Debt (Details)	0 Months Ended										0 Months Ended		12 Months Ended					0 Months Ended					0 Months Ended				12 Months Ended									0 Months Ended		0 Months Ended		0 Months Ended					12 Months Ended									0 Months Ended
	Jan. 01, 2015	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2014 Debt maturing in 2015 USD ($)	Dec. 31, 2014 Debt maturing in 2016 USD ($)	Dec. 31, 2014 Debt maturing in 2017 USD ($)	Dec. 31, 2014 Debt maturing in 2018 USD ($)	Dec. 31, 2014 Debt maturing in 2019 USD ($)	Dec. 31, 2014 Thereafter USD ($)	Dec. 31, 2014 Line of Credit and Term Loan USD ($)	Jan. 21, 2015 Bank Line of Credit USD ($)	Jan. 12, 2015 Bank Line of Credit GBP (£)	Dec. 31, 2014 Bank Line of Credit USD ($)	Jan. 31, 2015 Bank Line of Credit GBP (£)	Dec. 31, 2014 Bank Line of Credit GBP (£)	Mar. 31, 2014 Bank Line of Credit USD ($)	Dec. 31, 2014 Bank Line of Credit Debt maturing in 2018 USD ($)	Jul. 30, 2012 2012 Term Loan GBP (£)	Dec. 31, 2014 2012 Term Loan USD ($)	Dec. 31, 2014 2012 Term Loan GBP (£)	Dec. 31, 2013 2012 Term Loan USD ($)	Dec. 31, 2014 2012 Term Loan Debt maturing in 2016 USD ($)	Jul. 30, 2012 2012 Term Loan Interest-rate swap contracts	Jan. 12, 2015 2015 Term Loan [Member]	Jan. 12, 2015 2015 Term Loan [Member] USD ($)	Jan. 12, 2015 2015 Term Loan [Member] GBP (£)	Dec. 31, 2014 Senior Unsecured Notes USD ($)	Dec. 31, 2014 Senior Unsecured Notes Minimum	Dec. 31, 2014 Senior Unsecured Notes Maximum	Dec. 31, 2014 Senior Unsecured Notes Debt maturing in 2015 USD ($)	Dec. 31, 2014 Senior Unsecured Notes Debt maturing in 2016 USD ($)	Dec. 31, 2014 Senior Unsecured Notes Debt maturing in 2017 USD ($)	Dec. 31, 2014 Senior Unsecured Notes Debt maturing in 2018 USD ($)	Dec. 31, 2014 Senior Unsecured Notes Debt maturing in 2019 USD ($)	Dec. 31, 2014 Senior Unsecured Notes Thereafter USD ($)	Jan. 21, 2015 Senior Unsecured, 3.40% notes due 2025 USD ($)	Jan. 21, 2015 Senior Unsecured, 3.40% notes due 2025 USD ($)	Aug. 14, 2014 Senior Unsecured, 3.875% notes due 2024 USD ($)	Aug. 14, 2014 Senior Unsecured, 3.875% notes due 2024 USD ($)	Feb. 12, 2014 Senior Unsecured, 4.20% notes due 2024 USD ($)	Feb. 01, 2014 Senior unsecured notes, 2.7% USD ($)	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 ($)	Dec. 31, 2014 Mortgage Debt USD ($) item	Dec. 31, 2014 Mortgage Debt Minimum	Dec. 31, 2014 Mortgage Debt Maximum	Dec. 31, 2014 Mortgage Debt Debt maturing in 2015 USD ($)	Dec. 31, 2014 Mortgage Debt Debt maturing in 2016 USD ($)	Dec. 31, 2014 Mortgage Debt Debt maturing in 2017 USD ($)	Dec. 31, 2014 Mortgage Debt Debt maturing in 2018 USD ($)	Dec. 31, 2014 Mortgage Debt Debt maturing in 2019 USD ($)	Dec. 31, 2014 Mortgage Debt Thereafter USD ($)	Aug. 29, 2014 Demand Note USD ($)	Aug. 29, 2014 Demand Note	Dec. 31, 2014 Non-interest Bearing Life Care Bonds USD ($) 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						GBP LIBOR
Debt instrument, basis spread on variable rate (as a percent)													0.925%					1.20%						0.975%
Debt instrument, facility fee (as a percent)													0.15%
Line of credit facility additional aggregate amount, maximum													500,000,000
Bank line of credit		838,516,000											839,000,000	135,000,000	355,000,000
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)																																					3.497%		3.92%	4.257%			4.307%
Weighted-average interest rate (as a percent)													1.60%														4.95%																		6.16%
Weighted-average maturity																											6 years																		3 years
Issuance of senior unsecured notes																																					600,000,000		800,000,000	350,000,000			800,000,000
Debt issuance price as a percentage of principal amount																																					99.185%		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																																				591,000,000		792,000,000		346,000,000			789,000,000											26,000,000
Stated interest rate (as a percent)																											4.95%	2.79%	6.99%	6.57%	5.10%	6.02%	6.82%	3.96%	4.45%		3.40%		3.875%	4.20%	2.70%	5.65%	4.25%	5.625%	6.16%	0.44%	8.41%	3.58%	6.87%	6.07%	5.90%		4.99%		4.50%
2015				440,628,000																										400,000,000																		40,628,000
2016					1,405,832,000															137,000,000		213,610,000									900,000,000																		292,222,000
2017						1,331,891,000																										750,000,000																		581,891,000
2018							1,445,099,000										838,516,000																600,000,000																		6,583,000
2019								452,072,000																										450,000,000																		2,072,000
Thereafter									4,613,170,000																										4,550,000,000																		63,170,000
Total debt before discount, net		9,688,692,000											838,516,000						213,610,000								7,650,000,000																		986,566,000
Discounts, net		(25,941,000)																									(23,806,000)																		(2,135,000)
Debt instruments, carrying amount		9,662,751,000											838,516,000					137,000,000	213,610,000		214,000,000						7,626,194,000																		984,431,000
Number of healthcare facilities used to secure debt																																													70
Debt instrument, collateral, healthcare facilities carrying value																																													1,300,000,000
Maturity period of debt instruments																		4 years						4 years
Term of the interest rate swap agreement	3 years																						4 years
Debt instrument, fixed interest rate (as a percent)																							1.81%		1.79%	1.79%
Portion of other debt and occupancy fee deposits excluded from schedule of debt maturities		97,022,000	74,909,000																																																					71,000,000
Number of CCRC issuing non-interest life care bonds																																																								2
Number of facilities with non-interest bearing occupancy fee deposits																																																								2
Unsecured term loan		7,626,194,000	6,963,375,000																						333,000,000	220,000,000
Repayments of Lines of Credit											$ 105,000,000	£ 220,000,000