Significant Transactions During the Nine Months Ended September 30, 2022 and Subsequent Events (Details) $ / shares in Units, $ in Thousands	1 Months Ended									3 Months Ended				9 Months Ended
	Oct. 27, 2022 USD ($) apartment	Sep. 30, 2022 USD ($) community	Aug. 31, 2022 USD ($)	Jul. 31, 2022 USD ($) apartment	Jun. 30, 2022 USD ($)	Apr. 30, 2022 USD ($)	Feb. 28, 2022 USD ($)	Jan. 31, 2022 USD ($) apartment	Nov. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) investment community $ / shares shares	Jun. 30, 2022 USD ($) $ / shares shares	Mar. 31, 2022 USD ($) investment	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) community	Sep. 30, 2021 USD ($)	Oct. 22, 2022 USD ($)	Dec. 31, 2021 USD ($)
Other Commitments [Line Items]
Apartment communities owned (in communities) | community		253								253				253
Gain on remeasurement of co-investment				$ 17,400						$ 17,423			$ 0	$ 17,423	$ 2,260
Number of preferred equity investments | investment										4
Commitments to acquire equity method investment										$ 55,400
Preferred return rate										9.50%
Shares repurchased and retired during period (in shares) | shares											218,960
Shares repurchased and retired during period, value										$ 97,100	$ 60,800
Treasury stock acquired, average cost per share (in dollars per share) | $ / shares										$ 261.16	$ 277.81
Purchase authority remaining under stock repurchase plan					$ 153,600						$ 153,600
Stock repurchase plan amount					250,000						250,000
Unsecured debt, net		$ 5,312,131								$ 5,312,131				5,312,131			$ 5,307,196
Stock Repurchase Plan
Other Commitments [Line Items]
Shares repurchased and retired during period (in shares) | shares										371,884
Purchase authority remaining under stock repurchase plan		430,100								$ 430,100				430,100
Stock repurchase plan amount		500,000								$ 500,000				$ 500,000
Stock Repurchase Plan, December 2015
Other Commitments [Line Items]
Shares repurchased and retired during period (in shares) | shares										100,487
Shares repurchased and retired during period, value										$ 27,200
Stock Repurchase Plan, September 2022.
Other Commitments [Line Items]
Shares repurchased and retired during period (in shares) | shares										271,397
Shares repurchased and retired during period, value										$ 69,900
Stock repurchase plan amount					500,000						$ 500,000
Subsequent Event | SOFR
Other Commitments [Line Items]
Basis spread on variable rate	0.85%
Subsequent Event | Term loan - variable rate
Other Commitments [Line Items]
Unsecured debt, net																$ 300,000
Subsequent Event | Term Loan
Other Commitments [Line Items]
Interest rate																4.20%
Number of extension options (in extensions) | apartment	3
Extension period	12 months
Related Party Bridge Loan on Property In Vista, CA
Other Commitments [Line Items]
Proceeds from redemption of notes receivable								$ 48,500
Mezzanine Loans | Subsequent Event
Other Commitments [Line Items]
Receivable with imputed interest, face amount	$ 32,100
Receivable with imputed interest, effective yield (interest rate)	11.30%
Option to extend	2 years
Affiliated Entity
Other Commitments [Line Items]
Notes receivable			$ 11,200
Interest rate			9.50%
Affiliated Entity | Loan on Multifamily Community in Washington
Other Commitments [Line Items]
Notes receivable			$ 10,000
Interest rate			12.00%
Affiliated Entity | Related Party Bridge Loan on Property In Vista, CA
Other Commitments [Line Items]
Notes receivable									$ 48,400
Interest rate									2.36%
Affiliated Entity | Related Party Bridge Loan On Property Acquired By BEX II
Other Commitments [Line Items]
Notes receivable							$ 32,800		$ 32,800
Interest rate							1.35%		1.35%
Joint Venture Partner Essex JV, LLC | Regency Palm Court and Windsor Court
Other Commitments [Line Items]
Investment interest acquired				49.80%
Apartment communities owned (in communities) | apartment				2
Number of units acquired | apartment				211
Payments to acquire real estate				$ 32,900
Wesco IV
Other Commitments [Line Items]
Limited partnership interest in partnership investments						65.10%
Promote interest						$ 37,500
Preferred Equity Investment Property in Southern California and Washington
Other Commitments [Line Items]
Number of preferred equity investments | investment												3
Commitments to acquire equity method investment												$ 29,500
Preferred return rate												10.00%
Joint Venture That Holds Property In California
Other Commitments [Line Items]
Proceeds from dispositions of co-investments												$ 106,900
Early redemption fee												$ 900
Number of preferred equity investments fully redeemed | investment												2
Number of preferred equity investments partially redeemed | investment												2
Preferred Equity Investment Property In Northern California
Other Commitments [Line Items]
Proceeds from dispositions of co-investments		$ 8,400			$ 3,000
Vela On Ox | Affiliated Entity | Related Party Bridge Loan on Property Acquired By Wesco VI
Other Commitments [Line Items]
Notes receivable								$ 100,700
Interest rate								2.64%
Proceeds from redemption of notes receivable								$ 121,300
Vela On Ox | Wesco VI
Other Commitments [Line Items]
Payments to acquire real estate								$ 183,000
Vela On Ox | Apartment Building | Wesco VI
Other Commitments [Line Items]
Number of units acquired | apartment								379