Leases (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Remaining lease term		3 years
Operating lease cost	$ 258	$ 1,004
Operating lease right-of-use assets	1,580	1,580
Operating lease liabilities	$ 1,580	$ 1,580
Weighted average remaining lease term	1 year 7 months 6 days	1 year 7 months 6 days
Weighted average discount rate	3.10%	3.10%
2020	$ 979	$ 979
2021	540	540
2022	61	61
Property, plant and equipment, gross	567,215	567,215	$ 547,951
Lease income	$ 718	$ 2,951
Maximum
Lessee, Lease, Description [Line Items]
Lessor, renewal term	60 years	60 years
Commercial real estate leased to third parties
Lessee, Lease, Description [Line Items]
Property, plant and equipment, gross	$ 36,378	$ 36,378
Depreciation		$ 10,252