Leases (Narrative) (Details) - lease |
Mar. 31, 2019 |
Jan. 01, 2019 |
Dec. 31, 2018 |
|---|---|---|---|
| Lessee, Lease, Description [Line Items] | |||
| Number of operating ground leases | 6 | 3 | |
| Number of operating ground leases without corresponding operating lease liabilities | 3 | ||
| Operating lease, weighted average remaining lease term | 78 years 1 month 6 days | 52 years | |
| Minimum [Member] | |||
| Lessee, Lease, Description [Line Items] | |||
| Operating lease, weighted average incremental borrowing rate, percent | 5.60% | ||
| Maximum [Member] | |||
| Lessee, Lease, Description [Line Items] | |||
| Operating lease, weighted average incremental borrowing rate, percent | 6.60% |