Borrowings Under Credit Facilities and Related Items (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2015 properties		Dec. 31, 2014	Mar. 31, 2014
Line Of Credit Facility [Line Items]
Unsecured line of credit arrangement	$ 2,500,000,000
Additional unsecured line of credit arrangement	1,000,000,000
Number of banks in consortium	28
Available to borrow in alternate currencies	500,000,000
Agent bank's prime rate of interest	1.103%
Interest Rate margin	0.925%
Annual facility fee for each bank based on commitment amount	0.15%
Debt instrument maturity date	Oct. 31, 2018
Balance outstanding at quarter end	410,000,000	[1]	0	562,000,000	[1]
Term Loan Interest Rate Margin	0.975%
HCN Term Loan	500,000,000
HCN Canadian Denomiated Term Loan	250,000,000
Borrowings under primary unsecured credit facilities, Carrying Value	410,000,000	[1]	0	562,000,000	[1]
Financial Stand by Letter Of Credit [Member]
Line Of Credit Facility [Line Items]
Balance outstanding at quarter end	65,335,000
Borrowings under primary unsecured credit facilities, Carrying Value	$ 65,335,000

[1] (1) As of March 31, 2015, letters of credit in the aggregate amount of $65,335,000 have been issued, which reduces the borrowing capacity on the unsecured revolving credit facility.