PA 2019 110 4,929 61,631 1,865 4,929 63,496 68,425 (3,911 ) 64,514 30,448 One Canal High Rise Sep 2013 Boston, MA 2016 310 — 15,873 182,092 — 197,965 197,965 (37,688 ) 160,277 106,576 Pacific Bay Vistas (6) Garden Mar 2001 San Bruno, CA 1987 308 28,694 62,460 40,897 23,354 103,357 126,711 (42,650 ) 84,061 102,554 Pacifica Park Garden Jul 2006 Pacifica, CA 1977 104 12,970 6,579 8,688 12,970 15,267 28,237 (8,272 ) 19,965 37,264 Palazzo at Park La Brea, The Mid Rise Feb 2004 Los Angeles, CA 2002 521 48,362 125,464 51,848 48,362 177,312 225,674 (95,304 ) 130,370 216,916 Palazzo East at Park La Brea, The Mid Rise Mar 2005 Los Angeles, CA 2005 611 72,578 136,503 31,959 72,578 168,462 241,040 (87,863 ) 153,177 187,917 Park Towne Place High Rise Apr 2000 Philadelphia, PA 1959 940 10,472 47,301 354,675 10,472 401,976 412,448 (185,618 ) 226,830 193,163 Peachtree Park Garden Jan 1996 Atlanta, GA 1969 303 4,684 11,713 14,067 4,684 25,780 30,464 (17,572 ) 12,892 26,813 Preserve at Marin Mid Rise Aug 2011 Corte Madera, CA 1964 126 13,516 30,132 83,001 13,516 113,133 126,649 (37,040 ) 89,609 34,603 Riverloft High Rise Oct 1999 Philadelphia, PA 1910 184 2,120 11,286 38,205 2,120 49,491 51,611 (28,035 ) 23,576 — Rosewood Garden Mar 2002 Camarillo, CA 1976 152 12,430 8,060 6,265 12,430 14,325 26,755 (8,102 ) 18,653 30,452 Royal Crest Estates Garden Aug 2002 North Andover, MA 1970 588 51,292 36,808 27,537 51,292 64,345 115,637 (38,311 ) 77,326 79,730 Saybrook Pointe Garden Dec 2014 San Jose, CA 1995 324 32,842 84,457 26,088 32,842 110,545 143,387 (23,844 ) 119,543 107,347 Shenandoah Crossing Garden Sep 2000 Fairfax, VA 1984 640 18,200 57,198 23,189 18,200 80,387 98,587 (63,435 ) 35,152 — SouthStar Lofts High Rise May 2018 Philadelphia, PA 2014 85 1,780 37,428 901 1,780 38,329 40,109 (3,706 ) 36,403 29,028 Springwoods at Lake Ridge Garden Jul 2002 Woodbridge, VA 1984 180 5,587 7,284 2,782 5,587 10,066 15,653 (4,462 ) 11,191 — Sterling Apartment Homes, The Garden Oct 1999 Philadelphia, PA 1961 534 8,871 55,365 117,915 8,871 173,280 182,151 (100,897 ) 81,254 138,021 Stonecreek Club Garden Sep 2000 Germantown, MD 1984 240 13,593 9,347 6,520 13,593 15,867 29,460 (11,595 ) 17,865 — The Left Bank Mid Rise May 2018 Philadelphia, PA 1929 282 — 130,893 19,781 — 150,674 150,674 (14,018 ) 136,656 78,925 Township At Highlands Town Home Nov 1996 Centennial, CO 1985 161 1,536 9,773 13,101 1,536 22,874 24,410 (13,967 ) 10,443 — Tremont Mid Rise Dec 2014 Atlanta, GA 2009 78 5,274 18,011 3,270 5,274 21,281 26,555 (4,974 ) 21,581 — Vantage Pointe Mid Rise Aug 2002 Swampscott, MA 1987 96 4,748 10,089 2,559 4,748 12,648 17,396 (6,020 ) 11,376 — Villa Del Sol Garden Mar 2002 Norwalk, CA 1972 120 7,476 4,861 5,423 7,476 10,284 17,760 (6,332 ) 11,428 — Villas at Park La Brea, The Garden Mar 2002 Los Angeles, CA 2002 250 8,630 48,871 20,720 8,630 69,591 78,221 (37,027 ) 41,194 48,156 Villas of Pasadena Mid Rise Jan 2006 Pasadena, CA 1973 92 9,693 6,818 4,975 9,693 11,793 21,486 (5,990 ) 15,496 20,500 Vivo High Rise Jun 2016 Cambridge, MA 2015 91 6,450 35,974 6,054 6,450 42,028 48,478 (14,322 ) 34,156 19,297 Waterways Village Garden Jun 1997 Aventura, FL 1994 180 4,504 11,064 16,798 4,504 27,862 32,366 (15,034 ) 17,332 — Waverly Apartments Garden Aug 2008 Brighton, MA 1970 103 7,920 11,347 6,860 7,920 18,207 26,127 (8,447 ) 17,680 — Windrift Garden Mar 2001 Oceanside, CA 1987 404 24,960 17,590 21,022 24,960 38,612 63,572 (27,153 ) 36,419 71,199 Windsor Park Garden Mar 2001 Woodbridge, VA 1987 220 4,279 15,970 5,437 4,279 21,407 25,686 (14,071 ) 11,615 — Total Same Store Sales 25,201 $ 1,333,899 $ 2,913,666 $ 2,581,861 $ 1,244,424 $ 5,495,527 $ 6,739,951 $ (2,344,168 ) $ 4,395,783 $ 3,588,079 Other Real Estate: 236-238 East 88th Street High Rise Jan 2004 New York, NY 1900 42 $ 8,820 $ 2,914 $ 12,311 $ 8,820 $ 15,225 $ 24,045 $ (2,195 ) $ 21,850 $ — 240 West 73rd Street (6) High Rise Sep 2004 New York, NY 1900 200 68,109 12,140 17,138 20,828 29,278 50,106 (10,568 ) 39,538 — 707 Leahy Garden Apr 2007 Redwood City, CA 1973 110 15,444 7,909 35,135 15,444 43,044 58,488 (7,630 ) 50,858 — Eldridge Townhomes Town Home Sep 2017 Elmhurst, IL 2018 58 3,105 — 30,998 3,105 30,998 34,103 (614 ) 33,489 — Flamingo Point, North Tower High Rise Sep 1997 Miami Beach, FL 1960 366 17,248 19,450 217,222 17,248 236,672 253,920 (82,561 ) 171,359 — Fremont Mid Rise Sep 2018 Denver, CO 2020 253 1,830 — 89,196 1,830 89,196 91,026 (1,215 ) 89,811 — Parc Mosaic Garden Dec 2014 Boulder, CO 1970 226 15,300 — 109,626 15,300 109,626 124,926 (6,554 ) 118,372 58,014 Other (7) 136 14,616 — 77,683 14,616 77,683 92,299 — 92,299 — Total Other Real Estate 1,391 $ 144,472 $ 42,413 $ 589,309 $ 97,191 $ 631,722 $ 728,913 $ (111,337 ) $ 617,576 $ 58,014 Total Portfolio 26,592 $ 1,478,371 $ 2,956,079 $ 3,171,170 $ 1,341,615 $ 6,127,249 $ 7,468,864 $ (2,455,505 ) $ 5,013,359 $ 3,646,093 (1) Date we acquired the apartment community or first consolidated the partnership that owns the community. (2) Includes costs capitalized since acquisition or date of initial consolidation of the community. (3) The aggregate cost of land and depreciable property for federal income tax purposes was (4) Depreciable life for buildings and improvements ranges from 5 to 30 years and is calculated on a straight-line basis. (5) Encumbrances are presented before reduction for debt issuance costs. (6) The current carrying value of the apartment community reflects an impairment loss recognized. (7) Other includes apartment communities under development, land parcels, and certain non-residential properties held for future development. APARTMENT INCOME REIT CORP. AIMCO PROPERTIES, L.P. SCHEDULE III: REAL ESTATE AND ACCUMULATED DEPRECIATION For the Years Ended December 31, 2020, 2019, and 2018 (In Thousands) 2020 2019 2018 Total real estate balance at beginning of year $ 7,351,979 $ 7,338,906 $ 7,488,019 Additions during the year: Acquisitions 6,062 81,344 501,009 Capital additions 329,156 368,133 310,452 Dispositions and other (218,333 ) (436,404 ) (960,574 ) Total real estate balance at end of year $ 7,468,864 $ 7,351,979 $ 7,338,906 Accumulated depreciation balance at beginning of year $ 2,268,839 $ 2,228,533 $ 2,504,193 Depreciation 310,400 308,905 320,664 Dispositions and other (123,734 ) (268,599 ) (596,324 ) Accumulated depreciation balance at end of year $ 2,455,505 $ 2,268,839 $ 2,228,533

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Principles of Consolidation	Principles of Consolidation We consolidate a variable interest entity (“VIE”), in which we are considered the primary beneficiary. The primary beneficiary is the entity that has (i) the power to direct the activities that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses of the VIE or the right to receive benefits from the VIE that could be significant to the VIE. As used herein, and except where the context otherwise requires, “partnership” refers to a limited partnership or a limited liability company and “partner” refers to a partner in a limited partnership or a member of a limited liability company.
Noncontrolling Interests in the Aimco Operating Partnership	Noncontrolling Interests in the AIR Operating Partnership Noncontrolling interests in the AIR Operating Partnership consist of common OP Units and preferred OP Units and are reflected in AIR’s accompanying consolidated balance sheets as noncontrolling interests in AIR Operating Partnership. Holders of preferred OP Units participate in the AIR Operating Partnership’s income or loss only to the extent of their preferred distributions. Within AIR’s consolidated financial statements, after provision for preferred OP Unit distributions, the AIR Operating Partnership’s income or loss is allocated to the holders of common OP Units based on the weighted-average number of common OP Units (including those held by AIR) outstanding during the period. During the years ended December 31, 2020, 2019, and 2018, the holders of common OP Units had a weighted-average economic ownership interest in the AIR Operating Partnership of 5.07%, 5.20%, and 5.31%, respectively. Please refer to Note 9 for further information regarding the items comprising noncontrolling interests in the AIR Operating Partnership. Substantially all of the assets and liabilities of AIR are those of the AIR Operating Partnership.
Noncontrolling Interests in Consolidated Real Estate Partnerships	Noncontrolling Interests in Consolidated Real Estate Partnerships We generally report the unaffiliated partners’ interests in the net assets of our consolidated real estate partnerships as noncontrolling interests in consolidated real estate partnerships within consolidated equity and partners’ capital. If a real estate partnership includes redemption rights that are not within AIR and the AIR Operating Partnership’s control, the noncontrolling interest is included as temporary equity or temporary capital. If the redemption right is not currently redeemable but probable of being redeemable in the future, changes in redemption value are recognized each quarter with the change in value being reflected in additional paid-in-capital. The assets of real estate partnerships consolidated by the AIR Operating Partnership must first be used to settle the liabilities of such consolidated real estate partnerships. These consolidated real estate partnerships’ creditors do not have recourse to the general credit of the AIR Operating Partnership. Noncontrolling interests in consolidated real estate partnerships consist primarily of equity interests held by limited partners in consolidated real estate partnerships that have finite lives. We generally attribute to noncontrolling interests their share of income or loss of consolidated partnerships based on their proportionate interest in the results of operations of the partnerships, including their share of losses even if such attribution results in a deficit noncontrolling interest balance within our equity and partners’ capital accounts. The terms of the related partnership agreements generally require the partnerships to be liquidated following the sale of the underlying real estate. As the general partner in these partnerships, we ordinarily control the execution of real estate sales and other events that could lead to the liquidation, redemption or other settlement of noncontrolling interests. Changes in our ownership interest in consolidated real estate partnerships generally consist of our purchase of an additional interest in or the sale of our entire or partial interest in a consolidated real estate partnership. The effect on our equity and partners’ capital of our purchase of additional interests in consolidated real estate partnerships during the years ended December 31, 2020, 2019, and 2018, is shown in our consolidated statements of equity and partners’ capital. The effect on our equity and partners’ capital of sales of consolidated real estate or sales of our entire interest in consolidated real estate partnerships is reflected in our consolidated financial statements as gains or losses on dispositions of real estate and accordingly the effect on our equity and partners’ capital is reflected within the amount of net income allocated to us and to noncontrolling interests. Upon our deconsolidation of a real estate partnership following the sale of our partnership interests or liquidation of the partnership following sale of the related apartment community, we derecognize any remaining noncontrolling interest of the associated partnership previously recorded in our consolidated balance sheets.
Investments	Investments in Unconsolidated Real Estate Partnerships We may own general and limited partner interests in partnerships that either directly, or through interests in other real estate partnerships, own apartment communities. We generally account for investments in real estate partnerships that we do not consolidate under the equity method. Under the equity method, we recognize our share of the earnings or losses of the entity for the periods presented, inclusive of our share of any impairments and disposition gains or losses recognized by and related to such entities, and we present such amounts within income from unconsolidated real estate partnerships in our consolidated statements of operations. Investments in unconsolidated real estate partnerships are reviewed for impairments whenever events or changes in circumstances indicate that the carrying amount of the investment may not be recoverable. An impairment loss is recorded when there is a decline in the fair value below the carrying value and we conclude such decline is other-than-temporary. An impairment loss is measured based on the excess of the carrying amount of an investment over its estimated fair value. We determine the fair value of investments in unconsolidated real estate partnerships using valuation techniques that consider the terms of the in-place leases, current market data for comparable leases, our experience in leasing similar communities, and current plans. We recognized no such impairments for any of the years ended December 31, 2020 , 2019 , and 2018 The excess of our cost of the acquired partnership interests over our share of the partners’ equity or deficit is generally ascribed to the fair values of land and buildings owned by the partnerships. We amortize the excess cost ascribed to the buildings over the related estimated useful lives. Such amortization is recorded as an adjustment of the amounts of earnings or losses we recognize from such unconsolidated real estate partnerships. We may also originate loans for real estate acquisitions or developments where we either expect, or have the opportunity, to participate in the residual profits from such projects. When the risks and rewards of these arrangements are similar to an equity investor or joint venture partner, we account for these arrangements as real estate investments using the equity method of accounting. We recognize as income changes in our share of net assets, adjusted for any basis differential, in mezzanine investment income, net, in our consolidated statements of operations. In connection with the Separation, Aimco was allocated economic ownership of the mezzanine loan investment and option to acquire a 30% equity interest in the partnership owning Parkmerced Apartments. Subsequent to the Separation, all risks and rewards of ownership are Aimco’s. As of December 31, 2020, the investment in Parkmerced is included in other assets in AIR’s consolidated balance sheets, as title has not been legally transferred. Since AIR has legally assigned all risks and rewards of ownership to Aimco, there is an equal, and offsetting liability included in accrued liabilities and other in AIR’s consolidated balance sheets. Accordingly, there is no net effect on AIR’s shareholders’ equity . Investments in Securitization Trust that holds AIR Property Debt We hold investments in a securitization trust that primarily holds certain of our property debt. These investments were initially recognized at their purchase price and the discount to the face value is being accreted into interest income over the expected term of the securities. We have designated these investments as available for sale (“AFS”) debt securities, and we measure these investments at fair value with changes in their fair value, other than the changes attributed to the accretion described above, recognized as an adjustment of accumulated other comprehensive income or loss within equity and partners’ capital. Please refer to Note 13 for further information regarding these debt securities.
Real Estate	Real Estate Acquisitions Upon the acquisition of real estate, we determine whether the purchase qualifies as an asset acquisition or, less frequently, meets the definition of an acquisition of a business. We generally recognize the acquisition of apartment communities or interests in partnerships that own communities at our cost, including the related transaction costs, as asset acquisitions. We allocate the cost of apartment communities acquired based on the relative fair value of the assets acquired and liabilities assumed. The fair value of these assets and liabilities is determined using valuation techniques that rely on Level 2 and Level 3 inputs within the fair value framework. We determine the fair value of tangible assets, such as land, buildings, furniture, fixtures and equipment using valuation techniques that consider comparable market transactions, replacement costs and other available information. We determine the fair value of identified intangible assets or liabilities, which typically relate to in-place leases, using valuation techniques that consider the terms of the in-place leases, current market data for comparable leases and our experience in leasing similar communities. The intangible assets or liabilities related to in-place leases are comprised of: (a) the value of the above- and below-market leases in-place, measured over the period, including probable lease renewals for below-market leases, that the leases are expected to remain in effect; (b) the estimated unamortized portion of avoided leasing commissions and other costs that Capital Additions We capitalize costs, including certain indirect costs, incurred in connection with our capital additions activities, including redevelopments, developments, other tangible apartment community improvements, and replacements of existing apartment community components. Included in these capitalized costs are payroll costs associated with time spent by our teammates in connection with capital additions activities at the apartment community level. We characterize as “indirect costs” an allocation of certain department costs, including payroll, at the area operations and corporate levels that clearly relate to capital additions activities. We also capitalize interest, property taxes, and insurance during periods in which construction projects are in progress. We begin capitalization of costs, including certain indirect costs, incurred in connection with our capital addition activities, upon commencement of activities necessary to ready apartment communities for their intended use. These activities include when apartment communities or apartment homes are undergoing physical construction, as well as when homes are held vacant in advance of planned construction, provided that other activities such as permitting, planning and design are in progress. We cease the capitalization of costs when the apartment communities are substantially complete and ready for their intended use, which is typically when construction has been substantially completed and apartment homes are available for occupancy. Costs, including ordinary repairs, maintenance, and resident turnover costs, are charged to property operating expense as incurred. For the years ended December 31, 2020, 2019, and 2018, we capitalized to buildings and improvements $13.7 million, $11.6 million, and $7.3 million of interest costs, respectively, and $33.0 million, $36.4 million, and $35.9 million of other direct and indirect costs, respectively. Gain or Loss on Dispositions For sales of real estate, we evaluate whether the disposition has a major effect on our operations and financial results and qualify as a strategic shift. If the disposition represents a strategic shift, it is classified as discontinued operations in our consolidated financial statements for all periods presented. If the disposition does not represent a strategic shift, it is presented in continuing operations in our consolidated financial statements. Gain or loss on real estate dispositions are recognized when we no longer hold a controlling financial interest in the real estate and sufficient consideration has been received. Upon disposition, the related assets and liabilities are derecognized, and the gain or loss on disposition is recognized as the difference between the carrying amount of those assets and liabilities and the value of consideration received. Impairment Real estate and other long-lived assets to be held and used are individually evaluated for impairment when conditions exist that may indicate the carrying amount of a long-lived asset may not be recoverable. Impairment indicators include significant fluctuations in rental and other property revenues less property operating expenses, occupancy changes, significant near-term lease expirations, current and historical cash flow losses, rental rates, and if applicable, a comparison of an asset’s carrying value to its gross asset value, a measure representative of the estimated fair value of an asset. Upon determination that an impairment has occurred, we recognize an impairment loss to the extent the carrying amount exceeds the estimated fair value of the community. During the fourth quarter of 2020, we evaluated the expected hold period of a real estate asset in our Other Real Estate reporting segment. We acquired the property in 2004 for $51 million. The initial purchase price allocated to land and building totaled $81 million, which included the recording of a below market lease liability and a mark-to-market adjustment associated with assumed debt. Based on an expected shortened hold period, we reduced the carrying value of the asset to its estimated fair value of December 31, 2020 and recognized a non-cash impairment loss on real estate of The measurement of the impairment loss is based on the fair value of the communities and incorporates various estimates and assumptions, the most significant being market rental rates, operating expense assumptions, and capitalization rate. We project future rental revenue growth rates using forecasted rates from third-party market research analytics. Property expense growth rates and capitalization rate are based on the apartment communities’ historical, current, and expected future operating results, existing operating expense assumptions, and operational strategies. These projections are adjusted to reflect current economic conditions and require considerable management judgement.
Cash Equivalents	Cash Equivalents We classify highly liquid investments with an original maturity of three months or less as cash equivalents. We maintain cash equivalents in financial institutions in excess of insured limits. We have not experienced any losses in these accounts in the past and believe that we are not exposed to significant credit risk because our accounts are deposited with major financial institutions. Restricted Cash Restricted cash includes capital replacement reserves, completion repair reserves, bond sinking fund amounts, real estate tax and insurance escrow accounts held by lenders and resident security deposits.
Goodwill	Goodwill As of December 31, 2020 $32.3
Other Assets	Other Assets As of December 31, 2020 and 2019, other assets was comprised of the following amounts (in thousands): 2020 2019 Mezzanine investment $ 307,362 $ 280,258 Investments in securitization trust 100,151 94,251 Right of use lease assets 56,783 61,911 Intangible assets, net 4,438 5,716 Notes receivable, net 894 4,715 Software, equipment, and leasehold improvements 6,531 25,750 Accounts receivable, net 21,458 18,668 Prepaid expenses, real estate taxes and insurance 10,970 10,831 Deferred tax asset, net (Note 11) — 80,516 Deferred costs, deposits and other 67,439 21,977 Total other assets $ 576,026 $ 604,593
Note Receivable	Notes Receivable from Aimco In connection with the Separation, we acquired $534 million in notes receivable pledged by a subsidiary of the Spinnee that has an interest in a portfolio of assets. Our notes receivable is subordinate to the existing debt of $215.4 million as of December 31, 2020, on the portfolio of assets. The notes receivable mature on January 31, 2024, and bear interest at a rate of 5.2% per annum, payable quarterly on January 1, April 1, July 1, and October 1, commencing on April 1, 2021. The notes receivable contain certain representations, warranties, covenants and events of default, and are secured by a pool of properties owned by Aimco. Notes receivable are reported in our consolidated balance sheet at the outstanding principal balance. Interest receivable related to the unpaid principal is recorded separately from the outstanding balance in other assets in our consolidated balance sheets.
Deferred Costs	Deferred Costs We defer, as debt issuance costs, lender fees and other direct costs incurred in obtaining new financing and amortize the amounts over the terms of the related loan agreements. In connection with the modification of existing financing arrangements, we defer lender fees and amortize these costs and any unamortized debt issuance costs over the term of the modified loan agreement. Debt issuance costs associated with our revolving credit facility are included in other assets in our consolidated balance sheets. Debt issuance costs associated with non-recourse property debt and our term loan are presented as a direct deduction from the related liabilities in our consolidated balance sheets. When financing arrangements are repaid or otherwise extinguished prior to maturity, unamortized debt issuance costs are written off, additionally, any lender fees or other costs incurred in connection with the extinguishment are recognized as expense. Amortization and write-off of debt issuance costs and other extinguishment costs are included in interest expense in our consolidated statements of operations. We defer leasing costs incremental to a lease that we would not have incurred if the contract had not been obtained. Amortization of these costs is included in depreciation and amortization in our consolidated statements of operations.
Revenue from Leases	Revenue from Leases We are a lessor primarily for residential leases. Our operating leases with residents may also provide that the resident reimburse us for certain costs, primarily the resident’s share of utilities expenses, incurred by the apartment community. These reimbursements represent revenue attributable to nonlease components for which the timing and pattern of recognition is the same as the revenue for the lease components. In 2019, we adopted the practical expedient that allows us to account for the lease and nonlease components as a single component. Reimbursement and related expense are presented on a gross basis in our consolidated statements of operations, with the reimbursement included in rental and other property revenues attributable to real estate in our consolidated statements of operations. We recognize rental revenue attributed to lease components, net of any concessions, on a straight-line basis over the term of the lease.
Asset Management Business	Asset Management Business Prior to the July 2018 sale of our Asset Management business, we provided asset management and other services to certain consolidated partnerships owning apartment communities that qualify for low-income housing tax credits and are structured to provide for the pass-through of tax credits and tax deductions to their partners. We consolidated those low-income housing tax credit partnerships in which we were the sole general partner and decision maker of the partnerships. We recognized income from asset management and other services when the related fees were earned and realized or realizable.
Depreciation and Amortization	Depreciation and Amortization Depreciation for all tangible assets is calculated using the straight-line method over their estimated useful lives. Acquired buildings and improvements are depreciated over a useful life based on the age, condition, and other physical characteristics of the asset. Furniture, fixtures, and equipment are generally depreciated over five years. We depreciate capitalized costs using the straight-line method over the estimated useful life of the related improvement, which is generally 5, 15, or 30 years. We also capitalize payroll and other indirect costs incurred in connection with preparing an asset for its intended used. These costs include corporate-level costs that clearly relate to the capital addition activities, which we allocate to the applicable assets. All capitalized payroll costs and indirect costs are allocated to capital additions proportionately based on direct costs and depreciated over the estimated useful lives of such capital additions. Purchased software and other costs related to software purchased or developed for internal use are capitalized during the application development stage and are amortized using the straight-line method over the estimated useful life of the software, generally three to five years. Purchased equipment is recognized at cost and depreciated using the straight-line method over the estimated useful life of the asset, which is generally five years. Leasehold improvements are also recorded at cost and depreciated on a straight-line basis over the shorter of the asset’s estimated useful life or the term of the related lease. Certain homogeneous items that are purchased in bulk on a recurring basis, such as appliances, are depreciated using group methods that reflect the average estimated useful life of the items in each group. Except in the case of apartment community casualties, where the net book value of the lost asset is written off in the determination of casualty gains or losses, we generally do not recognize any loss in connection with the replacement of an existing apartment community component because normal replacements are considered in determining the estimated useful lives used in connection with our composite and group depreciation methods.
Insurance	Insurance We believe our insurance coverages insure our apartment communities adequately against the risk of loss attributable to fire, earthquake, hurricane, tornado, flood, and other perils. In addition, we have third-party insurance coverage (after self-insured retentions) that defray the costs of large workers’ compensation, health, and general liability exposures. We accrue losses based upon our estimates of the aggregate liability for uninsured losses incurred using certain actuarial assumptions followed in the insurance industry and based on our experience.
Share-Based Compensation	Share-Based Compensation We issue various forms of share-based compensation, including stock options and restricted stock awards with service conditions and/or market conditions. We recognize share-based employee compensation based on the fair value on the grant date and recognize compensation cost over the awards’ requisite service periods. We reduce compensation cost related to forfeited awards in the period of forfeiture. Please refer to Note 10 for further discussion of our share-based compensation.
Income Taxes	Income Taxes AIR has elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the “Code”), commencing with its taxable year ended December 31, 2020, and it intends to continue to operate in such a manner. AIR’s Predecessor also elected to be taxed as a REIT under the Code. AIR’s current and continuing qualification as a REIT depends on its ability to meet the various requirements imposed by the Internal Revenue Code, which are related to organizational structure, distribution levels, diversity of stock ownership and certain restrictions with regard to owned assets and categories of income. If AIR qualifies for taxation as a REIT, it will generally not be subject to United States federal corporate income tax on its taxable income that is currently distributed to stockholders. This treatment substantially eliminates the “double taxation” (at the corporate and stockholder levels) that generally results from an investment in a corporation. Even if AIR qualifies as a REIT, it may be subject to United States federal income and excise taxes in various situations, such as on undistributed income. AIR could also be subject to a 100% tax on transactions between it and a TRS (described below) that are determined to be non-arm’s length and on any net income from sales of apartment communities that are determined to be dealer-type prohibited transactions. The state and local tax laws may not conform to the United States federal income tax treatment, and AIR may be subject to state or local taxation in various state or local jurisdictions, including those in which we transact business. Any taxes imposed on us reduce our operating cash flow and net income. Certain of AIR’s operations, or a portion thereof, including property management and risk management, are conducted through taxable REIT subsidiaries, which are subsidiaries of the AIR Operating Partnership, and each of which we refer to as a TRS. A TRS is a subsidiary C-corporation that has not elected REIT status and, as such, is subject to United States federal corporate income tax. We use TRS entities to facilitate our ability to offer certain services and activities to our residents and investment partners that cannot be offered directly by a REIT. We also use TRS entities to hold investments in certain apartment communities. For our TRS entities, deferred income taxes result from temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for United States federal income tax purposes, and are measured using the enacted tax rates and laws that are expected to be in effect when the differences reverse. We reduce deferred tax assets by recording a valuation allowance when we determine, based on available evidence, that it is more likely than not that the assets will not be realized. We recognize the tax consequences associated with intercompany transfers between the AIR Operating Partnership and TRS entities when such transactions occur. Please refer to Note 11 for further information about our income taxes.
Earnings Per Share and Unit	Earnings per Share and Unit AIR and the AIR Operating Partnership calculate earnings per share and unit based on the weighted-average number of shares of Common Stock or common OP units, participating securities, common stock or common unit equivalents and dilutive convertible securities outstanding during the period. The AIR Operating Partnership considers both common OP units and equivalents, which have identical rights to distributions and undistributed earnings, to be common units for purposes of the earnings per unit computations. Please refer to Note 12 for further information regarding earnings per share and unit computations.
Use of Estimates	Use of Estimates The preparation of our consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts included in the financial statements and accompanying notes thereto. Actual results could differ from those estimates.
Reclassifications and Revisions	Reclassifications and Revisions On November 30, 2020, AIR’s Predecessor and the Aimco Operating Partnership effected a reverse split of Common Stock and common partnership units, respectively, at a ratio of one share or unit for every 1.23821 shares or units outstanding on the date of effectiveness. The accounting guidance for recapitalization events requires that we revise AIR’s equity and the AIR Operating Partnership’s partners’ capital as if the reverse split had occurred at the beginning of the earliest period presented. As such, we have revised the outstanding share and unit counts, presentation of share and unit activity, and earnings per share and unit, as if the reverse split had occurred on December 31, 2017. As previously stated in Note 1, the financial results prior to the Separation on December 15, 2020, include the financial results of AIR’s Predecessor, and the financial results attributable to the apartment communities retained by Aimco in the Separation are presented as discontinued operations.
Accounting Pronouncements Adopted in the Current Year	Accounting Pronouncements Adopted in the Current Year On January 1, 2020, we adopted ASC 326, Financial Instruments – Credit Losses
Recent Accounting Pronouncements	Recent Accounting Pronouncements On January 16, 2020, the FASB issued an Accounting Standards Update that addresses accounting for the transition into and out of the equity method and provides clarification of the interaction of rules for equity securities, the equity method of accounting, and forward contracts and purchase options on certain types of securities, which is effective for us on January 1, 2021. Adoption of the standards requires changes to be made prospectively and early adoption is permitted. The adoption of this standard on January 1, 2021 did not result in a change in our accounting. ted. Our preferred OP units are subject to the new standard, which will require us to include our preferred OP units in the calculation of dilutive securities. The adoption of this standard on January 1, 2021 , did not have an impact to our consolidated financial statements.

