Retirement Plans and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Thousands		6 Months Ended
	Jul. 24, 2017	Jun. 30, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Employee hire date no longer eligible for noncontributory retirement plan		Dec. 08, 2009
Other Post Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions for next fiscal year			$ 121
Defined benefit plan, contributions by employer		$ 58
Defined benefit plan, benefits paid		58
Nonqualified Plan [Member] | Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions for next fiscal year			$ 160
Defined benefit plan, contributions by employer		80
Defined benefit plan, benefits paid		$ 1,300
Subsequent Event [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, contributions by employer	$ 2,000