Retirement Plans and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Thousands		9 Months Ended
	Jul. 05, 2018	Sep. 30, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Employee hire date no longer eligible for noncontributory retirement plan		Dec. 08, 2009
Defined benefit plan, contributions by employer	$ 3,000
Other Post Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions for next fiscal year			$ 80
Defined benefit plan, contributions by employer		$ 79
Defined benefit plan, benefits paid		79
Nonqualified Plan [Member] | Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions for next fiscal year			$ 158
Defined benefit plan, contributions by employer		120
Defined benefit plan, benefits paid		$ 2,000