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Fair Value of Financial Instruments	Recurring Fair Value Measurements that holds certain of our property debt, which

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Summary of Other Assets	As of December 31, 2020 and 2019, other assets was comprised of the following amounts (in thousands): 2020 2019 Mezzanine investment $ 307,362 $ 280,258 Investments in securitization trust 100,151 94,251 Right of use lease assets 56,783 61,911 Intangible assets, net 4,438 5,716 Notes receivable, net 894 4,715 Software, equipment, and leasehold improvements 6,531 25,750 Accounts receivable, net 21,458 18,668 Prepaid expenses, real estate taxes and insurance 10,970 10,831 Deferred tax asset, net (Note 11) — 80,516 Deferred costs, deposits and other 67,439 21,977 Total other assets $ 576,026 $ 604,593

Significant Transactions (Table

Significant Transactions (Tables)	12 Months Ended
	Dec. 31, 2020
Significant Transactions [Abstract]
Summary of Apartment Community Sold	Sold apartment communities during the years ended December 31, 2020, 2019, and 2018, are summarized below (dollars in thousands): 2020 2019 2018 Number of apartment communities sold 2 12 4 Number of apartment homes sold 485 3,596 1,334 Gain on dispositions of real estate (1) $ 119,215 $ 503,168 $ 175,213 (1) During the year ended December 31, 2019, gain on dispositions of real estate includes the gain recognized upon the expiration of indemnification liabilities related to the sale of our Asset Management business. Major assets and liabilities related to discontinued operations at December 31, 2019 are shown below (in thousands): 2019 ASSETS: Net real estate $ 936,168 Cash and cash equivalents 6,443 Restricted cash 4,717 Investment in unconsolidated real estate partnerships 12,741 Other assets 62,627 Total assets of discontinued operations $ 1,022,696 LIABILITIES: Non-recourse property debt, net $ 492,785 Deferred tax liability 144,033 Accrued liabilities and other 26,571 Total liabilities of discontinued operations $ 663,389 Summarized results of discontinued operations for the years ended December 31, 2020, 2019, and 2018 are shown below (in thousands): 2020 2019 2018 REVENUES: Rental and other property revenues $ 144,757 $ 143,692 $ 132,163 OPERATING EXPENSES: Property operating expenses 51,710 49,502 45,372 Depreciation and amortization 72,729 62,887 48,392 Other expenses (income), net 1,897 257 (1,208 ) Total operating expenses 126,336 112,646 92,556 Interest income 2,076 2,125 1,592 Interest expense (17,972 ) (17,918 ) (20,829 ) Income from unconsolidated real estate partnerships 764 802 940 Income before income tax benefit (expense) 3,289 16,055 21,310 Income tax benefit (expense) 7,939 3,440 (319 ) Income from discontinued operations, net of tax 11,228 19,495 20,991 Net loss (income) attributable to noncontrolling interests in consolidated real estate partnerships 404 189 (5 ) Net income from discontinued operations attributable to AIR $ 11,632 $ 19,684 $ 20,986

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2020
Discontinued Operations And Disposal Groups [Abstract]
Summary of Apartment Community Sold	Sold apartment communities during the years ended December 31, 2020, 2019, and 2018, are summarized below (dollars in thousands): 2020 2019 2018 Number of apartment communities sold 2 12 4 Number of apartment homes sold 485 3,596 1,334 Gain on dispositions of real estate (1) $ 119,215 $ 503,168 $ 175,213 (1) During the year ended December 31, 2019, gain on dispositions of real estate includes the gain recognized upon the expiration of indemnification liabilities related to the sale of our Asset Management business. Major assets and liabilities related to discontinued operations at December 31, 2019 are shown below (in thousands): 2019 ASSETS: Net real estate $ 936,168 Cash and cash equivalents 6,443 Restricted cash 4,717 Investment in unconsolidated real estate partnerships 12,741 Other assets 62,627 Total assets of discontinued operations $ 1,022,696 LIABILITIES: Non-recourse property debt, net $ 492,785 Deferred tax liability 144,033 Accrued liabilities and other 26,571 Total liabilities of discontinued operations $ 663,389 Summarized results of discontinued operations for the years ended December 31, 2020, 2019, and 2018 are shown below (in thousands): 2020 2019 2018 REVENUES: Rental and other property revenues $ 144,757 $ 143,692 $ 132,163 OPERATING EXPENSES: Property operating expenses 51,710 49,502 45,372 Depreciation and amortization 72,729 62,887 48,392 Other expenses (income), net 1,897 257 (1,208 ) Total operating expenses 126,336 112,646 92,556 Interest income 2,076 2,125 1,592 Interest expense (17,972 ) (17,918 ) (20,829 ) Income from unconsolidated real estate partnerships 764 802 940 Income before income tax benefit (expense) 3,289 16,055 21,310 Income tax benefit (expense) 7,939 3,440 (319 ) Income from discontinued operations, net of tax 11,228 19,495 20,991 Net loss (income) attributable to noncontrolling interests in consolidated real estate partnerships 404 189 (5 ) Net income from discontinued operations attributable to AIR $ 11,632 $ 19,684 $ 20,986

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Lease Income for Operating Leases	The majority of lease payments we receive from our residents and tenants are fixed. We receive variable payments from our residents and commercial tenants primarily for utility reimbursements. Our total lease income, included in continuing operations, was comprised of the following amounts for all operating leases for the year ended December 31, 2020 (in thousands): 2020 2019 Fixed lease income $ 677,060 $ 722,146 Variable lease income 43,588 46,494 Straight-line rent write-off (1) (2,850 ) — Total lease income $ 717,798 $ 768,640 year ended December 31, 2020
Future Minimum Annual Rental Payments Receivable Under Residential and Commercial Leases	Future minimum annual rental payments we are contractually obligated to receive under commercial leases, excluding such extension options, are as follows as of December 31, 2020 (in thousands): 2021 $ 13,184 2022 13,488 2023 12,584 2024 11,170 2025 9,513 Thereafter 47,476 Total $ 107,415
Minimum Annual Rental Payments Under these Operating Leases	Minimum annual rental payments under these operating leases, reconciled to the lease liability included in accrued liabilities and other in our consolidated balance sheets, are as follows (in thousands): Operating Lease Future Minimum Rent 2021 $ 4,548 2022 4,280 2023 3,727 2024 3,749 2025 3,770 Thereafter 421,228 Total $ 441,302 Less: Discount (385,933 ) Total lease liability $ 55,369

Non-Recourse Property Debt an_2

Non-Recourse Property Debt and Credit Agreement (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Summary of Non-Recourse Property Loans Payable Related to Properties	The following table summarizes non-recourse property debt as of December 31, 2020 and 2019 (dollars in thousands): Outstanding Balance as of December 31, Latest Maturity Date Interest Rate Range Weighted-Average Interest Rate 2020 2019 Fixed-rate property debt January 1, 2055 2.42% to 6.01% 3.55% $ 3,631,588 $ 3,740,648 Variable-rate property debt July 13, 2033 1.09% to 1.15% 1.12% 14,505 14,505 Total non-recourse property debt 3,646,093 3,755,153 Debt issuance costs, net of accumulated amortization (17,857 ) (17,348 ) Non-recourse property debt, net $ 3,628,236 $ 3,737,805
Scheduled Principal Amortization and Maturity Payments for Non-Recourse Property Debt	As of December 31, 2020, the scheduled principal amortization and maturity payments for the non-recourse property debt were as follows (in thousands): Amortization Maturities Total 2021 $ 67,922 $ 35,848 $ 103,770 2022 68,836 201,264 270,100 2023 63,939 160,670 224,609 2024 63,112 154,685 217,797 2025 57,883 355,013 412,896 Thereafter 322,412 2,094,509 2,416,921 Total $ 644,104 $ 3,001,989 $ 3,646,093 Credit Agreement

Partners' Capital (Tables)

Partners' Capital (Tables)	12 Months Ended
	Dec. 31, 2020
Partners Capital [Abstract]
Classes of Preferred OP Units	As of December 31, 2020 and 2019, the AIR Operating Partnership had the following classes of preferred OP Units (stated at their redemption values, in thousands, except unit and per unit data): Distributions per Annum Units Issued and Outstanding Redemption Values Class of Preferred Units Percent Per Unit 2020 2019 2020 2019 Class One 8.75 % $ 8.00 90,000 90,000 $ 8,229 $ 8,229 Class Two 1.92 % $ 0.48 11,122 11,122 278 278 Class Three 7.88 % $ 1.97 1,313,927 1,338,524 32,848 33,463 Class Four 8.00 % $ 2.00 644,954 644,954 16,124 16,124 Class Six 8.50 % $ 2.13 773,693 773,693 19,342 19,342 Class Seven 7.87 % $ 1.97 26,150 26,150 654 654 Class Nine 6.00 % $ 1.50 78,956 78,956 1,974 1,974 Class Ten 6.00 % $ 1.50 — 680,000 — 17,000 Total 2,938,802 3,643,399 $ 79,449 $ 97,064
Reconciliation of Preferred OP Units	The following table presents a reconciliation of the AIR Operating Partnership’s preferred OP Units during the year ended December 31, 2020 (in thousands): 2020 Balance at January 1 $ 97,064 Preferred distributions (7,019 ) Redemption of preferred units and other (17,615 ) Net income 7,019 Balance at December 31 $ 79,449

