Leases - Internal Ratings For Net Investment, DFL (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investment [Line Items]
Net investment in direct financing leases	$ 713,818	$ 714,352
Percentage of DFL Portfolio	100.00%
Senior housing triple-net
Investment [Line Items]
Net investment in direct financing leases	$ 629,214
Percentage of DFL Portfolio	88.00%
Other non-reportable segments
Investment [Line Items]
Net investment in direct financing leases	$ 84,604
Percentage of DFL Portfolio	12.00%
Performing Loans
Investment [Line Items]
Net investment in direct financing leases	$ 363,107
Performing Loans | Senior housing triple-net
Investment [Line Items]
Net investment in direct financing leases	278,503
Performing Loans | Other non-reportable segments
Investment [Line Items]
Net investment in direct financing leases	84,604
Watch List Loans
Investment [Line Items]
Net investment in direct financing leases	350,711
Watch List Loans | Senior housing triple-net
Investment [Line Items]
Net investment in direct financing leases	350,711
Watch List Loans | Other non-reportable segments
Investment [Line Items]
Net investment in direct financing leases	0
Workout DFLs
Investment [Line Items]
Net investment in direct financing leases	0
Workout DFLs | Senior housing triple-net
Investment [Line Items]
Net investment in direct financing leases	0
Workout DFLs | Other non-reportable segments
Investment [Line Items]
Net investment in direct financing leases	$ 0