Commitments and Contingencies (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Future minimum lease payments due under operating and capital leases
Operating Leases 2018	$ 17,871
Capital Leases 2018	4,678	[1]
Operating Leases 2019	18,070
Capital Leases 2019	4,334	[1]
Operating Leases 2020	17,605
Capital Leases 2020	4,173	[1]
Operating Leases 2021	17,419
Capital Leases 2021	4,173	[1]
Operating Leases 2022	16,765
Capital Leases 2022	4,173	[1]
Operating Leases Thereafter	1,037,368
Capital Leases Thereafter	67,573	[1]
Operating Lease Total	1,125,098
Capital Leases Total	$ 89,104	[1]

[1] Amounts above represent principal and interest obligations under capital lease arrangements. Related assets with a gross value of $167,324,000 and accumulated depreciation of $29,303,000 are recorded in real property.