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Total Compensation Cost Recognized for Share-Based Awards	Total compensation cost recognized for share-based awards was as follows for the years ended December 31, 2020, 2019, and 2018 (in thousands): 2020 2019 2018 Share-based compensation expense (1) $ 8,295 $ 8,146 $ 8,550 Capitalized share-based compensation (2) 946 962 1,215 Total share-based compensation (3) $ 9,241 $ 9,108 $ 9,765 (1) Amounts are recorded in general and administrative expenses on the consolidated statements of operations. (2) Amounts are recorded in building and improvements on the consolidated balance sheets. (3) Amounts are recorded in additional paid-in capital and common noncontrolling interests in the AIR Operating Partnership on the AIR consolidated balance sheets, and in general partner and special limited partner and limited partners on the AIR Operating Partnership consolidated balance sheets.
Assumptions Used in Determination of Grant-Date Fair Value of Awards	The valuation assumptions for the 2020, 2019, and 2018 grants were as follows: 2020 2019 2018 Grant date market value of a common share $ 53.26 $ 49.24 $ 40.95 Risk-free interest rate 1.48% - 1.58% 2.59% - 2.66% 2.32% - 2.68% Dividend yield 2.93 % 3.09 % 3.52 % Expected volatility 15.82% - 16.84% 19.08% - 19.24% 17.64% - 18.02% Derived vesting period of TSR Restricted Stock and TSR LTIP I units 3.5 years 3.4 years 3.4 years Weighted average expected term of TSR Stock Options and LTIP II units 5.9 years 5.8 years 5.6 years

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Components of Deferred tax Liabilities and Assets	Significant components of our deferred tax liabilities and assets are as follows (in thousands): December 31, 2020 2019 Deferred tax liabilities: Real estate and real estate partnership basis differences $ (13 ) $ — Deferred tax assets: Real estate and real estate partnership basis differences — 17,316 Tax credit carryforwards — 53,776 Net operating, capital, and other loss carryforwards — 6,147 Accruals and expenses — 6,138 Management contracts and other — 1,905 Total deferred tax assets — 85,282 Valuation allowance — (4,766 ) Net deferred tax (liabilities) assets $ (13 ) $ 80,516
Reconciliation of Unrecognized Tax Benefits	A reconciliation of the beginning and ending balance of our unrecognized tax benefits is presented below (in thousands): 2020 2019 2018 Balance at January 1 $ 5,080 $ 2,618 $ 2,476 Additions based on tax position taken in current year (1) (4,625 ) 2,758 — Additions based on tax positions related to prior years (218 ) 226 142 Reductions as a result of a lapse of the applicable statutes 4,203 (522 ) — Balance at December 31 $ 4,440 $ 5,080 $ 2,618 (1) Reduction in unrecognized tax benefit for the year ended December 31, 2020, is related to tax positions taken as a result of the Separation.
Components of Income Tax Benefit or Expense	Significant components of the income tax benefit or expense are as follows and are classified within income tax benefit in our consolidated statements of operations for the years ended December 31, 2020, 2019, and 2018 (in thousands): 2020 2019 2018 Current: Federal $ 6,271 $ 5,204 $ 11,269 State 8,637 8,558 10,218 Total current 14,908 13,762 21,487 Deferred: Federal (7,691 ) (8,575 ) (29,243 ) State (2,694 ) (4,882 ) (5,590 ) Revaluation of deferred taxes due to change in tax rate 90,914 — — Total deferred 80,529 (13,457 ) (34,833 ) Total expense (benefit) $ 95,437 $ 305 $ (13,346 )
Reconciliation of Income Tax Attributable to Operations	The reconciliation of income tax attributable to continuing operations computed at the United States statutory rate to income tax benefit is shown below (dollars in thousands): 2020 2019 2018 Amount Percent Amount Percent Amount Percent Tax (benefit) provision at United States statutory rates on consolidated income or loss from continuing operations subject to tax $ (3,516 ) 21.0 % $ (2,836 ) 21.0 % $ 33,296 21.0 % State income tax expense, net of federal tax (benefit) expense (1,964 ) 11.7 % 3,935 (29.1 %) 11,933 7.7 % Effect of permanent differences 434 (2.6 %) (139 ) 1.0 % 302 0.2 % Tax effect of intercompany transactions (1) — — % — — % (33,250 ) (21.0 %) Tax credits (296 ) 1.8 % (667 ) 4.9 % (6,897 ) (4.4 %) Tax reform revaluation — — % — — % 288 0.2 % Decrease in valuation allowance — — % (164 ) 1.2 % (20,434 ) (12.9 %) Separation 7,596 (45.4 %) — — % — — % TRS REIT election (2) 90,914 (543.1 %) — — % — — % Other 2,269 (13.6 %) 176 (1.3 %) 1,416 0.9 % Total income tax expense (benefit) $ 95,437 (570.2 %) $ 305 (2.3 %) $ (13,346 ) (8.3 %) (1) Effective January 1, 2017, we adopted a new accounting standard applicable to intercompany asset transfers. 2018 includes the tax benefit to establish the initial deferred tax asset from the intercompany transfer of a portion of the Asset Management business between the AIR Operating Partnership and TRS entities. (2) Consistent with our simplified business structure and strategy, we have elected to treat one of our taxable subsidiaries as a REIT, resulting in the non-cash removal of deferred tax asset balances for the year ended December 31, 2020.
Schedule of Dividends Per Share Held	For the years ended December 31, 2020, 2019, and 2018, dividends per share held for the entire year were estimated to have the following tax attributes: 2020 2019 2018 (unaudited) Amount Percentage Amount Percentage Amount Percentage Ordinary income $ 2.41 6.0 % $ 0.66 20.7 % $ 0.51 33.4 % Capital gains 15.00 37.4 % 1.29 40.4 % 0.93 61.2 % Qualified dividends 0.48 1.2 % 0.66 20.7 % — — % Unrecaptured Section 1250 gain 6.74 16.8 % 0.58 18.2 % 0.08 5.4 % Return of capital 15.49 38.6 % — — % — — % Total $ 40.12 100.0 % $ 3.19 100.0 % $ 1.52 100.0 %

Earnings per Share and per Un_2

Earnings per Share and per Unit (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Reconciliations of Numerator and Denominator in Calculations of Basic and Diluted Earnings per Share and per Unit	In our consolidated statement of operations, noncontrolling interest in consolidated real estate partnerships is related to both continuing and discontinuing operations. For purposes of our earnings per share calculation, we have appropriately allocated the noncontrolling interest in consolidated real estate partnerships for all periods presented. Please refer to Note 4 for detail of noncontrolling interest in consolidated real estate partnerships associated with discontinued operations. Reconciliations of the numerator and denominator in the calculations of basic and diluted earnings per share and per unit for the years ended December 31, 2020, 2019, and 2018 are as follows (in thousands, except per share and per unit data): Year Ended December 31, 2020 Income (Numerator) Shares (Denominator) Per Share Amount Basic and Diluted Earnings per Share: Loss from continuing operations attributable to AIR $ (115,961 ) 122,446 $ (0.94 ) Income from discontinued operations attributable to AIR 11,632 122,446 0.09 Net loss attributable to AIR common stockholders $ (104,329 ) 122,446 $ (0.85 ) Diluted Earnings per Share: Effect of dilutive securities — — — Net loss attributable to AIR common stockholders $ (104,329 ) 122,446 $ (0.85 ) Year Ended December 31, 2019 Income (Numerator) Shares (Denominator) Per Share Amount Basic Earnings per Share: Income from continuing operations attributable to AIR $ 446,460 119,307 $ 3.75 Income from discontinued operations attributable to AIR 19,684 119,307 0.16 Net income attributable to AIR common stockholders $ 466,144 119,307 $ 3.91 Diluted Earnings per Share: Effect of dilutive securities — 226 (0.01 ) Net income attributable to AIR common stockholders $ 466,144 119,533 $ 3.90 Year Ended December 31, 2018 Income (Numerator) Shares (Denominator) Per Share Amount Basic Earnings per Share: Income from continuing operations attributable to AIR $ 635,611 122,097 $ 5.21 Income from discontinued operations attributable to AIR 20,986 122,097 0.17 Net income attributable to AIR common stockholders $ 656,597 122,097 $ 5.38 Diluted Earnings per Share: Effect of dilutive securities — 146 (0.01 ) Net income attributable to AIR common stockholders $ 656,597 122,243 $ 5.37 Year Ended December 31, 2020 Income (Numerator) Shares (Denominator) Per Unit Amount Basic and Diluted Earnings per unit: Loss from continuing operations attributable to the AIR Operating Partnership $ (121,399 ) 128,775 $ (0.94 ) Income from discontinued operations attributable to the AIR Operating Partnership 11,632 128,775 0.09 Net loss attributable to the AIR Operating Partnership's common unitholders $ (109,767 ) 128,775 $ (0.85 ) Diluted Earnings per unit: Effect of dilutive securities — — — Net loss attributable to the AIR Operating Partnership's common unitholders $ (109,767 ) 128,775 $ (0.85 ) Year Ended December 31, 2019 Income (Numerator) Shares (Denominator) Per Unit Amount Basic Earnings per unit: Income from continuing operations attributable to the AIR Operating Partnership $ 472,493 125,893 $ 3.75 Income from discontinued operations attributable to the AIR Operating Partnership 19,684 125,893 0.16 Net income attributable to the AIR Operating Partnership's common unitholders $ 492,177 125,893 $ 3.91 Diluted Earnings per unit: Effect of dilutive securities — 271 (0.01 ) Net income attributable to the AIR Operating Partnership's common unitholders $ 492,177 126,164 $ 3.90 Year Ended December 31, 2018 Income (Numerator) Shares (Denominator) Per Unit Amount Basic Earnings per unit: Income from continuing operations attributable to the AIR Operating Partnership $ 669,888 128,323 $ 5.22 Income from discontinued operations attributable to the AIR Operating Partnership 20,986 128,323 0.16 Net income attributable to the AIR Operating Partnership's common unitholders $ 690,874 128,323 $ 5.38 Diluted Earnings per unit: Effect of dilutive securities — 146 — Net income attributable to the AIR Operating Partnership's common unitholders $ 690,874 128,469 $ 5.38

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Summary of Fair Value for AFS Debt Securities and Derivative Instrument	The following table summarizes fair value for our AFS debt securities and interest rate option as of December 31, 2020 and 2019 (in thousands): As of December 31, 2020 2019 Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 AFS debt securities $ 100,151 $ — $ 100,151 $ — $ 94,251 $ — $ 94,251 $ — Interest rate option $ 13,177 $ — $ 13,177 $ — $ — $ — $ — $ —
Summary of Carrying Value and Fair Value of Non-recourse Property Debt	The following table summarizes carrying value and fair value of our non-recourse property debt as of December 31, 2020 and 2019 (in thousands): As of December 31, 2020 2019 Carrying Value Fair Value Carrying Value Fair Value Non-recourse property debt $ 3,646,093 $ 3,730,621 $ 3,755,153 $ 3,798,789

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Variable Interest Entities	The table below summarizes apartment community information regarding VIEs consolidated by the AIR Operating Partnership. As of December 31, 2020 2019 VIEs with interests in apartment communities 5 5 Apartment communities owned by VIEs 16 5 Apartment homes in communities owned by VIEs 5,369 2,016 Assets of the AIR Operating Partnership’s consolidated VIEs must first be used to settle the liabilities of such consolidated VIEs. These consolidated VIEs’ creditors do not have recourse to the general credit of the AIR Operating Partnership. Assets and liabilities of VIEs, excluding those of the AIR Operating Partnership and those properties that remain with the Spinnee, are summarized in the table below (in thousands): As of December 31, 2020 2019 Assets Net real estate $ 1,125,315 $ 201,425 Cash and cash equivalents $ 10,548 $ 4,153 Restricted cash $ 8,818 $ 2,047 Other assets $ 23,870 $ 18,731 Liabilities Non-recourse property debt secured by AIR communities, net $ 1,278,318 $ 175,550 Accrued liabilities and other $ 34,038 $ 23,780

Business Segments (Tables)

Business Segments (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Summary of Information for Reportable Segments	The following tables present the rental and other property revenues, property operating expenses, proportionate property net operating income, and income (loss) from continuing operations before income tax benefit (expense) of our segments on a proportionate basis, excluding amounts related to communities sold or communities included in discontinued operations for the years ended December 31, 2020, 2019, and 2018 (in thousands): Same Store Other Real Estate Proportionate and Other Adjustments (1) Corporate and Amounts Not Allocated to Segments (2) Consolidated Year ended December 31, 2020: Rental and other property revenues $ 655,853 $ 13,194 $ 44,370 $ 6,139 $ 719,556 Property operating expenses 182,967 9,319 31,555 25,195 249,036 Other operating expenses not allocated to segments (3) — — — 488,461 488,461 Total operating expenses 182,967 9,319 31,555 513,656 737,497 Proportionate property net operating income (loss) 472,886 3,875 12,815 (507,517 ) (17,941 ) Other items included in income (loss) before income tax expense (4) — — — (1,194 ) (1,194 ) Income (loss) from continuing operations before income tax expense $ 472,886 $ 3,875 $ 12,815 $ (508,711 ) $ (19,135 ) Same Store Other Real Estate Proportionate and Other Adjustments (1) Corporate and Amounts Not Allocated to Segments (2) Consolidated Year ended December 31, 2019: Rental and other property revenues $ 689,255 $ 13,731 $ 27,235 $ 40,381 $ 770,602 Property operating expenses 184,150 8,614 25,190 43,287 261,241 Other operating expenses not allocated to segments (3) — — — 383,635 383,635 Total operating expenses 184,150 8,614 25,190 426,922 644,876 Proportionate property net operating income (loss) 505,105 5,117 2,045 (386,541 ) 125,726 Other items included in income (loss) before income tax expense (4) — — — 363,111 363,111 Income (loss) from continuing operations before income tax expense $ 505,105 $ 5,117 $ 2,045 $ (23,430 ) $ 488,837 Same Store Other Real Estate Proportionate and Other Adjustments (1) Corporate and Amounts Not Allocated to Segments (2) Consolidated Year ended December 31, 2018: Rental and other property revenues $ 645,917 $ 22,368 $ 25,936 $ 146,026 $ 840,247 Property operating expenses 174,708 9,863 23,842 56,311 264,724 Other operating expenses not allocated to segments (3) — — — 399,377 399,377 Total operating expenses 174,708 9,863 23,842 455,688 664,101 Proportionate property net operating income (loss) 471,209 12,505 2,094 (309,662 ) 176,146 Other items included in income before income tax benefit (4) — — — 506,120 506,120 Income from continuing operations before income tax benefit $ 471,209 $ 12,505 $ 2,094 $ 196,458 $ 682,266 (1) Represents adjustments for the noncontrolling interests in consolidated real estate partnerships’ share of the results of consolidated communities in our segments, which are included in the related consolidated amounts, but excluded from proportionate property net operating income for our segment evaluation. Also includes the reclassification of utility reimbursements from revenues to property operating expenses for the purpose of evaluating segment results. Utility reimbursements are included in rental and other property revenues in our consolidated statements of operations prepared in accordance with GAAP. (2) Includes the operating results of apartment communities sold during the periods shown or held for sale at the end of the period, if any, and the operating results of communities owned by consolidated partnerships served by our Asset Management business prior to its sale in July 2018. Also includes property management expenses and casualty gains and losses, which are included in consolidated property operating expenses and are not part of our segment performance measure. The write-off of straight-line rent receivables, recognized due to the impact of COVID-19 and the resulting economic impact on our commercial tenants, are included in consolidated rental and property revenues and are not included in our measurement of segment performance for the year ended December 31, 2020 . (3) Includes property operating expenses of partnerships served by our Asset Management business prior to its sale in July 2018, depreciation and amortization, general and administrative expenses, and other operating expenses, which may include provision for real estate impairment loss and write-offs of deferred leasing commissions, which are not included in our measure of segment performance. (4) Includes separation costs, gain on dispositions of real estate and the Asset Management business, interest income, and interest expense.
Reconciliation of Assets from Segment to Consolidated	The assets of our segments and the consolidated assets not allocated to our segments were as follows (in thousands): December 31, 2020 December 31, 2019 Same Store $ 4,545,476 $ 4,692,491 Other Real Estate 636,296 478,839 Corporate and other assets (1) 1,047,506 715,230 Assets of discontinued operations — 1,022,696 Total consolidated assets $ 6,229,278 $ 6,909,256 (1) Includes the assets not allocated to our segments, primarily corporate assets, assets of apartment communities which were sold or classified as held for sale as of December 31, 2020, and our notes receivable from Aimco.
Capital Additions Related to Segments	For the years ended December 31, 2020, 2019, and 2018, capital additions related to our segments were as follows (in thousands): 2020 2019 2018 Same Store $ 109,461 $ 200,979 $ 218,986 Other Real Estate 219,280 162,024 71,079 Total capital additions (1) $ 328,741 $ 363,003 $ 290,065 (1) Includes amounts related to commercial properties.

