Noncontrolling Interests (Narrative) (Details)		3 Months Ended		6 Months Ended
	Jan. 01, 2018 USD ($)	Jun. 30, 2019 USD ($) shares	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) property shares	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Noncontrolling Interests [Line Items]
Common units in operating partnership | shares				7,305,355
Noncontrolling interests		$ 216,327,000		$ 216,327,000		$ 218,091,000
Number of units in multi-family asset | property				395
Number of shares of common stock for each unit of limited partnership interest redeemed | shares		1		1
Net income (loss) allocation to noncontrolling interests		$ 7,623,000	$ 18,400,000	$ 14,650,000	$ 30,300,000
Noncontrolling interest in consolidated joint venture					4,032,000
Net income allocation to noncontrolling interests - common units		7,613,000	18,783,000	14,637,000	31,119,000
Distribution paid		45,000	0	45,000	0
PS [Member]
Noncontrolling Interests [Line Items]
Noncontrolling interests		213,400,000		213,400,000		215,100,000
JV Partner [Member]
Noncontrolling Interests [Line Items]
Noncontrolling interests		$ 3,000,000.0		$ 3,000,000.0		$ 3,000,000.0
Economic interest in joint venture, percentage		5.00%		5.00%
Net income (loss) allocation to noncontrolling interests		$ 10,000	$ (383,000)	$ 13,000	$ (819,000)
Noncontrolling interest in consolidated joint venture	$ 4,032,000