Segment Information (Assets and Capital Expenditures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Total assets	$ 22,261,918	$ 21,165,913
Percentage of total assets	100.00%	100.00%
Capital expenditures
Capital Expenditures	$ 2,877,949	$ 1,662,728	$ 1,614,357
Operating Segments | Triple-net leased properties
Assets
Total assets	$ 7,996,645	$ 9,115,901
Percentage of total assets	35.90%	43.10%
Capital expenditures
Capital Expenditures	$ 1,890,245	$ 647,870	847,945
Operating Segments | Senior living operations
Assets
Total assets	$ 8,022,206	$ 7,421,924
Percentage of total assets	36.00%	35.10%
Capital expenditures
Capital Expenditures	$ 382,877	$ 977,997	576,459
Operating Segments | MOB operations
Assets
Total assets	$ 5,209,751	$ 3,526,217
Percentage of total assets	23.40%	16.60%
Capital expenditures
Capital Expenditures	$ 604,827	$ 36,861	$ 189,953
All Other
Assets
Total assets	$ 1,033,316	$ 1,101,871
Percentage of total assets	4.70%	5.20%