Unaudited Summarized Consolid_2

Unaudited Summarized Consolidated Quarterly Information (Tables)	12 Months Ended
	Dec. 31, 2020
Schedule of Unaudited Quarterly Financial Information [Line Items]
Summarized Unaudited Consolidated Quarterly Information	AIR’s summarized unaudited consolidated quarterly information for the years ended December 31, 2020 and 2019, is provided below (in thousands, except per share amounts): Quarter 2020 First Second Third Fourth Total revenues $ 186,043 $ 181,643 $ 178,124 $ 173,746 Net income (loss) from continuing operations $ 4,911 $ 40,079 $ (27,393 ) $ (132,169 ) Net income from discontinued operations $ 4,066 $ 3,125 $ 2,578 $ 1,459 Net income (loss) attributable to AIR common stockholders $ 6,679 $ 39,212 $ (25,046 ) $ (125,174 ) Net income (loss) attributable to AIR per common share – basic $ 0.06 $ 0.33 $ (0.21 ) $ (0.96 ) Net income (loss) attributable to AIR per common share – diluted $ 0.06 $ 0.33 $ (0.21 ) $ (0.96 ) Quarter 2019 First Second Third Fourth Total revenues $ 196,447 $ 190,311 $ 192,013 $ 191,831 Net income from continuing operations $ 285,951 $ 63,818 $ 85 $ 138,678 Net income from discontinued operations $ 5,344 $ 6,178 $ 3,885 $ 4,088 Net income attributable to AIR common stockholders $ 271,568 $ 59,234 $ 2,003 $ 133,339 Net income attributable to AIR per common share – basic $ 2.33 $ 0.49 $ 0.02 $ 1.11 Net income attributable to AIR per common share – diluted $ 2.33 $ 0.49 $ 0.02 $ 1.11
AIMCO PROPERTIES, L.P. [Member]
Schedule of Unaudited Quarterly Financial Information [Line Items]
Summarized Unaudited Consolidated Quarterly Information	The AIR Operating Partnership’s summarized unaudited consolidated quarterly information for the years ended December 31, 2020 and 2019, is provided below (in thousands, except per unit amounts): Quarter 2020 First Second Third Fourth Total revenues $ 186,043 $ 181,643 $ 178,124 $ 173,746 Net income (loss) from continuing operations $ 4,911 $ 40,079 $ (27,393 ) $ (132,169 ) Net income from discontinued operations $ 4,066 $ 3,125 $ 2,578 $ 1,459 Net income (loss) attributable to the Partnership's common unitholders $ 7,047 $ 41,319 (26,387 ) $ (131,746 ) Net income (loss) attributable to the Partnership's common unitholders per common unit – basic $ 0.06 $ 0.33 $ (0.21 ) $ (0.96 ) Net income (loss) attributable to the Partnership's common unitholders per common unit – diluted $ 0.06 $ 0.33 $ (0.21 ) $ (0.96 ) Quarter 2019 First Second Third Fourth Total revenues $ 196,447 $ 190,311 $ 192,013 $ 191,831 Net income from continuing operations $ 285,951 $ 63,818 $ 85 $ 138,678 Net income from discontinued operations $ 5,344 $ 6,178 $ 3,885 $ 4,088 Net income attributable to the Partnership's common unitholders $ 286,639 $ 62,817 $ 2,138 $ 140,583 Net income attributable to the Partnership's common unitholders per common unit – basic $ 2.33 $ 0.50 $ 0.02 $ 0.90 Net income attributable to the Partnership's common unitholders per common unit – diluted $ 2.33 $ 0.50 $ 0.02 $ 0.90

Organization (Details Textual)

Organization (Details Textual)	12 Months Ended
	Dec. 31, 2020Propertyapartment_homeshares	Sep. 08, 2020apartment_homeMulti_family_apartment
Organization [Line Items]
Number of apartment communities | Multi_family_apartment		12
Number of apartment homes in apartment communities | apartment_home		4,051
Partially Owned Properties [Member]
Organization [Line Items]
Number of apartment communities | Property	99
Number of apartment homes in apartment communities | apartment_home	26,592
Percentage of average ownership of portfolio	94.00%
AIR Operating Partnership [Member]
Organization [Line Items]
Common operating partnership units and equivalents outstanding | shares	159,155,544
Common operating partnership units and equivalents outstanding | shares	148,861,036
Percentage of the Aimco Operating Partnership's common partnership units and equivalents owned by Aimco	93.50%
Percentage of economic interest	94.90%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details Textual) $ in Thousands	Nov. 30, 2020	Feb. 03, 2019	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Weighted average ownership interest			5.07%	5.20%	5.31%
Provision for real estate impairment loss			$ 47,281	$ 0	$ 0
Option to acquire equity interest in partnership, percentage			30.00%
Interest costs capitalized			$ 13,700	11,600	7,300
Other direct and indirect costs capitalized			33,000	36,400	$ 35,900
Acquisition of property			51,000
Purchase price allocation			81,000
Goodwill			32,286	32,286
Subordinated debt			$ 215,400
Estimated useful life			15 years
Percentage of income tax on income from non-arms length transactions			100.00%
Equity reverse stock split	0.0123821	0.0103119
Minimum [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life			5 years
Estimated useful life of software			3 years
Maximum [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life			30 years
Estimated useful life of software			5 years
Furniture, Fixtures and Equipment [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life			5 years
Equipment [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life			5 years
AIMCO [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Goodwill			$ 5,500	$ 5,500
Note Receivable issue from Aimco			$ 534,000
Note maturity date			Jan. 31, 2024
Note interest rate			5.20%
Note frequency of periodic payment			quarterly

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Mezzanine investment	$ 307,362	$ 280,258
Investments in securitization trust	100,151	94,251
Right of use lease assets	56,783	61,911
Intangible assets, net	4,438	5,716
Notes receivable, net	894	4,715
Software, equipment, and leasehold improvements	6,531	25,750
Accounts receivable, net	21,458	18,668
Prepaid expenses, real estate taxes and insurance	10,970	10,831
Deferred tax asset, net (Note 11)		80,516
Deferred costs, deposits and other	67,439	21,977
Total other assets	$ 576,026	$ 604,593

Significant Transactions (Detai

Significant Transactions (Details Textual) $ in Thousands		Sep. 08, 2020USD ($)apartment_homeMulti_family_apartment$ / Home	Aug. 25, 2020USD ($)	Dec. 31, 2020USD ($)Propertyapartment_home	Dec. 31, 2019USD ($)Propertyapartment_home	Dec. 31, 2018USD ($)Propertyapartment_home
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of apartment communities | Multi_family_apartment		12
Number of apartment homes in apartment communities | apartment_home		4,051
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		$ 2,400,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures | $ / Home		592,000
Secured term loan		$ 1,220,000
Implied equity value contributed by communities		1,180,000
Investment owned amount		$ 461,000
Gain on dispositions of real estate and the Asset Management business				$ 119,215	$ 503,168	$ 677,463
Wholly And Partially Owned Consolidated Properties | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of apartment communities | Property				2	12	4
Number of apartment homes in apartment communities | apartment_home				485	3,596	1,334
Payments to acquire businesses			$ 89,600
Gross proceeds from the sale of real estate						$ 590,000
Gain on dispositions of real estate and the Asset Management business	[1]			$ 119,215	$ 503,168	175,213
Net proceeds to Aimco from the sale of real estate						512,200
Wholly And Partially Owned Consolidated Properties | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Asset Management Business [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain on dispositions of real estate and the Asset Management business						500,300
Wholly And Partially Owned Consolidated Properties | Disposal Group, Disposed of by Sale, Not Discontinued Operations | La Jolla Cove [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Stated value of seller financing provided						48,600
Net cash proceeds received						$ 5,000
Ownership Exchanged
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Joint venture ownership percentage		39.00%
Ownership Retained
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Joint venture ownership percentage retained		61.00%
[1]	(1) During the year ended December 31, 2019, gain on dispositions of real estate includes the gain recognized upon the expiration of indemnification liabilities related to the sale of our Asset Management business.

Significant Transactions - Summ

Significant Transactions - Summary of Apartment Community Dispositions (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2020USD ($)Propertyapartment_home	Dec. 31, 2019USD ($)Propertyapartment_home	Dec. 31, 2018USD ($)Propertyapartment_home	Sep. 08, 2020apartment_homeMulti_family_apartment
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of apartment communities sold | Multi_family_apartment					12
Number of apartment homes sold | apartment_home					4,051
Gain on dispositions of real estate and the Asset Management business | $		$ 119,215	$ 503,168	$ 677,463
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Wholly And Partially Owned Consolidated Properties
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of apartment communities sold | Property		2	12	4
Number of apartment homes sold | apartment_home		485	3,596	1,334
Gain on dispositions of real estate and the Asset Management business | $	[1]	$ 119,215	$ 503,168	$ 175,213
[1]	(1) During the year ended December 31, 2019, gain on dispositions of real estate includes the gain recognized upon the expiration of indemnification liabilities related to the sale of our Asset Management business.

Discontinued Operations - Summa

Discontinued Operations - Summary of Major Assets and Liabilities Related To Discontinued Operations (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
ASSETS:
Net real estate	$ 5,013,359	$ 5,083,140
Cash and cash equivalents		6,443
Restricted cash	29,266	30,083
Investment in unconsolidated real estate partnerships		12,741
Other assets		62,627
Total assets of discontinued operations		1,022,696
LIABILITIES:
Non-recourse property debt, net	3,628,236	3,737,805
Deferred tax liability		144,033
Accrued liabilities and other	598,736	270,487
Total liabilities of discontinued operations	$ 0	663,389
Discontinued Operations [Member]
ASSETS:
Net real estate		936,168
Restricted cash		4,717
LIABILITIES:
Non-recourse property debt, net		492,785
Accrued liabilities and other		$ 26,571

Discontinued Operations - Sum_2

Discontinued Operations - Summarized Results of Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
REVENUES:
Rental and other property revenues									$ 144,757	$ 143,692	$ 132,163
OPERATING EXPENSES:
Depreciation and amortization									72,729	62,887	48,392
Total operating expenses									126,336	112,646	92,556
Interest income									2,076	2,125	1,592
Interest expense									(17,972)	(17,918)	(20,829)
Loss from unconsolidated real estate partnerships									0	0	(864)
Income before income tax benefit (expense)									3,289	16,055	21,310
Income tax benefit (expense)									7,939	3,440	(319)
Income from discontinued operations, net of tax	$ 1,459	$ 2,578	$ 3,125	$ 4,066	$ 4,088	$ 3,885	$ 6,178	$ 5,344	11,228	19,495	20,991
Net loss (income) attributable to noncontrolling interests in consolidated real estate partnerships									404	189	(5)
Net income from discontinued operations attributable to AIR									11,632	19,684	20,986
Discontinued Operations [Member]
OPERATING EXPENSES:
Property operating expenses									51,710	49,502	45,372
Other expenses (income), net									1,897	257	(1,208)
Loss from unconsolidated real estate partnerships									$ 764	$ 802	$ 940

Discontinued Operations - (Deta

Discontinued Operations - (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)	Jan. 01, 2021Property
Subsequent Event [Member] | Redevelopment Property [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of leased property		4
Master Service Agreement [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Master lease agreement term	18 months
Master lease agreement commencement date	Jan. 1, 2021
Master Service Agreement [Member] | Subsequent Event [Member] | Redevelopment Property [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of leased property		4
Other Expense [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Transaction costs | $	$ 57

Leases - Lease Income for Opera

Leases - Lease Income for Operating Leases (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Fixed lease income		$ 677,060	$ 722,146
Variable lease income		43,588	46,494
Straight-line rent write-off	[1]	(2,850)
Total lease income		$ 717,798	$ 768,640
[1]	We monitor the collectability of all unpaid rent amounts. The onset of COVID-19 and the anticipated economic slowdown resulted in a $2.9 million write-off of accrued straight-line rent during the year ended December 31, 2020

Leases - Lease Income for Ope_2

Leases - Lease Income for Operating Leases (Parenthetical) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Disaggregation Of Revenue [Line Items]
Write off of straight line rent receivables	$ 2,850	[1]
COVID Related Write-off [Member]
Disaggregation Of Revenue [Line Items]
Write off of straight line rent receivables	$ 2,900
[1]	We monitor the collectability of all unpaid rent amounts. The onset of COVID-19 and the anticipated economic slowdown resulted in a $2.9 million write-off of accrued straight-line rent during the year ended December 31, 2020

Leases - Future Minimum Annual

Leases - Future Minimum Annual Payments Receivable Under Residential and Commercial Leases (Details) - Commercial Real Estate [Member] $ in Thousands	Dec. 31, 2020USD ($)
Lessee Lease Description [Line Items]
2021	$ 13,184
2022	13,488
2023	12,584
2024	11,170
2025	9,513
Thereafter	47,476
Total	$ 107,415

Leases (Details Textual)

Leases (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Jan. 01, 2021USD ($)Property
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Total lease liability	$ 55,369
Commercial lease [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Lease, existence of option to extend	true
Residential Lease [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Lease, existence of option to extend	false
Weighted average remaining term	8 months 15 days
Lease, option to extend	Generally, our residential leases do not provide extension options
Redevelopment Property [Member] | Subsequent Event [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Number of leased property | Property				4
Future lease payment expected in 2021				$ 25,300
Ground and Office Leases [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Lease cost	$ 8,000
Lease cost		$ 10,700	$ 5,100
Ground Lease [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Weighted average remaining term	73 years 3 months 18 days
Operating lease, weighted average discount rate, percent	6.60%
Total lease liability	$ 44,200
Office Lease [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Weighted average remaining term	7 years 7 months 6 days
Operating lease, weighted average discount rate, percent	3.60%

Leases - Minimum Annual Rental

Leases - Minimum Annual Rental Payments Under these Operating Leases (Details) $ in Thousands	Dec. 31, 2020USD ($)
Leases [Abstract]
2021	$ 4,548
2022	4,280
2023	3,727
2024	3,749
2025	3,770
Thereafter	421,228
Total	441,302
Less: Discount	(385,933)
Total lease liability	$ 55,369
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesAndOtherLiabilities

Non-Recourse Property Debt an_3

Non-Recourse Property Debt and Credit Agreement (Details Textual)	12 Months Ended
	Dec. 31, 2020USD ($)Property	Dec. 15, 2020USD ($)	Sep. 08, 2020Multi_family_apartment	Apr. 20, 2020USD ($)	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Debt Instrument, Covenant Description	We have agreed to maintain a fixed charge coverage ratio of 1.40x, as well as other covenants customary for similar revolving credit arrangements. We expect to remain in compliance with these covenants
Number of apartment communities | Multi_family_apartment			12
Non-recourse property debt, net	$ 3,628,236,000				$ 3,737,805,000
Outstanding borrowings under the revolving credit facility	265,600,000				275,000,000
Fixed Rate Property Debt
Debt Instrument [Line Items]
Aggregate gross book value	3,700,000,000
Non-recourse property debt, net	$ 3,631,588,000				3,740,648,000
Fixed Rate Property Debt | Maximum [Member]
Debt Instrument [Line Items]
Note maturity date	Jan. 1, 2055
Fixed Rate Property Debt | Pledged as Collateral
Debt Instrument [Line Items]
Number of apartment communities | Property	57
Variable Rate Property Debt
Debt Instrument [Line Items]
Aggregate gross book value	$ 14,500,000
Non-recourse property debt, net	$ 14,505,000				14,505,000
Variable Rate Property Debt | Maximum [Member]
Debt Instrument [Line Items]
Note maturity date	Jul. 13, 2033
Variable Rate Property Debt | Pledged as Collateral
Debt Instrument [Line Items]
Number of apartment communities | Property	3
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, dividend restrictions	aggregate amount that does not exceed the greater of 95% of our funds from operations, as defined by NAREIT, for such period, subject to certain non-cash adjustments, or such amount as may be necessary to maintain AIR’s REIT status.
Fixed charge coverage ratio	1.40
Initial interest rate for credit facility	LIBOR plus 1.00%, or, at our option, a base rate plus 0.0%
Outstanding borrowings under the revolving credit facility	$ 265,600,000				$ 275,000,000
Credit facility maturity date	Jan. 22, 2022
Credit facility interest rate at period end	1.46%				3.00%
Amount outstanding for undrawn letters of credit issued under revolving credit facility	$ 23,700,000
Remaining borrowing capacity under credit facility	$ 310,700,000
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Spread on variable interest rate	1.00%
Revolving Credit Facility [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Spread on variable interest rate	0.00%
Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity of revolving credit facility		$ 800,000,000
Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity of revolving credit facility		$ 600,000
Term Loan [Member]
Debt Instrument [Line Items]
Non-recourse property debt, net				$ 350,000,000
Note maturity date	Apr. 20, 2021
Initial interest rate for credit facility	30-day LIBOR plus 1.60%, with a 50 basis point LIBOR floor
Term Loan [Member] | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Spread on variable interest rate	1.60%
Floor interest rate	0.50%

Non-Recourse Property Debt an_4

Non-Recourse Property Debt and Credit Agreement - Summary of Non-Recourse Property Loans Payable Related to Properties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Non-recourse property debt, net	$ 3,628,236	$ 3,737,805
Non-recourse property debt	3,646,093	3,755,153
Debt issuance costs, net of accumulated amortization	(17,857)	(17,348)
Fixed-rate property debt
Debt Instrument [Line Items]
Non-recourse property debt, net	$ 3,631,588	3,740,648
Weighted-Average Interest Rate	3.55%
Fixed-rate property debt | Maximum [Member]
Debt Instrument [Line Items]
Latest Maturity Date	Jan. 1, 2055
Interest Rate	6.01%
Fixed-rate property debt | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate	2.42%
Variable Rate Property Debt
Debt Instrument [Line Items]
Non-recourse property debt, net	$ 14,505	$ 14,505
Weighted-Average Interest Rate	1.12%
Variable Rate Property Debt | Maximum [Member]
Debt Instrument [Line Items]
Latest Maturity Date	Jul. 13, 2033
Interest Rate	1.15%
Variable Rate Property Debt | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate	1.09%

Non-Recourse Property Debt an_5

Non-Recourse Property Debt and Credit Agreement - Scheduled Principal Amortization and Maturity Payments for Non-Recourse Property Debt (Details) $ in Thousands	Dec. 31, 2020USD ($)
Amortization
2021	$ 67,922
2022	68,836
2023	63,939
2024	63,112
2025	57,883
Thereafter	322,412
Total	644,104
Maturities
2021	35,848
2022	201,264
2023	160,670
2024	154,685
2025	355,013
Thereafter	2,094,509
Total	3,001,989
Long Term Debt Amortization and Maturities
2021	103,770
2022	270,100
2023	224,609
2024	217,797
2025	412,896
Thereafter	2,416,921
Total	$ 3,646,093

Commitments and Contingencies (

Commitments and Contingencies (Details Textual) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2017Party	Dec. 31, 2020USD ($)
Long-term Purchase Commitment [Line Items]
Number of potentially-responsible parties | Party	4
Environmental and other liabilities		$ 17.5
Maximum [Member] | AIMCO Operating Partnership [Member]
Long-term Purchase Commitment [Line Items]
Environmental and other liabilities		17.5
Commitments related to development, redevelopment and capital improvement activities [Member]
Long-term Purchase Commitment [Line Items]
Commitments related to active redevelopments and developments		$ 18
Time Period of Long-term Purchase Commitment		24 months
Commitments related to operations [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Time Period of Long-term Purchase Commitment		1 year

AIR Equity (Details Textual)

AIR Equity (Details Textual)	Jan. 28, 2021$ / shares	Nov. 30, 2020USD ($)shares	Feb. 03, 2019USD ($)shares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / shares	Dec. 14, 2020shares
Class Of Stock [Line Items]
Common Stock, shares authorized (in shares)				1,021,175,000	500,787,260		1,021,175,000
Preferred Stock, shares authorized (in shares)							1,000,000
Dividends declared per common share (in dollars per share) | $ / shares				$ 40.12	$ 3.19	$ 1.52
Quarterly cash dividend amount (in dollars per share) | $ / shares				$ 0.82	$ 0.39
Equity reverse stock split		0.0123821	0.0103119
Classes of perpetual preferred stock
Cash dividends on common stock declared | $				$ 304,992,000	$ 241,643,000	$ 238,067,000
Preferred Stock, Liquidation Preference, Value | $				$ 100,000
Dividends per share percentage increase				8.5
Class A Cumulative Preferred Stock
Classes of perpetual preferred stock
Preferred stock, shares issued				20
Preferred stock, shares outstanding				20
Outstanding principal balance of shares issued and outstanding | $				$ 2,000,000
Preferred Stock, Par or Stated Value Per Share | $ / shares				$ 0.01
Special Dividend Paid [Member]
Classes of perpetual preferred stock
Cash dividends on common stock declared | $		$ 121,800,000	$ 67,100,000
Common shares issued in special dividend (in shares)		35,400,000	4,500,000
Special dividend, cash paid in lieu of fractional shares | $			$ 400,000
Special Dividend Paid [Member] | Subsequent Event [Member]
Class Of Stock [Line Items]
Quarterly cash dividend amount (in dollars per share) | $ / shares	$ 0.43
Common Stock
Class Of Stock [Line Items]
Dividends declared per common share (in dollars per share) | $ / shares				$ 0.41	$ 0.39	$ 0.38
Classes of perpetual preferred stock
Common shares issued in special dividend (in shares)				(28,629,000)	(3,628,000)

