Significant Transactions During the First Quarter of 2017 and Subsequent Event (Details)	1 Months Ended			3 Months Ended
	Apr. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) unit project	Jan. 31, 2017 USD ($) community unit	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Other Commitments [Line Items]
Payments to acquire preferred equity investments				$ 120,816,000	$ 50,591,000
Gain on remeasurement of co-investment				86,482,000	$ 0
Co-investments		$ 1,071,258,000		1,071,258,000		$ 1,161,275,000
Land and land improvements		2,719,064,000		2,719,064,000		2,559,743,000
Buildings and improvements		10,492,413,000		10,492,413,000		10,116,563,000
Prepaid expenses and other assets		53,716,000		53,716,000		48,450,000
Senior Notes [Member] | Senior Unsecured Notes at 5.500% [Member]
Other Commitments [Line Items]
Senior unsecured notes paid off		$ 300,000,000		$ 300,000,000
Stated interest rate (as a percent)		5.50%		5.50%
Subsequent Event [Member] | Senior Notes [Member] | Senior Unsecured Notes At 3.625% [Member]
Other Commitments [Line Items]
Stated interest rate (as a percent)	3.625%
Debt instrument, face amount	$ 350,000,000
Debt instrument, term (in years)	10 years
Membership Interest In Palm Valley And Sage At Cupertino [Member]
Other Commitments [Line Items]
Land and land improvements		$ 169,500,000		$ 169,500,000
Buildings and improvements		365,700,000		365,700,000
Prepaid expenses and other assets		$ 3,200,000		3,200,000
Membership Interest In Palm Valley [Member]
Other Commitments [Line Items]
Equity method investment, ownership percentage acquired (as a percent)			50.00%
Payments to acquire preferred equity investments			$ 183,000,000
Mortgage encumbrance						$ 220,000,000
Number of units acquired (in units) | unit			1,098
Number of communities acquired (in communities) | community			4
Gain on remeasurement of co-investment			$ 86,500,000
Membership Interest In Sage At Cupertino [Member]
Other Commitments [Line Items]
Equity method investment, ownership percentage acquired (as a percent)		40.50%
Mortgage encumbrance		$ 52,000,000		52,000,000
Number of units acquired (in units) | unit		230
Co-investments		$ 15,300,000		15,300,000
Contract price		90,000,000
Jefferson at Hollywood [Member]
Other Commitments [Line Items]
Number of units sold (in units) | unit			270
Proceeds from sale of real estate			$ 132,500,000
Gain (loss) on sale of properties			$ 26,200,000
Limited Liability Company with Development Projects in Fullerton and Irvine, CA [Member] | Equity Method Investments [Member]
Other Commitments [Line Items]
Payments to acquire preferred equity investments		2,000,000
Co-investments		$ 21,500,000		$ 21,500,000
Number of development projects (in projects) | project		2
Preferred equity investment, dividend rate, first 30 months (as a percent)		11.00%
Preferred equity investment, dividend rate, after 30 months (as a percent)		9.50%
Limited Liability Company with Development Projects in Fullerton and Irvine, CA [Member] | Equity Method Investments [Member] | Fullerton, CA [Member]
Other Commitments [Line Items]
Number of units acquired (in units) | unit		142
Limited Liability Company with Development Projects in Fullerton and Irvine, CA [Member] | Equity Method Investments [Member] | Irvine, CA [Member]
Other Commitments [Line Items]
Number of units acquired (in units) | unit		170