Segment Information (Assets and Capital Expenditures) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012		Dec. 31, 2011
Assets
Total assets	$ 19,731,494,000	$ 18,980,000,000
Percentage of total assets	100.00%	100.00%
Capital expenditures
Capital Expenditures	1,614,357,000	1,901,916,000		629,669,000
Triple Net Leased Properties
Assets
Total assets	8,919,360,000	8,368,186,000
Percentage of total assets	45.20%	44.10%
Capital expenditures
Capital Expenditures	847,945,000	139,680,000	[1]	133,761,000
Capital expenditures from funds held in Code Section 1031 exchange escrow account		58,100,000
Senior Living Operations
Assets
Total assets	6,648,754,000	6,274,207,000
Percentage of total assets	33.70%	33.10%
Capital expenditures
Capital Expenditures	576,459,000	758,371,000	[1]	370,455,000
Capital expenditures from funds held in Code Section 1031 exchange escrow account		64,700,000
MOB Operations
Assets
Total assets	3,701,344,000	3,703,453,000
Percentage of total assets	18.80%	19.50%
Capital expenditures
Capital Expenditures	189,953,000	1,003,865,000	[1]	125,453,000
Capital expenditures from funds held in Code Section 1031 exchange escrow account		11,200,000
All Other
Assets
Total assets	$ 462,036,000	$ 634,154,000
Percentage of total assets	2.30%	3.30%

[1] Includes funds held in a Code Section 1031 exchange escrow account with a qualified intermediary as follows: triple-net leased – $58.1 million; senior living – $64.7 million; and MOB – $11.2 million.