Leases (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 411	$ 411
Operating lease payments	746	746
Operating lease right-of-use assets	1,770	1,770
Operating lease liabilities	$ 1,770	$ 1,770
Weighted average remaining lease term	1 year 10 months 24 days	1 year 10 months 24 days
Weighted average discount rate	3.10%	3.10%
2019	$ 236	$ 236
2020	934	934
2021	540	540
2022	60	$ 60
Lessor, Operating Lease, Existence of Option to Extend [true false]		true
Property, plant and equipment, gross	561,666	$ 561,666	$ 547,951	$ 543,177
Lease income	733	$ 2,232
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term		3 years
Commercial real estate leased to third parties
Lessee, Lease, Description [Line Items]
Property, plant and equipment, gross	$ 36,362	$ 36,362
Depreciation		$ 10,071
Commercial real estate leased to third parties | Maximum
Lessee, Lease, Description [Line Items]
Lessor, renewal term	60 years	60 years