Significant Transactions During the Three Months Ended March 31, 2019 and Subsequent Events (Details) - USD ($)	1 Months Ended				3 Months Ended
	Apr. 30, 2019	Mar. 31, 2019	Feb. 28, 2019	Jan. 31, 2019	Mar. 31, 2019	Mar. 31, 2018	Feb. 19, 2019
Other Commitments [Line Items]
Repayments of secured debt		$ 86,000,000		$ 290,000,000
Gain on remeasurement of co-investment		31,500,000			$ 31,535,000	$ 0
Promote income		800,000
Proceeds from full redemption of a preferred equity investment in a joint venture			$ 10,900,000
Early redemption fee			100,000
Shares repurchased during period (in shares)				234,061
Shares repurchased during period, value				$ 57,000,000
Purchase authority remaining under stock repurchase plan		250,000,000			250,000,000		$ 250,000,000
Debt, stated interest rate				5.57%
Gain on early retirement of debt, net				$ 1,400,000	1,336,000	$ 0
Subsequent Event [Member]
Other Commitments [Line Items]
Proceeds from full redemption of a preferred equity investment in a joint venture	$ 16,300,000
Senior Notes [Member] | Unsecured Notes, 4.0 Interest Rate, Due March 2029 [Member]
Other Commitments [Line Items]
Debt, face amount		$ 150,000,000.0	$ 350,000,000.0		$ 150,000,000.0
Debt, stated interest rate			4.00%
Debt offering price, percentage of par value		100.717%	99.188%		100.717%
Multifamily Development Community in Irvine, CA [Member]
Other Commitments [Line Items]
Commitment to fund preferred equity investment		$ 36,000,000			$ 36,000,000
Preferred returns rate		10.15%
Multifamily Development in Mountain View, California
Other Commitments [Line Items]
Commitment to fund preferred equity investment			$ 24,500,000
Preferred returns rate			11.00%
One South Market, San Jose, CA [Member]
Other Commitments [Line Items]
Limited partnership interest in partnership investments		45.00%
Payments to joint venture interest		$ 80,600,000