Debt (Details)				0 Months Ended				0 Months Ended	3 Months Ended			0 Months Ended					3 Months Ended
	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Mar. 31, 2014 Line of Credit and Term Loan	Mar. 31, 2014 Bank Line of Credit USD ($)	Jul. 30, 2012 2012 Term Loan GBP (£)	Mar. 31, 2014 2012 Term Loan USD ($)	Mar. 31, 2014 2012 Term Loan GBP (£)	Jul. 30, 2012 2012 Term Loan Interest-rate swap contracts	Mar. 31, 2014 Senior Unsecured Notes USD ($)	Mar. 31, 2014 Senior Unsecured Notes Minimum	Mar. 31, 2014 Senior Unsecured Notes Maximum	Feb. 12, 2014 Senior Unsecured, 4.20% notes due 2024 USD ($)	Nov. 12, 2013 Senior Unsecured, 4.25% notes due 2023 USD ($)	Feb. 01, 2014 Senior unsecured notes, 2.7% USD ($)	Dec. 16, 2013 Senior unsecured notes, 5.65% USD ($)	Feb. 28, 2013 Senior Unsecured, 5.625% USD ($)	Mar. 31, 2014 Mortgage Debt USD ($) item	Mar. 31, 2014 Mortgage Debt Minimum	Mar. 31, 2014 Mortgage Debt Maximum	Mar. 31, 2014 Other Debt USD ($) item
Debt Instrument
Increased maximum borrowing capacity				$ 500,000,000
Line of credit facility, maximum borrowing capacity				2,000,000,000
Length of debt instrument extension period				1 year	1 year
Debt instrument, variable rate basis				LIBOR	GBP LIBOR
Debt instrument, basis spread on variable rate (as a percent)				0.925%	1.20%
Debt instrument, facility fee (as a percent)				0.15%
Line of credit facility additional aggregate amount, maximum				500,000,000
Line of credit facility, amount drawn				0
Debt instrument, covenant debt to assets (as a percent)			60.00%
Debt instrument, covenant secured debt to assets (as a percent)			30.00%
Debt instrument, covenant unsecured debt to unencumbered assets (as a percent)			60.00%
Debt instrument, covenant minimum fixed charge coverage ratio			1.5
Debt instrument, covenant net worth				9,500,000,000		9,200,000,000
Debt instrument principal outstanding									6,900,000,000
Debt instrument, effective interest rate (as a percent)												4.257%	4.307%
Weighted-average interest rate (as a percent)									5.06%								6.19%
Weighted-average maturity									6 years								3 years
Issuance of senior unsecured notes												350,000,000	800,000,000
Debt issuance price as a percentage of principal amount												99.537%	99.54%
Repayment of senior unsecured notes														400,000,000	400,000,000	150,000,000
Net proceeds from issuance of senior unsecured notes												346,000,000	789,000,000
Stated interest rate (as a percent)										1.20%	6.99%	4.20%	4.25%	2.70%	5.65%	5.625%		0.69%	8.69%
2014 (Nine months)	104,597,000								87,000,000								17,597,000
2015	708,421,000								400,000,000								308,421,000
2016	1,420,007,000					228,269,000			900,000,000								291,738,000
2017	1,300,477,000								750,000,000								550,477,000
2018	606,583,000								600,000,000								6,583,000
Thereafter	4,265,242,000								4,200,000,000								65,242,000
(Discounts) and premiums, net	(29,077,000)								(24,188,000)								(4,889,000)
Debt instruments, carrying amount	8,376,250,000				137,000,000	228,269,000	137,000,000		6,912,812,000								1,235,169,000
Number of healthcare facilities used to secure debt																	95
Debt instrument, collateral, healthcare facilities carrying value																	1,500,000,000
Maturity period of debt instruments					4 years
Term of the interest rate swap agreement								4 years
Debt instrument, fixed interest rate (as a percent)								1.81%
Portion of other debt and occupancy fee deposits excluded from schedule of debt maturities	$ 74,097,000	$ 74,909,000																		$ 74,000,000
Number of CCRC issuing non-interest life care bonds																				2
Non-interest bearing occupancy fee deposits																				2