Other Assets (Details)	9 Months Ended				0 Months Ended
	Sep. 30, 2013 USD ($)	Dec. 31, 2012 USD ($)	Sep. 30, 2013 Delphis USD ($)	Dec. 31, 2012 Delphis USD ($)	Jun. 28, 2012 Four Seasons USD ($)	Jun. 28, 2012 Four Seasons GBP (£)	Sep. 30, 2013 Four Seasons USD ($)	Sep. 30, 2013 Four Seasons GBP (£)	Dec. 31, 2012 Four Seasons USD ($)	Dec. 31, 2012 Four Seasons GBP (£)	Sep. 30, 2013 HCP Ventures IV, LLC USD ($)	Dec. 31, 2012 HCP Ventures IV, LLC USD ($)
Other Assets.
Straight-line rent assets, net of allowance of $34,123 and $33,521, respectively	$ 358,514,000	$ 306,294,000
Allowance on straight-line rent assets	34,123,000	33,521,000
Marketable debt securities, net	238,834,000	222,809,000
Leasing costs, net	98,406,000	93,763,000
Deferred financing costs, net	37,379,000	45,490,000
Goodwill	50,346,000	50,346,000
Marketable equity securities		24,829,000
Other	52,518,000	44,989,000
Total other assets	835,997,000	788,520,000
Cost basis of marketable equity securities		17,100,000
Other assets
Carrying value of interest accrued related to the Delphis loan			0	0
Reserve related to accrued interest receivable			5,400,000	5,400,000
Loans receivables	390,803,000	276,030,000									10,000,000	10,000,000
Loan receivable, interest rate payable (as a percent)					12.25%	12.25%					12.00%	12.00%
Percentage of counter party's partnership interest in the joint venture, by which loans receivable from unconsolidated joint venture are secured											80.00%
Realized gains on marketable debt securities sold	11,000,000
Marketable debt security, par value						138,500,000
Marketable debt security, par value, discounted					$ 214,900,000	£ 136,800,000	$ 222,000,000	£ 137,000,000	$ 223,000,000	£ 137,000,000
Yield to maturity (as a percent)					12.50%	12.50%