Archstone Acquisition (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended			0 Months Ended	10 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 27, 2013	Dec. 31, 2013
Business Acquisition Additional Disclosure
Acquisition related expenses recognized									$ (7,681)	$ 44,052	$ 9,593
Equity in income (loss) of unconsolidated entities									148,766	(11,154)	20,914
Information for acquisition that is included in condensed consolidated statement of operations comprehensive income from the acquisition date
Revenues	440,656	430,525	413,806	400,075	394,169	389,189	378,207	301,356	1,685,061	1,462,921	1,000,627
Net income attributable to common stockholders	142,642	241,100	158,086	141,739	252,212	(10,715)	36,218	75,427	683,567	353,141	423,869
Supplemental consolidated pro forma information
Revenues										1,534,868	1,411,504
Income from continuing operations										348,160	158,738
Earnings per common share - diluted (from continuing operations) (in dollars per share)										$ 2.67	$ 1.22
Archstone
Archstone acquisition
Percentage of assets and liabilities acquired												40.00%
Land and land improvements												1,745,520
Buildings and improvements												3,711,853
FF&E												52,290
Construction-in-progress, including land and land held for development (1)												401,747
In-place lease intangibles												182,467
Other assets												109,717
Total consolidated assets												6,203,594
Interest in unconsolidated real estate entities												276,954
Total assets												6,480,548
Fair value of assumed mortgage notes payable												3,732,980
Liability for preferred obligations												67,493
Other liabilities												31,984
Noncontrolling interest												13,262
Net assets acquired												2,634,829
Common shares issued												1,875,210
Cash consideration												759,619
Business Acquisition Additional Disclosure
Acquisition related expenses recognized										83,594
Equity in income (loss) of unconsolidated entities										39,543
Consideration
Number of shares issued										14,889,706		14,889,706
Common shares issued												1,875,210
Cash consideration												759,619
Fair value of indebtedness assumed												3,732,980
Principal amount of consolidated indebtedness					3,512,202					3,512,202		3,512,202	3,512,202
Debt fair value exceeds the principal face value												220,777
Debt fair value exceeds the principal face value relating to debt repaid												70,479
Redemption value of preferred equity					67,500					67,500		67,500	67,500
Information for acquisition that is included in condensed consolidated statement of operations comprehensive income from the acquisition date
Revenues													353,427
Net income attributable to common stockholders													$ (105,589)
Archstone | Equity
Archstone acquisition
Percentage of assets and liabilities acquired												60.00%