Partners' Capital - Classes of

Partners' Capital - Classes of Preferred OP Units (Details) - AIMCO PROPERTIES, L.P. [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Limited Partners Capital Account [Line Items]
Units issued (in shares)	2,938,802	3,643,399
Units outstanding (in shares)	2,938,802	3,643,399
Redemption values	$ 79,449	$ 97,064
Class One [Member]
Limited Partners Capital Account [Line Items]
Distributions per annum	8.75%
Distributions per annum (in dollars per share)	$ 8
Units issued (in shares)	90,000	90,000
Units outstanding (in shares)	90,000	90,000
Redemption values	$ 8,229	$ 8,229
Class Two [Member]
Limited Partners Capital Account [Line Items]
Distributions per annum	1.92%
Distributions per annum (in dollars per share)	$ 0.48
Units issued (in shares)	11,122	11,122
Units outstanding (in shares)	11,122	11,122
Redemption values	$ 278	$ 278
Class Three [Member]
Limited Partners Capital Account [Line Items]
Distributions per annum	7.88%
Distributions per annum (in dollars per share)	$ 1.97
Units issued (in shares)	1,313,927	1,338,524
Units outstanding (in shares)	1,313,927	1,338,524
Redemption values	$ 32,848	$ 33,463
Class Four [Member]
Limited Partners Capital Account [Line Items]
Distributions per annum	8.00%
Distributions per annum (in dollars per share)	$ 2
Units issued (in shares)	644,954	644,954
Units outstanding (in shares)	644,954	644,954
Redemption values	$ 16,124	$ 16,124
Class Six [Member]
Limited Partners Capital Account [Line Items]
Distributions per annum	8.50%
Distributions per annum (in dollars per share)	$ 2.13
Units issued (in shares)	773,693	773,693
Units outstanding (in shares)	773,693	773,693
Redemption values	$ 19,342	$ 19,342
Class Seven [Member]
Limited Partners Capital Account [Line Items]
Distributions per annum	7.87%
Distributions per annum (in dollars per share)	$ 1.97
Units issued (in shares)	26,150	26,150
Units outstanding (in shares)	26,150	26,150
Redemption values	$ 654	$ 654
Class Nine [Member]
Limited Partners Capital Account [Line Items]
Distributions per annum	6.00%
Distributions per annum (in dollars per share)	$ 1.50
Units issued (in shares)	78,956	78,956
Units outstanding (in shares)	78,956	78,956
Redemption values	$ 1,974	$ 1,974
Class Ten [Member]
Limited Partners Capital Account [Line Items]
Distributions per annum	6.00%
Distributions per annum (in dollars per share)	$ 1.50
Units issued (in shares)		680,000
Units outstanding (in shares)		680,000
Redemption values		$ 17,000

Partners' Capital - Narrative (

Partners' Capital - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 21, 2020	Feb. 03, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Cash dividends on common stock declared			$ 304,992	$ 241,643	$ 238,067
AIMCO PROPERTIES, L.P. [Member]
Related Party Transaction [Line Items]
Redeemable partnership preferred units redeemed for cash during period (in units)			705,000	169,000	10,000
Redeemable partnership preferred units redeemed in exchange for shares during period (in units)			0
Common OP Units redeemed in exchange for cash during period (in units)			64,000	129,000	224,000
Common OP Units redeemed in exchange for shares during period			159,000	127,000	0
Dividends declared per common share/unit (in dollars per share)			$ 0.41	$ 0.39	$ 0.38
AIMCO PROPERTIES, L.P. [Member] | Special Distribution [Member]
Related Party Transaction [Line Items]
Cash dividends on common stock declared	$ 128,700	$ 72,700
Stock dividends on common stock declared (in shares)	35,400,000	4,800,000
Special distribution, cash paid in lieu of fractional shares		$ 400

Partners' Capital - Reconciliat

Partners' Capital - Reconciliation of Preferred OP Units (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Temporary Equity [Line Items]
Balance at January 1	$ 97,064
Balance at December 31	79,449
AIMCO PROPERTIES, L.P. [Member]
Temporary Equity [Line Items]
Balance at January 1	97,064
Preferred distributions	(7,019)
Redemption of preferred units and other	(17,615)
Net income	7,019
Balance at December 31	$ 79,449

Share-Based Compensation (Detai

Share-Based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unvested compensation cost not yet recognized for options and restricted stock awards	$ 9.9
Weighted average period over which unvested compensation cost expected to be recognized	1 year 7 months 6 days
Grant period	10 years
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vest period	4 years
Term of stock options	10 years
Requisite service period	4 years
Stock option outstanding	827,853
Stock options outstanding, aggregate intrinsic value	$ 3.1
Stock options outstanding, weighted average remaining contractual term	4 years 9 months 18 days
Stock options exercisable	733,942
Stock options exercisable, aggregate intrinsic value	$ 2.9
Stock options exercisable, weighted average remaining contractual term	4 years 10 months 24 days
TSR Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
TSR restricted shares performance measurement period	3 years
Term of stock options	10 years
Options granted, weighted average grant-date fair value (dollars per share)	$ 8.15
TSR Stock Awards [Member] | NAREIT Apartment Index [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted percentage of index used to compare to TSR	60.00%
TSR Stock Awards [Member] | MSCI US REIT Index [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted percentage of index used to compare to TSR	40.00%
TSR LTIP Units [Member] | 36 Months After Grant Date [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage, TSR restricted stock	50.00%
TSR LTIP Units [Member] | 48 Months After Grant Date [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage, TSR restricted stock	50.00%
Time-Based Restricted Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vest period	4 years
Requisite service period	4 years
Number of share unvested	94,663
Weighted average grant fair value	$ 45.51
Aggregate fair value of restricted stock awards that vested	$ 7.5	$ 13.7	$ 8.4
TSR Restricted Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of share unvested	222,848
Weighted average grant fair value	$ 49.43
TSR LTIP II Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of share unvested	1,112,342
Weighted average grant fair value	$ 9.58
2020 Stock Award and Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available to be granted under plan (in shares)	3,000,000

Share-Based Compensation - Tota

Share-Based Compensation - Total Compensation Cost Recognized for Share-based Awards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-based compensation expense	$ 8,295	$ 8,146	$ 8,550
Capitalized share-based compensation	946	962	1,215
Total share-based compensation	$ 9,241	$ 9,108	$ 9,765

Share-Based Compensation - Assu

Share-Based Compensation - Assumptions Used in the Determination of Grant-Date Fair Value of Awards (Details) - TSR Stock Awards [Member] - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grant date market value of a common share	$ 53.26	$ 49.24	$ 40.95
Risk-free interest rate, minimum	1.48%	2.59%	2.32%
Risk-free interest rate, maximum	1.58%	2.66%	2.68%
Dividend yield	2.93%	3.09%	3.52%
Derived vesting period of TSR Restricted Stock and TSR LTIP I units	3 years 6 months	3 years 4 months 24 days	3 years 4 months 24 days
Weighted average expected term of TSR Stock Options and LTIP II units	5 years 10 months 24 days	5 years 9 months 18 days	5 years 7 months 6 days
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	15.82%	19.08%	17.64%
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	16.84%	19.24%	18.02%

Income Taxes (Details Textual)

Income Taxes (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Income Tax Disclosure [Abstract]
Tax rate of deferred tax assets and liabilities	0
Consolidated income (loss) subject to tax	$ (16.7)	$ (13.5)	$ 133.3

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Liabilities and Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax liabilities:
Real estate and real estate partnership basis differences	$ (13)
Deferred tax assets:
Real estate and real estate partnership basis differences		$ 17,316
Tax credit carryforwards		53,776
Net operating, capital, and other loss carryforwards		6,147
Accruals and expenses		6,138
Management contracts and other		1,905
Total deferred tax assets		85,282
Valuation allowance		(4,766)
Net deferred tax (liabilities) assets	$ (13)
Net deferred tax (liabilities) assets		$ 80,516

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of unrecognized tax benefits
Balance at January 1	$ 5,080	$ 2,618	$ 2,476
Additions based on tax position taken in current year	(4,625)	2,758
Additions based on tax positions related to prior years	(218)	226	142
Reductions as a result of a lapse of the applicable statutes	4,203	(522)
Balance at December 31	$ 4,440	$ 5,080	$ 2,618

Income Taxes - Components of In

Income Taxes - Components of Income Tax Benefit or Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
Federal	$ 6,271	$ 5,204	$ 11,269
State	8,637	8,558	10,218
Total current	14,908	13,762	21,487
Deferred:
Federal	(7,691)	(8,575)	(29,243)
State	(2,694)	(4,882)	(5,590)
Revaluation of deferred taxes due to change in tax rate	90,914	0	0
Total deferred	80,529	(13,457)	(34,833)
Total expense (benefit)	$ 95,437	$ 305	$ (13,346)

Income Taxes - Reconciliation_2

Income Taxes - Reconciliation of Income Tax Attributable to Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Amount
Tax (benefit) provision at United States statutory rates on consolidated income or loss from continuing operations subject to tax	$ (3,516)	$ (2,836)	$ 33,296
State income tax expense, net of federal tax (benefit) expense	(1,964)	3,935	11,933
Effect of permanent differences	434	(139)	302
Tax effect of intercompany transactions	0	0	(33,250)
Tax credits	(296)	(667)	(6,897)
Tax reform revaluation	0	0	288
Decrease in valuation allowance	0	(164)	(20,434)
Separation	7,596	0	0
TRS REIT election	90,914	0	0
Other	2,269	176	1,416
Total expense (benefit)	$ 95,437	$ 305	$ (13,346)
Percent
Tax (benefit) provision at United States statutory rates on consolidated income or loss from continuing operations subject to tax	21.00%	21.00%	21.00%
State income tax expense, net of federal tax (benefit) expense	11.70%	(29.10%)	7.70%
Effect of permanent differences	(2.60%)	1.00%	0.20%
Tax effect of intercompany transactions	0.00%	0.00%	(21.00%)
Tax credits	1.80%	4.90%	(4.40%)
Tax reform revaluation			0.002
Decrease in valuation allowance	0.00%	1.20%	(12.90%)
Separation	(45.40%)
TRS REIT election	(543.10%)
Other	(13.60%)	(1.30%)	0.90%
Total income tax expense (benefit)	(570.20%)	(2.30%)	(8.30%)

Income Taxes - Schedule of Divi

Income Taxes - Schedule of Dividends Per Share Held (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Amount
Ordinary income	$ 2.41	$ 0.66	$ 0.51
Capital gains	15	1.29	0.93
Qualified dividends	0.48	0.66	0
Unrecaptured Section 1250 gain	6.74	0.58	0.08
Return of capital	15.49	0	0
Total	$ 40.12	$ 3.19	$ 1.52
Percentage
Ordinary income	6.00%	20.70%	33.40%
Capital gains	37.40%	40.40%	61.20%
Qualified dividends	1.20%	20.70%	0.00%
Unrecaptured Section 1250 gain	16.80%	18.20%	5.40%
Return of capital	38.60%	0.00%	0.00%
Total	100.00%	100.00%	100.00%

Earnings per Share and per Un_3

Earnings per Share and per Unit - Reconciliations of Numerator and Denominator in Calculations of Basic and Diluted Earnings per Share and per Unit (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic and Diluted Earnings per Share:
Income (Loss) from continuing operations attributable to AIR									$ (115,961)	$ 446,460	$ 635,611
Income from discontinued operations attributable to AIR									11,632	19,684	20,986
Net (loss) income attributable to AIR common stockholders	$ (125,174)	$ (25,046)	$ 39,212	$ 6,679	$ 133,339	$ 2,003	$ 59,234	$ 271,568	$ (104,329)	$ 466,144	$ 656,597
Income (Loss) from continuing operations attributable to AIR, Shares									122,446	119,307	122,097
Income from discontinued operations attributable to AIR, Shares									122,446	119,307	122,097
Net Income (loss) attributable to AIR common stockholders, Shares									122,446	119,307	122,097
Income (Loss) from continuing operations attributable to AIR, Per share amount									$ (0.94)	$ 3.75	$ 5.21
Income from discontinued operations attributable to AIR, Per share amount									0.09	0.16	0.17
Net Income (loss) attributable to AIR common stockholders, Per share amount									$ (0.85)	$ 3.91	$ 5.38
Diluted Earnings per Share:
Net Income (loss) attributable to AIR common stockholders									$ (104,329)	$ 466,144	$ 656,597
Net Income (loss) attributable to AIR common stockholders, Shares									122,446	119,533	122,243
Effect of dilutive securities, Shares										226	146
Effect of dilutive securities, Per share amount										$ (0.01)	$ (0.01)
Net (loss) income attributable to AIR per common share – diluted	$ (0.96)	$ (0.21)	$ 0.33	$ 0.06	$ 1.11	$ 0.02	$ 0.49	$ 2.33	$ (0.85)	$ 3.90	$ 5.37
AIMCO Properties, LP [Member]
Basic and Diluted Earnings per Share:
Income (Loss) from continuing operations attributable to AIR									$ (121,399)	$ 472,493	$ 669,888
Income from discontinued operations attributable to AIR									11,632	19,684	20,986
Net (loss) income attributable to AIR common stockholders									$ (109,767)	$ 492,177	$ 690,874
Income (Loss) from continuing operations attributable to AIR, Shares									128,775	125,893	128,323
Income from discontinued operations attributable to AIR, Shares									128,775	125,893	128,323
Net Income (loss) attributable to AIR common stockholders, Shares									128,775	125,893	128,323
Income (Loss) from continuing operations attributable to AIR, Per share amount									$ (0.94)	$ 3.75	$ 5.22
Income from discontinued operations attributable to AIR, Per share amount									0.09	0.16	0.16
Net Income (loss) attributable to AIR common stockholders, Per share amount									$ (0.85)	$ 3.91	$ 5.38
Diluted Earnings per Share:
Net Income (loss) attributable to AIR common stockholders									$ (109,767)	$ 492,177	$ 690,874
Net Income (loss) attributable to AIR common stockholders, Shares									128,775	126,164	128,469
Effect of dilutive securities, Shares										271	146
Effect of dilutive securities, Per share amount										$ (0.01)
Net (loss) income attributable to AIR per common share – diluted									$ (0.85)	$ 3.90	$ 5.38

Earnings per Share and per Un_4

Earnings per Share and per Unit (Details Textual) shares in Millions	Dec. 31, 2020shares
Earnings Per Share [Abstract]
Number of shares potentially redeemable for (in shares)	2.1

Fair Value Measurements (Detail

Fair Value Measurements (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized cost of the investment in available-for-sale debt securities	$ 97.1	$ 90
Payments for purchase of swaption	$ 12.1
Derivative strike rate	1.68%
Derivative, description of terms	We receive a cash settlement in the future if the prevailing interest rate is higher than the 1.68% strike price. The amount of future cash settlement is limited if the prevailing interest rate exceeds 2.78%. Alternatively, if interest rates were to decrease below the specified strike price, we would not receive a cash settlement.
Derivative strike rate for limited settlement	2.78%
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of real estate measure on a nonrecurring basis	$ 34.4	$ 0
Available-for-sale Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Face amount of investment in available-for-sale debt securities	$ 100.9
Expected remaining term of available for sale securities	7 months 6 days

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Fair Value for AFS Debt Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
AFS debt securities	$ 100,151	$ 94,251
Fair value recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
AFS debt securities	100,151	94,251
Interest rate option	13,177	0
Fair value recurring [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
AFS debt securities	0	0
Interest rate option	0	0
Fair value recurring [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
AFS debt securities	100,151	94,251
Interest rate option	13,177	0
Fair value recurring [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
AFS debt securities	0	0
Interest rate option	$ 0	$ 0

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Carrying Value and Fair Value of Non-recourse Property Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Non-recourse property debt	$ 4,243,000	$ 4,012,805
Non-recourse property debt [Member] | Fair value Non-recurring [Member] | Carrying Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Non-recourse property debt	3,646,093	3,755,153
Non-recourse property debt [Member] | Fair value Non-recurring [Member] | Fair Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Non-recourse property debt	$ 3,730,621	$ 3,798,789

Variable Interest Entities (Det

Variable Interest Entities (Details) $ in Thousands	Dec. 31, 2020USD ($)PropertyEntityUnit	Sep. 08, 2020apartment_homeMulti_family_apartment	Dec. 31, 2019USD ($)PropertyEntityUnit
Number of apartment communities | Multi_family_apartment		12
Number of apartment homes in apartment communities | apartment_home		4,051
Net real estate	$ 5,013,359		$ 5,083,140
Cash and cash equivalents	44,214		136,458
Restricted cash	29,266		30,083
Other assets	576,026		604,593
Non-recourse property debt secured by AIR communities, net	3,628,236		3,737,805
Accrued liabilities and other	$ 598,736		$ 270,487
Variable Interest Entity, Primary Beneficiary [Member]
VIEs with interests in apartment communities | Entity	5		5
Number of apartment communities | Property	16		5
Number of apartment homes in apartment communities | Unit	5,369		2,016
Net real estate	$ 1,125,315		$ 201,425
Cash and cash equivalents	10,548		4,153
Restricted cash	8,818		2,047
Other assets	23,870		18,731
Non-recourse property debt secured by AIR communities, net	1,278,318		175,550
Accrued liabilities and other	$ 34,038		$ 23,780

Variable Interest Entities (D_2

Variable Interest Entities (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Sep. 08, 2020	Dec. 31, 2019
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Investment owned amount		$ 461,000
Option to acquire equity interest in partnership, percentage	30.00%
Other assets investment	$ 307,362		$ 280,258
Parkmerced Investment [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Investment owned amount	$ 275,000
Option to acquire equity interest in partnership, percentage	30.00%
Equity method investment, interest rate percentage	10.00%
Equity method investment, term	5 years
Equity method investment, right to extend term	5 years
Other assets investment	$ 307,400

Business Segments (Details Text

Business Segments (Details Textual)	12 Months Ended
	Dec. 31, 2020Propertyapartment_homeSegment	Sep. 08, 2020apartment_homeMulti_family_apartment
Business Segments (Textual) [Abstract]
Number of reportable segments | Segment	2
Number of owned and managed apartment communities in segments | Multi_family_apartment		12
Number of apartment homes in apartment communities		4,051
Wholly And Partially Owned Consolidated Properties | Same Store [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	91
Number of apartment homes in apartment communities	25,201
Wholly And Partially Owned Consolidated Properties | Other Real Estate [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	8
Number of apartment homes in apartment communities	1,391

Business Segments - Summary of

Business Segments - Summary of Information for Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary information for the reportable segments
Total revenues	$ 173,746	$ 178,124	$ 181,643	$ 186,043	$ 191,831	$ 192,013	$ 190,311	$ 196,447	$ 719,556	$ 770,602	$ 840,247
Other operating expenses not allocated to segments									488,461	383,635	399,377
Total operating expenses									737,497	644,876	664,101
Proportionate property net operating income (loss)									(17,941)	125,726	176,146
Other items included in income (loss) before income tax expense									(1,194)	363,111	506,120
(Loss) income from continuing operations before income tax (expense) benefit and discontinued operations									(19,135)	488,837	682,266
Real Estate
Summary information for the reportable segments
Property operating expenses									249,036	261,241	264,724
Segment Reconciling Items [Member]
Summary information for the reportable segments
Total revenues									44,370	27,235	25,936
Total operating expenses									31,555	25,190	23,842
Proportionate property net operating income (loss)									12,815	2,045	2,094
(Loss) income from continuing operations before income tax (expense) benefit and discontinued operations									12,815	2,045	2,094
Segment Reconciling Items [Member] | Real Estate
Summary information for the reportable segments
Property operating expenses									31,555	25,190	23,842
Corporate Non-Segment [Member]
Summary information for the reportable segments
Total revenues									6,139	40,381	146,026
Other operating expenses not allocated to segments									488,461	383,635	399,377
Total operating expenses									513,656	426,922	455,688
Proportionate property net operating income (loss)									(507,517)	(386,541)	(309,662)
Other items included in income (loss) before income tax expense									(1,194)	363,111	506,120
(Loss) income from continuing operations before income tax (expense) benefit and discontinued operations									(508,711)	(23,430)	196,458
Corporate Non-Segment [Member] | Real Estate
Summary information for the reportable segments
Property operating expenses									25,195	43,287	56,311
Same Store [Member] | Operating Segments [Member]
Summary information for the reportable segments
Total revenues									655,853	689,255	645,917
Total operating expenses									182,967	184,150	174,708
Proportionate property net operating income (loss)									472,886	505,105	471,209
(Loss) income from continuing operations before income tax (expense) benefit and discontinued operations									472,886	505,105	471,209
Same Store [Member] | Operating Segments [Member] | Real Estate
Summary information for the reportable segments
Property operating expenses									182,967	184,150	174,708
Other Real Estate [Member] | Operating Segments [Member]
Summary information for the reportable segments
Total revenues									13,194	13,731	22,368
Total operating expenses									9,319	8,614	9,863
Proportionate property net operating income (loss)									3,875	5,117	12,505
(Loss) income from continuing operations before income tax (expense) benefit and discontinued operations									3,875	5,117	12,505
Other Real Estate [Member] | Operating Segments [Member] | Real Estate
Summary information for the reportable segments
Property operating expenses									$ 9,319	$ 8,614	$ 9,863

