Other Assets (Details) $ in Thousands, £ in Millions	1 Months Ended			12 Months Ended
	Dec. 31, 2015 GBP (£) item	Dec. 31, 2015 USD ($)	Jun. 30, 2012 GBP (£)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)	Jun. 30, 2012 USD ($)
Other assets
Straight-line rent receivables, net of allowance of $33,648 and $34,182, respectively					$ 385,888	$ 355,864
Allowance on straight-line rent receivables					33,648	34,182
Marketable debt securities, net					102,958	231,442
Leasing costs and inducements, net					158,708	146,500
Goodwill					50,346	50,346
Other					119,965	117,516
Total other assets					817,865	901,668
Loans receivables					768,743	906,961
Realized gains on marketable debt securities sold				$ 11,000
Brookdale Senior Living
Other assets
Loans receivables					$ 9,000	26,000
Number of installments | item	8				8
Four Seasons
Other assets
Marketable debt securities, net	£ 58.0				$ 85,000
Loan receivable, interest rate payable (as a percent)			12.25%				12.25%
Marketable debt security, par value	28.0		£ 138.5		$ 42,000
Marketable debt security, par value, discounted			£ 136.8				$ 215,000
Marketable debt security, issed and outstanding as a percentage			79.00%
Marketable debt security, issued and outstanding | £	40.0		£ 175.0
Interest payment received	£ 8.0	$ 13,000
HCP Ventures IV
Other assets
Loans receivables						$ 15,000