Debt (Details)				9 Months Ended		0 Months Ended			0 Months Ended	9 Months Ended			0 Months Ended			0 Months Ended			0 Months Ended			9 Months Ended
	Sep. 30, 2014 USD ($) item	Dec. 31, 2013 USD ($)	Sep. 30, 2014 Line of Credit and Term Loan	Sep. 30, 2014 Bank Line of Credit USD ($)	Mar. 31, 2014 Bank Line of Credit USD ($)	Jul. 30, 2012 2012 Term Loan GBP (£)	Sep. 30, 2014 2012 Term Loan USD ($)	Sep. 30, 2014 2012 Term Loan GBP (£)	Jul. 30, 2012 2012 Term Loan Interest-rate swap contracts	Sep. 30, 2014 Senior Unsecured Notes USD ($)	Sep. 30, 2014 Senior Unsecured Notes Minimum	Sep. 30, 2014 Senior Unsecured Notes Maximum	Aug. 14, 2014 Senior Unsecured, 3.875% notes due 2024[Member] USD ($)	Aug. 14, 2014 Senior Unsecured, 3.875% notes due 2024[Member] USD ($)	Aug. 07, 2014 Senior Unsecured, 3.875% notes due 2024[Member]	Feb. 12, 2014 Senior Unsecured, 4.20% notes due 2024 USD ($)	Feb. 01, 2014 Senior unsecured notes, 2.7% USD ($)	Feb. 01, 2014 Senior unsecured notes, 2.7%	Dec. 16, 2013 Senior unsecured notes, 5.65% USD ($)	Nov. 12, 2013 Senior Unsecured, 4.25% notes due 2023 USD ($)	Feb. 28, 2013 Senior Unsecured, 5.625% USD ($)	Sep. 30, 2014 Mortgage Debt USD ($) item	Sep. 30, 2014 Mortgage Debt Minimum	Sep. 30, 2014 Mortgage Debt Maximum	Sep. 30, 2014 Demand Note USD ($)	Sep. 30, 2014 Non-interest Bearing Life Care Bonds USD ($)
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
Bank line of credit	70,000,000			70,000,000
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
Debt instrument, effective interest rate (as a percent)															3.92%	4.257%				4.307%
Weighted-average interest rate (as a percent)				1.34%						4.95%												6.21%
Weighted-average maturity										6 years												3 years
Issuance of senior unsecured notes														800,000,000		350,000,000				800,000,000
Debt issuance price as a percentage of principal amount														99.63%		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													792,000,000			346,000,000				789,000,000
Stated interest rate (as a percent)											2.79%	6.99%		3.875%		4.20%		2.70%	5.65%	4.25%	5.625%		0.44%	8.69%	4.50%
2014 (Six months)	249,052,000																					249,052,000
2015	440,164,000									400,000,000												40,164,000
2016	1,413,854,000						222,118,000			900,000,000												291,736,000
2017	1,300,477,000									750,000,000												550,477,000
2018	676,583,000			70,000,000						600,000,000												6,583,000
Thereafter	5,065,242,000									5,000,000,000												65,242,000
Total debt before discount, net	9,145,372,000			70,000,000			222,118,000			7,650,000,000												1,203,254,000
Discounts, net	(28,580,000)									(24,959,000)												(3,621,000)
Debt instruments, carrying amount	9,116,792,000			70,000,000		137,000,000	222,118,000	137,000,000		7,625,041,000												1,199,633,000
Number of healthcare facilities used to secure debt																						88
Debt instrument, collateral, healthcare facilities carrying value																						1,400,000,000
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	$ 97,845,000	$ 74,909,000																							$ 26,000,000	$ 72,000,000
Number of CCRC issuing non-interest life care bonds	2
Number of facilities with non-interest bearing occupancy fee deposits	2