Segment Information (Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets
Total assets	$ 24,717,786	$ 23,929,404
Percentage of total assets	100.00%	100.00%
Operating Segments | Triple-net leased properties
Assets
Total assets	$ 4,578,534	$ 5,147,503
Percentage of total assets	18.50%	21.60%
Operating Segments | Senior living operations
Assets
Total assets	$ 12,811,611	$ 10,653,428
Percentage of total assets	51.80%	44.50%
Operating Segments | Office operations
Assets
Total assets	$ 6,341,888	$ 6,709,602
Percentage of total assets	25.70%	28.00%
All Other
Assets
Total assets	$ 985,753	$ 1,418,871
Percentage of total assets	4.00%	5.90%