Business Segments - Reconciliat

Business Segments - Reconciliation of Assets from Segment to Consolidated (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total assets	$ 6,229,278	$ 6,909,256
Total assets	0	1,022,696
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Total assets		1,022,696
Corporate Non-Segment [Member]
Segment Reporting Information [Line Items]
Total assets	1,047,506	715,230
Same Store [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total assets	4,545,476	4,692,491
Other Real Estate [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total assets	$ 636,296	$ 478,839

Business Segments - Capital Add

Business Segments - Capital Additions Related to Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Capital additions	$ 328,741	$ 363,003	$ 290,065
Same Store [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Capital additions	109,461	200,979	218,986
Other Real Estate [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Capital additions	$ 219,280	$ 162,024	$ 71,079

Unaudited Summarized Consolid_3

Unaudited Summarized Consolidated Quarterly Information - Summary of Unaudited Consolidated Quarterly Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summarized unaudited consolidated quarterly information
Total revenues	$ 173,746	$ 178,124	$ 181,643	$ 186,043	$ 191,831	$ 192,013	$ 190,311	$ 196,447	$ 719,556	$ 770,602	$ 840,247
Net income (loss) from continuing operations	(132,169)	(27,393)	40,079	4,911	138,678	85	63,818	285,951	(114,572)	488,532	695,612
Net income from discontinued operations	1,459	2,578	3,125	4,066	4,088	3,885	6,178	5,344	11,228	19,495	20,991
Net income (loss) attributable to AIR common stockholders	$ (125,174)	$ (25,046)	$ 39,212	$ 6,679	$ 133,339	$ 2,003	$ 59,234	$ 271,568	$ (104,329)	$ 466,144	$ 656,597
Net income (loss) attributable to AIR per common share – basic	$ (0.96)	$ (0.21)	$ 0.33	$ 0.06	$ 1.11	$ 0.02	$ 0.49	$ 2.33	$ (0.85)	$ 3.91	$ 5.38
Net income (loss) attributable to AIR per common share – diluted	$ (0.96)	$ (0.21)	$ 0.33	$ 0.06	$ 1.11	$ 0.02	$ 0.49	$ 2.33	$ (0.85)	$ 3.90	$ 5.37
AIMCO PROPERTIES, L.P. [Member]
Summarized unaudited consolidated quarterly information
Total revenues	$ 173,746	$ 178,124	$ 181,643	$ 186,043	$ 191,831	$ 192,013	$ 190,311	$ 196,447
Net income (loss) from continuing operations	(132,169)	(27,393)	40,079	4,911	138,678	85	63,818	285,951
Net income from discontinued operations	1,459	2,578	3,125	4,066	4,088	3,885	6,178	5,344
Net income (loss) attributable to AIR common stockholders	$ (131,746)	$ (26,387)	$ 41,319	$ 7,047	$ 140,583	$ 2,138	$ 62,817	$ 286,639
Net income (loss) attributable to AIR per common share – basic	$ (0.96)	$ (0.21)	$ 0.33	$ 0.06	$ 0.90	$ 0.02	$ 0.50	$ 2.33
Net income (loss) attributable to AIR per common share – diluted	$ (0.96)	$ (0.21)	$ 0.33	$ 0.06	$ 0.90	$ 0.02	$ 0.50	$ 2.33

