Federal and State Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Accrued expenses not deductible until paid	$ 7,017	$ 6,062
Goodwill and intangible assets	1,353	0
Net operating loss carry forwards	286	178
Allowance for doubtful accounts	245	496
Equity incentive plan	207	246
Other	118	110
Revenue recognition	11	124
Total deferred tax assets	9,237	7,216
Deferred tax liabilities:
Tax over book depreciation	(31,009)	(26,806)
Prepaid expenses deductible when paid	(1,654)	(1,514)
Capital leases	(92)	(32)
Total deferred tax liabilities	(32,755)	(28,352)
Net deferred tax liabilities	$ (23,518)	$ (21,136)