Equity (Details)						1 Months Ended		3 Months Ended		9 Months Ended
	Oct. 29, 2015 $ / shares	Oct. 07, 2015 USD ($) property	Jul. 30, 2015 $ / shares	Apr. 30, 2015 $ / shares	Jan. 29, 2015 $ / shares	Oct. 31, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) item $ / shares	Sep. 30, 2015 USD ($) item $ / shares	Sep. 30, 2014 $ / shares	Sep. 30, 2015 USD ($) item $ / shares shares	Sep. 30, 2014 USD ($) $ / shares shares	Dec. 31, 2014 USD ($)
Equity
Common Stock, Dividends, Per Share, Declared | $ / shares			$ 0.565	$ 0.565	$ 0.565			$ 0.565	$ 0.545	$ 1.695	$ 1.635
Company's common stock issuances
Repurchase of common stock										$ 8,006,000	$ 11,599,000
Accumulated Other Comprehensive Loss
Cumulative foreign currency translation adjustment							$ (18,844,000)	$ (18,844,000)		(18,844,000)		$ (10,747,000)
Unrealized losses on cash flow hedges, net							(9,932,000)	(9,932,000)		(9,932,000)		(9,624,000)
Supplemental Executive Retirement Plan minimum liability							(3,329,000)	(3,329,000)		(3,329,000)		(3,537,000)
Unrealized gains on available for sale securities							(345,000)	(345,000)		(345,000)		13,000
Total accumulated other comprehensive loss							(32,450,000)	(32,450,000)		(32,450,000)		(23,895,000)
Noncontrolling interests
DownREIT unit, carrying value							186,133,000	$ 186,133,000		$ 186,133,000		$ 188,588,000
Maximum sales under equity offering program							$ 750,000,000
Common stock issued (in shares) | shares										1,250,000
Weighted average price (in dollars per share) | $ / shares							$ 40.58	$ 40.58		$ 40.58
Proceeds from issuance of common stock										$ 50,000,000
Stock issuance fees and commissions										1,000,000
Payments of Stock Issuance Costs										$ 1,000,000
Subsequent event
Equity
Common Stock, Dividends, Per Share, Declared | $ / shares	$ 0.565
Noncontrolling interests
Common stock issued (in shares) | shares						589,000
Weighted average price (in dollars per share) | $ / shares						$ 39.20
Proceeds from issuance of common stock						$ 23,000,000
Stock issuance fees and commissions						350,000
Payments of Stock Issuance Costs						$ 350,000
HCP Ventures V | Subsequent event
Noncontrolling interests
Noncontrolling interest issued (as a percentage)		49				49
Number of Real Estate Properties | property		11
Consideration received from sale of noncontrolling interest in HCP Ventures V		$ 110,000,000
Common Stock
Company's common stock issuances
Dividend Reinvestment and Stock Purchase Plan (in shares) | shares										2,345,000	1,775,000
Conversion of DownREIT units (in shares) | shares										75,000	2,000
Exercise of stock options (in shares) | shares										820,000	131,000
Vesting of restricted stock units (in shares) | shares										382,000	575,000
Repurchase of common stock										$ 178,000	$ 297,000
Noncontrolling interests
Common stock issued (in shares) | shares										4,054,000	2,351,000
Noncontrolling Interests
Noncontrolling interests
Non-managing members DownREIT units outstanding | item							4,000,000	4,000,000		4,000,000
Number of DownREIT LLCs | item							5	5		5
DownREIT unit, carrying value							$ 186,000,000	$ 186,000,000		$ 186,000,000
DownREIT unit, fair value							$ 224,000,000	$ 224,000,000		$ 224,000,000