Schedule III_ Real Estate and A

Schedule III: Real Estate and Accumulated Depreciation - Schedule of Real Estate and Accumulated Depreciation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)apartment_home	Sep. 08, 2020apartment_home
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of apartment homes | apartment_home		4,051
Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of apartment homes | apartment_home	26,592
Initial Cost, Land	$ 1,478,371
Initial Cost, Buildings and Improvements	2,956,079
Costs Capitalized Subsequent to Consolidation	3,171,170
Land	1,341,615
Buildings and Improvements	6,127,249
Total	7,468,864
Accumulated Depreciation (AD)	(2,455,505)
Total Cost Net of Accumulated Depreciation	5,013,359
Encumbrances	$ 3,646,093
Same Store Sales [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of apartment homes | apartment_home	25,201
Initial Cost, Land	$ 1,333,899
Initial Cost, Buildings and Improvements	2,913,666
Costs Capitalized Subsequent to Consolidation	2,581,861
Land	1,244,424
Buildings and Improvements	5,495,527
Total	6,739,951
Accumulated Depreciation (AD)	(2,344,168)
Total Cost Net of Accumulated Depreciation	4,395,783
Encumbrances	$ 3,588,079
Same Store Sales [Member] | 100 Forest Place [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Dec. 31, 1997
Location	Oak Park, IL
Year Built	1987
Number of apartment homes | apartment_home	234
Initial Cost, Land	$ 2,664
Initial Cost, Buildings and Improvements	18,815
Costs Capitalized Subsequent to Consolidation	10,235
Land	2,664
Buildings and Improvements	29,050
Total	31,714
Accumulated Depreciation (AD)	(16,704)
Total Cost Net of Accumulated Depreciation	15,010
Encumbrances	$ 33,832
Same Store Sales [Member] | 182-188 Columbus Avenue [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Feb. 28, 2007
Location	New York, NY
Year Built	1910
Number of apartment homes | apartment_home	32
Initial Cost, Land	$ 19,123
Initial Cost, Buildings and Improvements	3,300
Costs Capitalized Subsequent to Consolidation	5,629
Land	19,123
Buildings and Improvements	8,929
Total	28,052
Accumulated Depreciation (AD)	(4,993)
Total Cost Net of Accumulated Depreciation	23,059
Encumbrances	$ 13,336
Same Store Sales [Member] | 1582 First Avenue [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Mar. 31, 2005
Location	New York, NY
Year Built	1900
Number of apartment homes | apartment_home	17
Initial Cost, Land	$ 4,281
Initial Cost, Buildings and Improvements	752
Costs Capitalized Subsequent to Consolidation	548
Land	4,281
Buildings and Improvements	1,300
Total	5,581
Accumulated Depreciation (AD)	(719)
Total Cost Net of Accumulated Depreciation	4,862
Encumbrances	$ 2,177
Same Store Sales [Member] | 21 Fitzsimons [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Aug. 31, 2014
Location	Aurora, CO
Year Built	2008
Number of apartment homes | apartment_home	600
Initial Cost, Land	$ 12,864
Initial Cost, Buildings and Improvements	104,720
Costs Capitalized Subsequent to Consolidation	31,377
Land	12,864
Buildings and Improvements	136,097
Total	148,961
Accumulated Depreciation (AD)	(33,121)
Total Cost Net of Accumulated Depreciation	115,840
Encumbrances	$ 87,612
Same Store Sales [Member] | 306 East 89th Street [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Jul. 31, 2004
Location	New York, NY
Year Built	1930
Number of apartment homes | apartment_home	20
Initial Cost, Land	$ 2,680
Initial Cost, Buildings and Improvements	1,006
Costs Capitalized Subsequent to Consolidation	1,105
Land	2,680
Buildings and Improvements	2,111
Total	4,791
Accumulated Depreciation (AD)	(1,153)
Total Cost Net of Accumulated Depreciation	3,638
Encumbrances	$ 1,776
Same Store Sales [Member] | 311 & 313 East 73rd Street [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Mar. 31, 2003
Location	New York, NY
Year Built	1904
Number of apartment homes | apartment_home	34
Initial Cost, Land	$ 5,678
Initial Cost, Buildings and Improvements	1,609
Costs Capitalized Subsequent to Consolidation	604
Land	5,678
Buildings and Improvements	2,213
Total	7,891
Accumulated Depreciation (AD)	(1,721)
Total Cost Net of Accumulated Depreciation	6,170
Encumbrances	$ 0
Same Store Sales [Member] | 464-466 Amsterdam & 200-210 [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Feb. 28, 2007
Location	New York, NY
Year Built	1910
Number of apartment homes | apartment_home	71
Initial Cost, Land	$ 25,553
Initial Cost, Buildings and Improvements	7,101
Costs Capitalized Subsequent to Consolidation	11,476
Land	25,553
Buildings and Improvements	18,577
Total	44,130
Accumulated Depreciation (AD)	(6,681)
Total Cost Net of Accumulated Depreciation	37,449
Encumbrances	$ 19,653
Same Store Sales [Member] | 510 East 88th Street [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Jan. 31, 2004
Location	New York, NY
Year Built	1900
Number of apartment homes | apartment_home	20
Initial Cost, Land	$ 3,163
Initial Cost, Buildings and Improvements	1,002
Costs Capitalized Subsequent to Consolidation	642
Land	3,163
Buildings and Improvements	1,644
Total	4,807
Accumulated Depreciation (AD)	(788)
Total Cost Net of Accumulated Depreciation	4,019
Encumbrances	$ 0
Same Store Sales [Member] | 234 East 88th Street [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Jan. 31, 2014
Location	New York, NY
Year Built	1900
Number of apartment homes | apartment_home	20
Initial Cost, Land	$ 2,448
Initial Cost, Buildings and Improvements	4,449
Costs Capitalized Subsequent to Consolidation	841
Land	2,448
Buildings and Improvements	5,290
Total	7,738
Accumulated Depreciation (AD)	(1,661)
Total Cost Net of Accumulated Depreciation	6,077
Encumbrances	$ 0
Same Store Sales [Member] | 322-324 East 61st Street [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Mar. 31, 2005
Location	New York, NY
Year Built	1900
Number of apartment homes | apartment_home	40
Initial Cost, Land	$ 6,372
Initial Cost, Buildings and Improvements	2,224
Costs Capitalized Subsequent to Consolidation	1,477
Land	6,372
Buildings and Improvements	3,701
Total	10,073
Accumulated Depreciation (AD)	(2,054)
Total Cost Net of Accumulated Depreciation	8,019
Encumbrances	$ 3,266
Same Store Sales [Member] | 777 South Broad Street [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	May 31, 2018
Location	Philadelphia, PA
Year Built	2010
Number of apartment homes | apartment_home	146
Initial Cost, Land	$ 6,986
Initial Cost, Buildings and Improvements	67,512
Costs Capitalized Subsequent to Consolidation	3,317
Land	6,986
Buildings and Improvements	70,829
Total	77,815
Accumulated Depreciation (AD)	(6,896)
Total Cost Net of Accumulated Depreciation	70,919
Encumbrances	$ 55,496
Same Store Sales [Member] | 3400 Avenue of the Arts [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Mar. 31, 2002
Location	Costa Mesa, CA
Year Built	1987
Number of apartment homes | apartment_home	770
Initial Cost, Land	$ 57,241
Initial Cost, Buildings and Improvements	65,506
Costs Capitalized Subsequent to Consolidation	90,493
Land	57,241
Buildings and Improvements	155,999
Total	213,240
Accumulated Depreciation (AD)	(96,067)
Total Cost Net of Accumulated Depreciation	117,173
Encumbrances	$ 139,094
Same Store Sales [Member] | Avery Row [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Dec. 31, 2018
Location	Arlington, VA
Year Built	2013
Number of apartment homes | apartment_home	67
Initial Cost, Land	$ 8,165
Initial Cost, Buildings and Improvements	21,348
Costs Capitalized Subsequent to Consolidation	2,097
Land	8,165
Buildings and Improvements	23,445
Total	31,610
Accumulated Depreciation (AD)	(1,980)
Total Cost Net of Accumulated Depreciation	29,630
Encumbrances	$ 0
Same Store Sales [Member] | 452 East 78th Street [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Jan. 31, 2004
Location	New York, NY
Year Built	1900
Number of apartment homes | apartment_home	12
Initial Cost, Land	$ 1,982
Initial Cost, Buildings and Improvements	608
Costs Capitalized Subsequent to Consolidation	538
Land	1,982
Buildings and Improvements	1,146
Total	3,128
Accumulated Depreciation (AD)	(534)
Total Cost Net of Accumulated Depreciation	2,594
Encumbrances	$ 0
Same Store Sales [Member] | Bay Parc Plaza [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Sep. 30, 2004
Location	Miami, FL
Year Built	2000
Number of apartment homes | apartment_home	474
Initial Cost, Land	$ 22,680
Initial Cost, Buildings and Improvements	41,847
Costs Capitalized Subsequent to Consolidation	41,403
Land	22,680
Buildings and Improvements	83,250
Total	105,930
Accumulated Depreciation (AD)	(29,744)
Total Cost Net of Accumulated Depreciation	76,186
Encumbrances	$ 75,046
Same Store Sales [Member] | 514-516 East 88th Street [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Mar. 31, 2005
Location	New York, NY
Year Built	1900
Number of apartment homes | apartment_home	36
Initial Cost, Land	$ 6,282
Initial Cost, Buildings and Improvements	2,168
Costs Capitalized Subsequent to Consolidation	1,565
Land	6,282
Buildings and Improvements	3,733
Total	10,015
Accumulated Depreciation (AD)	(2,033)
Total Cost Net of Accumulated Depreciation	7,982
Encumbrances	$ 3,540
Same Store Sales [Member] | 518 East 88th Street [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Jan. 31, 2014
Location	New York, NY
Year Built	1900
Number of apartment homes | apartment_home	20
Initial Cost, Land	$ 2,233
Initial Cost, Buildings and Improvements	4,315
Costs Capitalized Subsequent to Consolidation	630
Land	2,233
Buildings and Improvements	4,945
Total	7,178
Accumulated Depreciation (AD)	(1,592)
Total Cost Net of Accumulated Depreciation	5,586
Encumbrances	$ 0
Same Store Sales [Member] | Bent Tree Apartments [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Feb. 28, 2018
Location	Centreville, VA
Year Built	1986
Number of apartment homes | apartment_home	748
Initial Cost, Land	$ 46,975
Initial Cost, Buildings and Improvements	113,695
Costs Capitalized Subsequent to Consolidation	30,349
Land	46,975
Buildings and Improvements	144,044
Total	191,019
Accumulated Depreciation (AD)	(16,284)
Total Cost Net of Accumulated Depreciation	174,735
Encumbrances	$ 59,777
Same Store Sales [Member] | Axiom [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Apr. 30, 2015
Location	Cambridge, MA
Year Built	2015
Number of apartment homes | apartment_home	115
Initial Cost, Land	$ 0
Initial Cost, Buildings and Improvements	63,612
Costs Capitalized Subsequent to Consolidation	2,883
Land	0
Buildings and Improvements	66,495
Total	66,495
Accumulated Depreciation (AD)	(14,037)
Total Cost Net of Accumulated Depreciation	52,458
Encumbrances	$ 31,501
Same Store Sales [Member] | Bay Ridge at Nashua [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jan. 31, 2003
Location	Nashua, NH
Year Built	1984
Number of apartment homes | apartment_home	412
Initial Cost, Land	$ 3,262
Initial Cost, Buildings and Improvements	40,713
Costs Capitalized Subsequent to Consolidation	16,929
Land	3,262
Buildings and Improvements	57,642
Total	60,904
Accumulated Depreciation (AD)	(29,360)
Total Cost Net of Accumulated Depreciation	31,544
Encumbrances	$ 49,717
Same Store Sales [Member] | Bayberry Hill Estates [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Aug. 31, 2002
Location	Framingham, MA
Year Built	1971
Number of apartment homes | apartment_home	424
Initial Cost, Land	$ 19,944
Initial Cost, Buildings and Improvements	35,945
Costs Capitalized Subsequent to Consolidation	25,376
Land	19,944
Buildings and Improvements	61,321
Total	81,265
Accumulated Depreciation (AD)	(33,451)
Total Cost Net of Accumulated Depreciation	47,814
Encumbrances	$ 43,393
Same Store Sales [Member] | Columbus Avenue [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Sep. 30, 2003
Location	New York, NY
Year Built	1880
Number of apartment homes | apartment_home	59
Initial Cost, Land	$ 35,527
Initial Cost, Buildings and Improvements	9,450
Costs Capitalized Subsequent to Consolidation	9,155
Land	35,527
Buildings and Improvements	18,605
Total	54,132
Accumulated Depreciation (AD)	(13,318)
Total Cost Net of Accumulated Depreciation	40,814
Encumbrances	$ 23,986
Same Store Sales [Member] | Boston Lofts [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Apr. 30, 2001
Location	Denver, CO
Year Built	1890
Number of apartment homes | apartment_home	158
Initial Cost, Land	$ 3,446
Initial Cost, Buildings and Improvements	20,589
Costs Capitalized Subsequent to Consolidation	6,501
Land	3,446
Buildings and Improvements	27,090
Total	30,536
Accumulated Depreciation (AD)	(15,054)
Total Cost Net of Accumulated Depreciation	15,482
Encumbrances	$ 0
Same Store Sales [Member] | Boulder Creek [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jul. 31, 1994
Location	Boulder, CO
Year Built	1973
Number of apartment homes | apartment_home	221
Initial Cost, Land	$ 754
Initial Cost, Buildings and Improvements	7,730
Costs Capitalized Subsequent to Consolidation	19,320
Land	754
Buildings and Improvements	27,050
Total	27,804
Accumulated Depreciation (AD)	(20,010)
Total Cost Net of Accumulated Depreciation	7,794
Encumbrances	$ 37,194
Same Store Sales [Member] | Flamingo Point, Center Tower [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Sep. 30, 1997
Location	Miami Beach, FL
Year Built	2003
Number of apartment homes | apartment_home	513
Initial Cost, Land	$ 15,179
Initial Cost, Buildings and Improvements	29,358
Costs Capitalized Subsequent to Consolidation	203,209
Land	15,179
Buildings and Improvements	232,567
Total	247,746
Accumulated Depreciation (AD)	(107,729)
Total Cost Net of Accumulated Depreciation	140,017
Encumbrances	$ 0
Same Store Sales [Member] | Broadcast Center [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2002
Location	Los Angeles, CA
Year Built	1990
Number of apartment homes | apartment_home	279
Initial Cost, Land	$ 29,407
Initial Cost, Buildings and Improvements	41,244
Costs Capitalized Subsequent to Consolidation	32,598
Land	29,407
Buildings and Improvements	73,842
Total	103,249
Accumulated Depreciation (AD)	(34,493)
Total Cost Net of Accumulated Depreciation	68,756
Encumbrances	$ 94,978
Same Store Sales [Member] | Flamingo Point, South Tower [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Sep. 30, 1997
Location	Miami Beach, FL
Year Built	1960
Number of apartment homes | apartment_home	222
Initial Cost, Land	$ 0
Initial Cost, Buildings and Improvements	0
Costs Capitalized Subsequent to Consolidation	74,578
Land	0
Buildings and Improvements	74,578
Total	74,578
Accumulated Depreciation (AD)	(12,504)
Total Cost Net of Accumulated Depreciation	62,074
Encumbrances	$ 0
Same Store Sales [Member] | Broadway Lofts [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Sep. 30, 2012
Location	San Diego, CA
Year Built	1909
Number of apartment homes | apartment_home	84
Initial Cost, Land	$ 5,367
Initial Cost, Buildings and Improvements	14,442
Costs Capitalized Subsequent to Consolidation	8,187
Land	5,367
Buildings and Improvements	22,629
Total	27,996
Accumulated Depreciation (AD)	(7,543)
Total Cost Net of Accumulated Depreciation	20,453
Encumbrances	$ 11,056
Same Store Sales [Member] | Burke Shire Commons [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2001
Location	Burke, VA
Year Built	1986
Number of apartment homes | apartment_home	360
Initial Cost, Land	$ 4,867
Initial Cost, Buildings and Improvements	23,617
Costs Capitalized Subsequent to Consolidation	18,810
Land	4,867
Buildings and Improvements	42,427
Total	47,294
Accumulated Depreciation (AD)	(28,554)
Total Cost Net of Accumulated Depreciation	18,740
Encumbrances	$ 55,809
Same Store Sales [Member] | Calhoun Beach Club [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Dec. 31, 1998
Location	Minneapolis, MN
Year Built	1928
Number of apartment homes | apartment_home	332
Initial Cost, Land	$ 11,708
Initial Cost, Buildings and Improvements	73,334
Costs Capitalized Subsequent to Consolidation	63,689
Land	11,708
Buildings and Improvements	137,023
Total	148,731
Accumulated Depreciation (AD)	(87,464)
Total Cost Net of Accumulated Depreciation	61,267
Encumbrances	$ 0
Same Store Sales [Member] | Heritage Park Escondido [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Oct. 31, 2000
Location	Escondido, CA
Year Built	1986
Number of apartment homes | apartment_home	196
Initial Cost, Land	$ 1,055
Initial Cost, Buildings and Improvements	7,565
Costs Capitalized Subsequent to Consolidation	3,988
Land	1,055
Buildings and Improvements	11,553
Total	12,608
Accumulated Depreciation (AD)	(7,576)
Total Cost Net of Accumulated Depreciation	5,032
Encumbrances	$ 5,590
Same Store Sales [Member] | Canyon Terrace [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2002
Location	Saugus, CA
Year Built	1984
Number of apartment homes | apartment_home	130
Initial Cost, Land	$ 7,508
Initial Cost, Buildings and Improvements	6,601
Costs Capitalized Subsequent to Consolidation	6,592
Land	7,508
Buildings and Improvements	13,193
Total	20,701
Accumulated Depreciation (AD)	(7,961)
Total Cost Net of Accumulated Depreciation	12,740
Encumbrances	$ 0
Same Store Sales [Member] | Heritage Park Livermore [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Oct. 31, 2000
Location	Livermore, CA
Year Built	1988
Number of apartment homes | apartment_home	167
Initial Cost, Land	$ 0
Initial Cost, Buildings and Improvements	10,209
Costs Capitalized Subsequent to Consolidation	2,157
Land	0
Buildings and Improvements	12,366
Total	12,366
Accumulated Depreciation (AD)	(8,893)
Total Cost Net of Accumulated Depreciation	3,473
Encumbrances	$ 5,810
Same Store Sales [Member] | Heritage Village Anaheim [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Oct. 31, 2000
Location	Anaheim, CA
Year Built	1986
Number of apartment homes | apartment_home	196
Initial Cost, Land	$ 1,832
Initial Cost, Buildings and Improvements	8,541
Costs Capitalized Subsequent to Consolidation	3,393
Land	1,832
Buildings and Improvements	11,934
Total	13,766
Accumulated Depreciation (AD)	(7,768)
Total Cost Net of Accumulated Depreciation	5,998
Encumbrances	$ 6,788
Same Store Sales [Member] | Charlesbank Apartment Homes [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Sep. 30, 2013
Location	Watertown, MA
Year Built	2012
Number of apartment homes | apartment_home	44
Initial Cost, Land	$ 3,399
Initial Cost, Buildings and Improvements	11,726
Costs Capitalized Subsequent to Consolidation	1,115
Land	3,399
Buildings and Improvements	12,841
Total	16,240
Accumulated Depreciation (AD)	(3,463)
Total Cost Net of Accumulated Depreciation	12,777
Encumbrances	$ 0
Same Store Sales [Member] | Chestnut Hall [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Oct. 31, 2006
Location	Philadelphia, PA
Year Built	1923
Number of apartment homes | apartment_home	315
Initial Cost, Land	$ 12,338
Initial Cost, Buildings and Improvements	14,299
Costs Capitalized Subsequent to Consolidation	14,513
Land	12,338
Buildings and Improvements	28,812
Total	41,150
Accumulated Depreciation (AD)	(13,748)
Total Cost Net of Accumulated Depreciation	27,402
Encumbrances	$ 34,985
Same Store Sales [Member] | Creekside [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jan. 31, 2000
Location	Denver, CO
Year Built	1974
Number of apartment homes | apartment_home	328
Initial Cost, Land	$ 3,189
Initial Cost, Buildings and Improvements	12,698
Costs Capitalized Subsequent to Consolidation	7,328
Land	3,189
Buildings and Improvements	20,026
Total	23,215
Accumulated Depreciation (AD)	(14,096)
Total Cost Net of Accumulated Depreciation	9,119
Encumbrances	$ 10,792
Same Store Sales [Member] | Crescent at West Hollywood, The [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Mar. 31, 2002
Location	West Hollywood, CA
Year Built	1985
Number of apartment homes | apartment_home	130
Initial Cost, Land	$ 15,765
Initial Cost, Buildings and Improvements	10,215
Costs Capitalized Subsequent to Consolidation	8,683
Land	15,765
Buildings and Improvements	18,898
Total	34,663
Accumulated Depreciation (AD)	(13,024)
Total Cost Net of Accumulated Depreciation	21,639
Encumbrances	$ 38,643
Same Store Sales [Member] | Four Quarters Habitat [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jan. 31, 2006
Location	Miami, FL
Year Built	1976
Number of apartment homes | apartment_home	336
Initial Cost, Land	$ 2,379
Initial Cost, Buildings and Improvements	17,199
Costs Capitalized Subsequent to Consolidation	34,208
Land	2,379
Buildings and Improvements	51,407
Total	53,786
Accumulated Depreciation (AD)	(34,722)
Total Cost Net of Accumulated Depreciation	19,064
Encumbrances	$ 49,792
Same Store Sales [Member] | Foxchase [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Dec. 31, 1997
Location	Alexandria, VA
Year Built	1940
Number of apartment homes | apartment_home	2,113
Initial Cost, Land	$ 15,496
Initial Cost, Buildings and Improvements	96,062
Costs Capitalized Subsequent to Consolidation	63,632
Land	15,496
Buildings and Improvements	159,694
Total	175,190
Accumulated Depreciation (AD)	(94,709)
Total Cost Net of Accumulated Depreciation	80,481
Encumbrances	$ 0
Same Store Sales [Member] | Locust On The Park [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	May 31, 2018
Location	Philadelphia, PA
Year Built	1911
Number of apartment homes | apartment_home	152
Initial Cost, Land	$ 5,292
Initial Cost, Buildings and Improvements	53,823
Costs Capitalized Subsequent to Consolidation	5,801
Land	5,292
Buildings and Improvements	59,624
Total	64,916
Accumulated Depreciation (AD)	(5,982)
Total Cost Net of Accumulated Depreciation	58,934
Encumbrances	$ 35,000
Same Store Sales [Member] | Georgetown [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Aug. 31, 2002
Location	Framingham, MA
Year Built	1964
Number of apartment homes | apartment_home	207
Initial Cost, Land	$ 12,351
Initial Cost, Buildings and Improvements	13,168
Costs Capitalized Subsequent to Consolidation	5,068
Land	12,351
Buildings and Improvements	18,236
Total	30,587
Accumulated Depreciation (AD)	(9,270)
Total Cost Net of Accumulated Depreciation	21,317
Encumbrances	$ 0
Same Store Sales [Member] | Georgetown II [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Aug. 31, 2002
Location	Framingham, MA
Year Built	1958
Number of apartment homes | apartment_home	72
Initial Cost, Land	$ 4,577
Initial Cost, Buildings and Improvements	4,057
Costs Capitalized Subsequent to Consolidation	2,145
Land	4,577
Buildings and Improvements	6,202
Total	10,779
Accumulated Depreciation (AD)	(4,032)
Total Cost Net of Accumulated Depreciation	6,747
Encumbrances	$ 0
Same Store Sales [Member] | Hidden Cove [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jul. 31, 1998
Location	Escondido, CA
Year Built	1983
Number of apartment homes | apartment_home	334
Initial Cost, Land	$ 3,043
Initial Cost, Buildings and Improvements	17,616
Costs Capitalized Subsequent to Consolidation	10,456
Land	3,043
Buildings and Improvements	28,072
Total	31,115
Accumulated Depreciation (AD)	(17,083)
Total Cost Net of Accumulated Depreciation	14,032
Encumbrances	$ 64,757
Same Store Sales [Member] | Hidden Cove II [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jul. 31, 2007
Location	Escondido, CA
Year Built	1986
Number of apartment homes | apartment_home	118
Initial Cost, Land	$ 12,849
Initial Cost, Buildings and Improvements	6,530
Costs Capitalized Subsequent to Consolidation	5,071
Land	12,849
Buildings and Improvements	11,601
Total	24,450
Accumulated Depreciation (AD)	(6,061)
Total Cost Net of Accumulated Depreciation	18,389
Encumbrances	$ 25,183
Same Store Sales [Member] | Hillcreste [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2002
Location	Century City, CA
Year Built	1989
Number of apartment homes | apartment_home	315
Initial Cost, Land	$ 35,862
Initial Cost, Buildings and Improvements	47,216
Costs Capitalized Subsequent to Consolidation	15,897
Land	35,862
Buildings and Improvements	63,113
Total	98,975
Accumulated Depreciation (AD)	(31,011)
Total Cost Net of Accumulated Depreciation	67,964
Encumbrances	$ 60,310
Same Store Sales [Member] | Horizons West Apartments [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Dec. 31, 2006
Location	Pacifica, CA
Year Built	1970
Number of apartment homes | apartment_home	78
Initial Cost, Land	$ 8,887
Initial Cost, Buildings and Improvements	6,377
Costs Capitalized Subsequent to Consolidation	3,562
Land	8,887
Buildings and Improvements	9,939
Total	18,826
Accumulated Depreciation (AD)	(4,666)
Total Cost Net of Accumulated Depreciation	14,160
Encumbrances	$ 0
Same Store Sales [Member] | Hunt Club [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Sep. 30, 2000
Location	Gaithersburg, MD
Year Built	1986
Number of apartment homes | apartment_home	336
Initial Cost, Land	$ 17,859
Initial Cost, Buildings and Improvements	13,149
Costs Capitalized Subsequent to Consolidation	12,592
Land	17,859
Buildings and Improvements	25,741
Total	43,600
Accumulated Depreciation (AD)	(16,198)
Total Cost Net of Accumulated Depreciation	27,402
Encumbrances	$ 0
Same Store Sales [Member] | Indian Oaks [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2002
Location	Simi Valley, CA
Year Built	1986
Number of apartment homes | apartment_home	254
Initial Cost, Land	$ 24,523
Initial Cost, Buildings and Improvements	15,801
Costs Capitalized Subsequent to Consolidation	11,439
Land	24,523
Buildings and Improvements	27,240
Total	51,763
Accumulated Depreciation (AD)	(15,790)
Total Cost Net of Accumulated Depreciation	35,973
Encumbrances	$ 58,955
Same Store Sales [Member] | Indigo [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Aug. 31, 2016
Location	Redwood City, CA
Year Built	2016
Number of apartment homes | apartment_home	463
Initial Cost, Land	$ 26,932
Initial Cost, Buildings and Improvements	296,116
Costs Capitalized Subsequent to Consolidation	5,569
Land	26,932
Buildings and Improvements	301,685
Total	328,617
Accumulated Depreciation (AD)	(46,343)
Total Cost Net of Accumulated Depreciation	282,274
Encumbrances	$ 182,161
Same Store Sales [Member] | Island Club [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Oct. 31, 2000
Location	Oceanside, CA
Year Built	1986
Number of apartment homes | apartment_home	592
Initial Cost, Land	$ 18,027
Initial Cost, Buildings and Improvements	28,654
Costs Capitalized Subsequent to Consolidation	20,499
Land	18,027
Buildings and Improvements	49,153
Total	67,180
Accumulated Depreciation (AD)	(32,779)
Total Cost Net of Accumulated Depreciation	34,401
Encumbrances	$ 91,631
Same Store Sales [Member] | Latrobe [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Jan. 31, 2003
Location	Washington, D.C.
Year Built	1980
Number of apartment homes | apartment_home	175
Initial Cost, Land	$ 3,459
Initial Cost, Buildings and Improvements	9,103
Costs Capitalized Subsequent to Consolidation	13,196
Land	3,459
Buildings and Improvements	22,299
Total	25,758
Accumulated Depreciation (AD)	(14,426)
Total Cost Net of Accumulated Depreciation	11,332
Encumbrances	$ 25,462
Same Store Sales [Member] | Laurel Crossing [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jan. 31, 2006
Location	San Mateo, CA
Year Built	1971
Number of apartment homes | apartment_home	418
Initial Cost, Land	$ 49,474
Initial Cost, Buildings and Improvements	17,756
Costs Capitalized Subsequent to Consolidation	15,114
Land	49,474
Buildings and Improvements	32,870
Total	82,344
Accumulated Depreciation (AD)	(17,785)
Total Cost Net of Accumulated Depreciation	64,559
Encumbrances	$ 102,565
Same Store Sales [Member] | Lincoln Place [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Oct. 31, 2004
Location	Venice, CA
Year Built	1951
Number of apartment homes | apartment_home	795
Initial Cost, Land	$ 128,332
Initial Cost, Buildings and Improvements	10,439
Costs Capitalized Subsequent to Consolidation	341,037
Land	44,197
Buildings and Improvements	351,476
Total	395,673
Accumulated Depreciation (AD)	(156,957)
Total Cost Net of Accumulated Depreciation	238,716
Encumbrances	$ 180,859
Same Store Sales [Member] | Malibu Canyon [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2002
Location	Calabasas, CA
Year Built	1986
Number of apartment homes | apartment_home	698
Initial Cost, Land	$ 69,834
Initial Cost, Buildings and Improvements	53,438
Costs Capitalized Subsequent to Consolidation	39,822
Land	69,834
Buildings and Improvements	93,260
Total	163,094
Accumulated Depreciation (AD)	(54,343)
Total Cost Net of Accumulated Depreciation	108,751
Encumbrances	$ 158,950
Same Store Sales [Member] | Mariners Cove [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2002
Location	San Diego, CA
Year Built	1984
Number of apartment homes | apartment_home	500
Initial Cost, Land	$ 0
Initial Cost, Buildings and Improvements	66,861
Costs Capitalized Subsequent to Consolidation	16,354
Land	0
Buildings and Improvements	83,215
Total	83,215
Accumulated Depreciation (AD)	(44,288)
Total Cost Net of Accumulated Depreciation	38,927
Encumbrances	$ 0
Same Store Sales [Member] | Merrill House [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Jan. 31, 2000
Location	Falls Church, VA
Year Built	1964
Number of apartment homes | apartment_home	159
Initial Cost, Land	$ 1,836
Initial Cost, Buildings and Improvements	10,831
Costs Capitalized Subsequent to Consolidation	8,319
Land	1,836
Buildings and Improvements	19,150
Total	20,986
Accumulated Depreciation (AD)	(11,359)
Total Cost Net of Accumulated Depreciation	9,627
Encumbrances	$ 0
Same Store Sales [Member] | One Canal [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Sep. 30, 2013
Location	Boston, MA
Year Built	2016
Number of apartment homes | apartment_home	310
Initial Cost, Land	$ 0
Initial Cost, Buildings and Improvements	15,873
Costs Capitalized Subsequent to Consolidation	182,092
Land	0
Buildings and Improvements	197,965
Total	197,965
Accumulated Depreciation (AD)	(37,688)
Total Cost Net of Accumulated Depreciation	160,277
Encumbrances	$ 106,576
Same Store Sales [Member] | Meadow Creek [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jul. 31, 1994
Location	Boulder, CO
Year Built	1968
Number of apartment homes | apartment_home	332
Initial Cost, Land	$ 1,435
Initial Cost, Buildings and Improvements	24,533
Costs Capitalized Subsequent to Consolidation	9,575
Land	1,435
Buildings and Improvements	34,108
Total	35,543
Accumulated Depreciation (AD)	(22,157)
Total Cost Net of Accumulated Depreciation	13,386
Encumbrances	$ 0
Same Store Sales [Member] | Mezzo [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Mar. 31, 2015
Location	Atlanta, GA
Year Built	2008
Number of apartment homes | apartment_home	94
Initial Cost, Land	$ 4,292
Initial Cost, Buildings and Improvements	34,178
Costs Capitalized Subsequent to Consolidation	2,171
Land	4,292
Buildings and Improvements	36,349
Total	40,641
Accumulated Depreciation (AD)	(8,419)
Total Cost Net of Accumulated Depreciation	32,222
Encumbrances	$ 0
Same Store Sales [Member] | Pacific Bay Vistas [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2001
Location	San Bruno, CA
Year Built	1987
Number of apartment homes | apartment_home	308
Initial Cost, Land	$ 28,694
Initial Cost, Buildings and Improvements	62,460
Costs Capitalized Subsequent to Consolidation	40,897
Land	23,354
Buildings and Improvements	103,357
Total	126,711
Accumulated Depreciation (AD)	(42,650)
Total Cost Net of Accumulated Depreciation	84,061
Encumbrances	$ 102,554
Same Store Sales [Member] | Monterey Grove [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jun. 30, 2008
Location	San Jose, CA
Year Built	1999
Number of apartment homes | apartment_home	224
Initial Cost, Land	$ 34,325
Initial Cost, Buildings and Improvements	21,939
Costs Capitalized Subsequent to Consolidation	16,440
Land	34,325
Buildings and Improvements	38,379
Total	72,704
Accumulated Depreciation (AD)	(14,771)
Total Cost Net of Accumulated Depreciation	57,933
Encumbrances	$ 48,698
Same Store Sales [Member] | Pacifica Park [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jul. 31, 2006
Location	Pacifica, CA
Year Built	1977
Number of apartment homes | apartment_home	104
Initial Cost, Land	$ 12,970
Initial Cost, Buildings and Improvements	6,579
Costs Capitalized Subsequent to Consolidation	8,688
Land	12,970
Buildings and Improvements	15,267
Total	28,237
Accumulated Depreciation (AD)	(8,272)
Total Cost Net of Accumulated Depreciation	19,965
Encumbrances	$ 37,264
Same Store Sales [Member] | Ocean House on Prospect [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Apr. 30, 2013
Location	La Jolla, CA
Year Built	1970
Number of apartment homes | apartment_home	53
Initial Cost, Land	$ 12,528
Initial Cost, Buildings and Improvements	18,805
Costs Capitalized Subsequent to Consolidation	16,070
Land	12,528
Buildings and Improvements	34,875
Total	47,403
Accumulated Depreciation (AD)	(10,586)
Total Cost Net of Accumulated Depreciation	36,817
Encumbrances	$ 0
Same Store Sales [Member] | Palazzo at Park La Brea, The [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Feb. 29, 2004
Location	Los Angeles, CA
Year Built	2002
Number of apartment homes | apartment_home	521
Initial Cost, Land	$ 48,362
Initial Cost, Buildings and Improvements	125,464
Costs Capitalized Subsequent to Consolidation	51,848
Land	48,362
Buildings and Improvements	177,312
Total	225,674
Accumulated Depreciation (AD)	(95,304)
Total Cost Net of Accumulated Depreciation	130,370
Encumbrances	$ 216,916
Same Store Sales [Member] | Palazzo East at Park La Brea, The [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Mar. 31, 2005
Location	Los Angeles, CA
Year Built	2005
Number of apartment homes | apartment_home	611
Initial Cost, Land	$ 72,578
Initial Cost, Buildings and Improvements	136,503
Costs Capitalized Subsequent to Consolidation	31,959
Land	72,578
Buildings and Improvements	168,462
Total	241,040
Accumulated Depreciation (AD)	(87,863)
Total Cost Net of Accumulated Depreciation	153,177
Encumbrances	$ 187,917
Same Store Sales [Member] | Peachtree Park [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jan. 31, 1996
Location	Atlanta, GA
Year Built	1969
Number of apartment homes | apartment_home	303
Initial Cost, Land	$ 4,684
Initial Cost, Buildings and Improvements	11,713
Costs Capitalized Subsequent to Consolidation	14,067
Land	4,684
Buildings and Improvements	25,780
Total	30,464
Accumulated Depreciation (AD)	(17,572)
Total Cost Net of Accumulated Depreciation	12,892
Encumbrances	$ 26,813
Same Store Sales [Member] | Preserve at Marin [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Aug. 31, 2011
Location	Corte Madera, CA
Year Built	1964
Number of apartment homes | apartment_home	126
Initial Cost, Land	$ 13,516
Initial Cost, Buildings and Improvements	30,132
Costs Capitalized Subsequent to Consolidation	83,001
Land	13,516
Buildings and Improvements	113,133
Total	126,649
Accumulated Depreciation (AD)	(37,040)
Total Cost Net of Accumulated Depreciation	89,609
Encumbrances	$ 34,603
Same Store Sales [Member] | Riverloft [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Oct. 31, 1999
Location	Philadelphia, PA
Year Built	1910
Number of apartment homes | apartment_home	184
Initial Cost, Land	$ 2,120
Initial Cost, Buildings and Improvements	11,286
Costs Capitalized Subsequent to Consolidation	38,205
Land	2,120
Buildings and Improvements	49,491
Total	51,611
Accumulated Depreciation (AD)	(28,035)
Total Cost Net of Accumulated Depreciation	23,576
Encumbrances	$ 0
Same Store Sales [Member] | Rosewood [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2002
Location	Camarillo, CA
Year Built	1976
Number of apartment homes | apartment_home	152
Initial Cost, Land	$ 12,430
Initial Cost, Buildings and Improvements	8,060
Costs Capitalized Subsequent to Consolidation	6,265
Land	12,430
Buildings and Improvements	14,325
Total	26,755
Accumulated Depreciation (AD)	(8,102)
Total Cost Net of Accumulated Depreciation	18,653
Encumbrances	$ 30,452
Same Store Sales [Member] | Royal Crest Estates [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Aug. 31, 2002
Location	North Andover, MA
Year Built	1970
Number of apartment homes | apartment_home	588
Initial Cost, Land	$ 51,292
Initial Cost, Buildings and Improvements	36,808
Costs Capitalized Subsequent to Consolidation	27,537
Land	51,292
Buildings and Improvements	64,345
Total	115,637
Accumulated Depreciation (AD)	(38,311)
Total Cost Net of Accumulated Depreciation	77,326
Encumbrances	$ 79,730
Same Store Sales [Member] | Saybrook Point [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Dec. 31, 2014
Location	San Jose, CA
Year Built	1995
Number of apartment homes | apartment_home	324
Initial Cost, Land	$ 32,842
Initial Cost, Buildings and Improvements	84,457
Costs Capitalized Subsequent to Consolidation	26,088
Land	32,842
Buildings and Improvements	110,545
Total	143,387
Accumulated Depreciation (AD)	(23,844)
Total Cost Net of Accumulated Depreciation	119,543
Encumbrances	$ 107,347
Same Store Sales [Member] | Shenandoah Crossing [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Sep. 30, 2000
Location	Fairfax, VA
Year Built	1984
Number of apartment homes | apartment_home	640
Initial Cost, Land	$ 18,200
Initial Cost, Buildings and Improvements	57,198
Costs Capitalized Subsequent to Consolidation	23,189
Land	18,200
Buildings and Improvements	80,387
Total	98,587
Accumulated Depreciation (AD)	(63,435)
Total Cost Net of Accumulated Depreciation	35,152
Encumbrances	$ 0
Same Store Sales [Member] | Springwoods at Lake Ridge [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jul. 31, 2002
Location	Woodbridge, VA
Year Built	1984
Number of apartment homes | apartment_home	180
Initial Cost, Land	$ 5,587
Initial Cost, Buildings and Improvements	7,284
Costs Capitalized Subsequent to Consolidation	2,782
Land	5,587
Buildings and Improvements	10,066
Total	15,653
Accumulated Depreciation (AD)	(4,462)
Total Cost Net of Accumulated Depreciation	11,191
Encumbrances	$ 0
Same Store Sales [Member] | Sterling Apartment Homes, The [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Oct. 31, 1999
Location	Philadelphia, PA
Year Built	1961
Number of apartment homes | apartment_home	534
Initial Cost, Land	$ 8,871
Initial Cost, Buildings and Improvements	55,365
Costs Capitalized Subsequent to Consolidation	117,915
Land	8,871
Buildings and Improvements	173,280
Total	182,151
Accumulated Depreciation (AD)	(100,897)
Total Cost Net of Accumulated Depreciation	81,254
Encumbrances	$ 138,021
Same Store Sales [Member] | Stone Creek Club [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Sep. 30, 2000
Location	Germantown, MD
Year Built	1984
Number of apartment homes | apartment_home	240
Initial Cost, Land	$ 13,593
Initial Cost, Buildings and Improvements	9,347
Costs Capitalized Subsequent to Consolidation	6,520
Land	13,593
Buildings and Improvements	15,867
Total	29,460
Accumulated Depreciation (AD)	(11,595)
Total Cost Net of Accumulated Depreciation	17,865
Encumbrances	$ 0
Same Store Sales [Member] | Township At Highlands [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Town Home
Date Consolidated	Nov. 30, 1996
Location	Centennial, CO
Year Built	1985
Number of apartment homes | apartment_home	161
Initial Cost, Land	$ 1,536
Initial Cost, Buildings and Improvements	9,773
Costs Capitalized Subsequent to Consolidation	13,101
Land	1,536
Buildings and Improvements	22,874
Total	24,410
Accumulated Depreciation (AD)	(13,967)
Total Cost Net of Accumulated Depreciation	10,443
Encumbrances	$ 0
Same Store Sales [Member] | Vantage Pointe [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Aug. 31, 2002
Location	Swampscott, MA
Year Built	1987
Number of apartment homes | apartment_home	96
Initial Cost, Land	$ 4,748
Initial Cost, Buildings and Improvements	10,089
Costs Capitalized Subsequent to Consolidation	2,559
Land	4,748
Buildings and Improvements	12,648
Total	17,396
Accumulated Depreciation (AD)	(6,020)
Total Cost Net of Accumulated Depreciation	11,376
Encumbrances	$ 0
Same Store Sales [Member] | Tremont [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Dec. 31, 2014
Location	Atlanta, GA
Year Built	2009
Number of apartment homes | apartment_home	78
Initial Cost, Land	$ 5,274
Initial Cost, Buildings and Improvements	18,011
Costs Capitalized Subsequent to Consolidation	3,270
Land	5,274
Buildings and Improvements	21,281
Total	26,555
Accumulated Depreciation (AD)	(4,974)
Total Cost Net of Accumulated Depreciation	21,581
Encumbrances	$ 0
Same Store Sales [Member] | Villa Del Sol [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2002
Location	Norwalk, CA
Year Built	1972
Number of apartment homes | apartment_home	120
Initial Cost, Land	$ 7,476
Initial Cost, Buildings and Improvements	4,861
Costs Capitalized Subsequent to Consolidation	5,423
Land	7,476
Buildings and Improvements	10,284
Total	17,760
Accumulated Depreciation (AD)	(6,332)
Total Cost Net of Accumulated Depreciation	11,428
Encumbrances	$ 0
Same Store Sales [Member] | Villas of Pasadena [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Jan. 31, 2006
Location	Pasadena, CA
Year Built	1973
Number of apartment homes | apartment_home	92
Initial Cost, Land	$ 9,693
Initial Cost, Buildings and Improvements	6,818
Costs Capitalized Subsequent to Consolidation	4,975
Land	9,693
Buildings and Improvements	11,793
Total	21,486
Accumulated Depreciation (AD)	(5,990)
Total Cost Net of Accumulated Depreciation	15,496
Encumbrances	$ 20,500
Same Store Sales [Member] | Vivo [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Jun. 30, 2016
Location	Cambridge, MA
Year Built	2015
Number of apartment homes | apartment_home	91
Initial Cost, Land	$ 6,450
Initial Cost, Buildings and Improvements	35,974
Costs Capitalized Subsequent to Consolidation	6,054
Land	6,450
Buildings and Improvements	42,028
Total	48,478
Accumulated Depreciation (AD)	(14,322)
Total Cost Net of Accumulated Depreciation	34,156
Encumbrances	$ 19,297
Same Store Sales [Member] | Waterways Village [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Jun. 30, 1997
Location	Aventura, FL
Year Built	1994
Number of apartment homes | apartment_home	180
Initial Cost, Land	$ 4,504
Initial Cost, Buildings and Improvements	11,064
Costs Capitalized Subsequent to Consolidation	16,798
Land	4,504
Buildings and Improvements	27,862
Total	32,366
Accumulated Depreciation (AD)	(15,034)
Total Cost Net of Accumulated Depreciation	17,332
Encumbrances	$ 0
Same Store Sales [Member] | Waverly Apartments [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Aug. 31, 2008
Location	Brighton, MA
Year Built	1970
Number of apartment homes | apartment_home	103
Initial Cost, Land	$ 7,920
Initial Cost, Buildings and Improvements	11,347
Costs Capitalized Subsequent to Consolidation	6,860
Land	7,920
Buildings and Improvements	18,207
Total	26,127
Accumulated Depreciation (AD)	(8,447)
Total Cost Net of Accumulated Depreciation	17,680
Encumbrances	$ 0
Same Store Sales [Member] | Windrift [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2001
Location	Oceanside, CA
Year Built	1987
Number of apartment homes | apartment_home	404
Initial Cost, Land	$ 24,960
Initial Cost, Buildings and Improvements	17,590
Costs Capitalized Subsequent to Consolidation	21,022
Land	24,960
Buildings and Improvements	38,612
Total	63,572
Accumulated Depreciation (AD)	(27,153)
Total Cost Net of Accumulated Depreciation	36,419
Encumbrances	$ 71,199
Same Store Sales [Member] | Windsor Park [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2001
Location	Woodbridge, VA
Year Built	1987
Number of apartment homes | apartment_home	220
Initial Cost, Land	$ 4,279
Initial Cost, Buildings and Improvements	15,970
Costs Capitalized Subsequent to Consolidation	5,437
Land	4,279
Buildings and Improvements	21,407
Total	25,686
Accumulated Depreciation (AD)	(14,071)
Total Cost Net of Accumulated Depreciation	11,615
Encumbrances	$ 0
Same Store Sales [Member] | Park Towne Place [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Apr. 30, 2000
Location	Philadelphia, PA
Year Built	1959
Number of apartment homes | apartment_home	940
Initial Cost, Land	$ 10,472
Initial Cost, Buildings and Improvements	47,301
Costs Capitalized Subsequent to Consolidation	354,675
Land	10,472
Buildings and Improvements	401,976
Total	412,448
Accumulated Depreciation (AD)	(185,618)
Total Cost Net of Accumulated Depreciation	226,830
Encumbrances	$ 193,163
Same Store Sales [Member] | Villas at Park La Brea, The [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Mar. 31, 2002
Location	Los Angeles, CA
Year Built	2002
Number of apartment homes | apartment_home	250
Initial Cost, Land	$ 8,630
Initial Cost, Buildings and Improvements	48,871
Costs Capitalized Subsequent to Consolidation	20,720
Land	8,630
Buildings and Improvements	69,591
Total	78,221
Accumulated Depreciation (AD)	(37,027)
Total Cost Net of Accumulated Depreciation	41,194
Encumbrances	$ 48,156
Same Store Sales [Member] | One Ardmore | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Apr. 30, 2019
Location	Ardmore, PA
Year Built	2019
Number of apartment homes | apartment_home	110
Initial Cost, Land	$ 4,929
Initial Cost, Buildings and Improvements	61,631
Costs Capitalized Subsequent to Consolidation	1,865
Land	4,929
Buildings and Improvements	63,496
Total	68,425
Accumulated Depreciation (AD)	(3,911)
Total Cost Net of Accumulated Depreciation	64,514
Encumbrances	$ 30,448
Same Store Sales [Member] | SouthStar Lofts [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	May 31, 2018
Location	Philadelphia, PA
Year Built	2014
Number of apartment homes | apartment_home	85
Initial Cost, Land	$ 1,780
Initial Cost, Buildings and Improvements	37,428
Costs Capitalized Subsequent to Consolidation	901
Land	1,780
Buildings and Improvements	38,329
Total	40,109
Accumulated Depreciation (AD)	(3,706)
Total Cost Net of Accumulated Depreciation	36,403
Encumbrances	$ 29,028
Same Store Sales [Member] | The Left Bank [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	May 31, 2018
Location	Philadelphia, PA
Year Built	1929
Number of apartment homes | apartment_home	282
Initial Cost, Land	$ 0
Initial Cost, Buildings and Improvements	130,893
Costs Capitalized Subsequent to Consolidation	19,781
Land	0
Buildings and Improvements	150,674
Total	150,674
Accumulated Depreciation (AD)	(14,018)
Total Cost Net of Accumulated Depreciation	136,656
Encumbrances	$ 78,925
Other Real Estate [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of apartment homes | apartment_home	1,391
Initial Cost, Land	$ 144,472
Initial Cost, Buildings and Improvements	42,413
Costs Capitalized Subsequent to Consolidation	589,309
Land	97,191
Buildings and Improvements	631,722
Total	728,913
Accumulated Depreciation (AD)	(111,337)
Total Cost Net of Accumulated Depreciation	617,576
Encumbrances	$ 58,014
Other Real Estate [Member] | 240 West 73rd Street | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Sep. 30, 2004
Location	New York, NY
Year Built	1900
Number of apartment homes | apartment_home	200
Initial Cost, Land	$ 68,109
Initial Cost, Buildings and Improvements	12,140
Costs Capitalized Subsequent to Consolidation	17,138
Land	20,828
Buildings and Improvements	29,278
Total	50,106
Accumulated Depreciation (AD)	(10,568)
Total Cost Net of Accumulated Depreciation	39,538
Encumbrances	$ 0
Other Real Estate [Member] | 236-238 East 88th Street [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Jan. 31, 2004
Location	New York, NY
Year Built	1900
Number of apartment homes | apartment_home	42
Initial Cost, Land	$ 8,820
Initial Cost, Buildings and Improvements	2,914
Costs Capitalized Subsequent to Consolidation	12,311
Land	8,820
Buildings and Improvements	15,225
Total	24,045
Accumulated Depreciation (AD)	(2,195)
Total Cost Net of Accumulated Depreciation	21,850
Encumbrances	$ 0
Other Real Estate [Member] | 707 Leahy [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Apr. 30, 2007
Location	Redwood City, CA
Year Built	1973
Number of apartment homes | apartment_home	110
Initial Cost, Land	$ 15,444
Initial Cost, Buildings and Improvements	7,909
Costs Capitalized Subsequent to Consolidation	35,135
Land	15,444
Buildings and Improvements	43,044
Total	58,488
Accumulated Depreciation (AD)	(7,630)
Total Cost Net of Accumulated Depreciation	50,858
Encumbrances	$ 0
Other Real Estate [Member] | Eldridge Townhomes [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Town Home
Date Consolidated	Sep. 30, 2017
Location	Elmhurst, IL
Year Built	2018
Number of apartment homes | apartment_home	58
Initial Cost, Land	$ 3,105
Initial Cost, Buildings and Improvements	0
Costs Capitalized Subsequent to Consolidation	30,998
Land	3,105
Buildings and Improvements	30,998
Total	34,103
Accumulated Depreciation (AD)	(614)
Total Cost Net of Accumulated Depreciation	33,489
Encumbrances	$ 0
Other Real Estate [Member] | Fremont [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Mid Rise
Date Consolidated	Sep. 30, 2018
Location	Denver, CO
Year Built	2020
Number of apartment homes | apartment_home	253
Initial Cost, Land	$ 1,830
Initial Cost, Buildings and Improvements	0
Costs Capitalized Subsequent to Consolidation	89,196
Land	1,830
Buildings and Improvements	89,196
Total	91,026
Accumulated Depreciation (AD)	(1,215)
Total Cost Net of Accumulated Depreciation	89,811
Encumbrances	$ 0
Other Real Estate [Member] | Flamingo Point, North Tower [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	High Rise
Date Consolidated	Sep. 30, 1997
Location	Miami Beach, FL
Year Built	1960
Number of apartment homes | apartment_home	366
Initial Cost, Land	$ 17,248
Initial Cost, Buildings and Improvements	19,450
Costs Capitalized Subsequent to Consolidation	217,222
Land	17,248
Buildings and Improvements	236,672
Total	253,920
Accumulated Depreciation (AD)	(82,561)
Total Cost Net of Accumulated Depreciation	171,359
Encumbrances	$ 0
Other Real Estate [Member] | Parc Mosaic [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Apartment Type	Garden
Date Consolidated	Dec. 31, 2014
Location	Boulder, CO
Year Built	1970
Number of apartment homes | apartment_home	226
Initial Cost, Land	$ 15,300
Initial Cost, Buildings and Improvements	0
Costs Capitalized Subsequent to Consolidation	109,626
Land	15,300
Buildings and Improvements	109,626
Total	124,926
Accumulated Depreciation (AD)	(6,554)
Total Cost Net of Accumulated Depreciation	118,372
Encumbrances	$ 58,014
Other Real Estate [Member] | Other [Member] | Continuing Operations [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of apartment homes | apartment_home	136
Initial Cost, Land	$ 14,616
Initial Cost, Buildings and Improvements	0
Costs Capitalized Subsequent to Consolidation	77,683
Land	14,616
Buildings and Improvements	77,683
Total	92,299
Accumulated Depreciation (AD)	0
Total Cost Net of Accumulated Depreciation	92,299
Encumbrances	$ 0

