Retirement Plans - Net Periodic Pension Cost (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 60	$ 56	$ 120	$ 112
Expected return on assets	(46)	(79)	(92)	(158)
Amortization of net loss	24	21	48	42
Net periodic pension cost	$ 38	$ (2)	$ 76	$ (4)