Leases - Lease Obligations (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Minimum Rental Revenues
2018	$ 165,893
2019	163,576
2020	149,453
2021	130,834
2022	111,958
Thereafter	514,271
Total	1,235,985
Minimum Rental Payments
2018	4,540
2019	4,560
2020	4,356
2021	4,302
2022	4,395
Thereafter	185,014
Total	$ 207,167