Schedule III_ Real Estate and_2

Schedule III: Real Estate and Accumulated Depreciation - Schedule of Real Estate and Accumulated Depreciation (Parenthetical) (Details) $ in Billions	12 Months Ended
	Dec. 31, 2020USD ($)
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Aggregate cost of land and depreciable property for federal income tax purposes	$ 4
Minimum [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Depreciable life for buildings and improvements	5 years
Maximum [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Depreciable life for buildings and improvements	30 years

Schedule III_ Real Estate and_3

Schedule III: Real Estate and Accumulated Depreciation - Summary Real Estate and Accumulated Depreciation (Details) - AIR Real Estate [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Total portfolio
Total portfolio balance at beginning of year	$ 7,351,979	$ 7,338,906	$ 7,488,019
Additions during the year:
Acquisitions	6,062	81,344	501,009
Capital additions	329,156	368,133	310,452
Dispositions and other	(218,333)	(436,404)	(960,574)
Total portfolio balance at end of year	7,468,864	7,351,979	7,338,906
Accumulated depreciation balance at beginning of year	2,268,839	2,228,533	2,504,193
Depreciation	310,400	308,905	320,664
Dispositions and other	(123,734)	(268,599)	(596,324)
Accumulated depreciation balance at end of year	$ 2,455,505	$ 2,268,839	$ 2,228,533