Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax liabilities:
Plant, property and equipment	$ 563,289	$ 604,271
Total	563,289	604,271
Deferred income tax assets:
Asset valuations	506,993	720,189
Operating loss carryforwards and credits	95,406	121,658
Pension	96,098	227,681
Foreign tax credit		186,504
Other	469,844	593,140
Total	977,529	1,849,172
Net deferred income tax asset before valuation allowance	414,240	1,244,901
Valuation allowance	95,406	74,552
Net deferred income tax asset	$ 509,646	$ 1,170,349