Finance Receivables - Internal Credit Quality Rating (Details) $ in Thousands	Dec. 31, 2020 USD ($) tenant	Dec. 31, 2019 USD ($) tenant
Credit Quality Of Finance Receivables
Net investments in direct financing leases	$ 765,784	$ 944,286
Internally Assigned Grade1 thru 3
Credit Quality Of Finance Receivables
Number of tenants (tenant) | tenant	18	28
Net investments in direct financing leases	$ 587,103	$ 798,108
Internally Assigned Grade 4
Credit Quality Of Finance Receivables
Number of tenants (tenant) | tenant	9	8
Net investments in direct financing leases	$ 141,944	$ 146,178
Internally Assigned Grade 5
Credit Quality Of Finance Receivables
Number of tenants (tenant) | tenant	2	0
Net investments in direct financing leases	$ 36,737	$ 0