Comprehensive Income and Accumulated Other Comprehensive Income (Loss) - Summary of Effects of Reclassifications from Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Settlement gain
Amortization of pension and other postretirement benefit plan items:
Total before tax	$ (7)
Pension and Other Postretirement Benefit Plans
Amortization of pension and other postretirement benefit plan items:
Total net of tax	(1,113)	$ (3,123)
Amount Reclassified from Accumulated Other Comprehensive Income | Actuarial losses
Amortization of pension and other postretirement benefit plan items:
Total before tax	1,299
Amount Reclassified from Accumulated Other Comprehensive Income | Prior service cost
Amortization of pension and other postretirement benefit plan items:
Total before tax	169
Amount Reclassified from Accumulated Other Comprehensive Income | Pension and Other Postretirement Benefit Plans
Amortization of pension and other postretirement benefit plan items:
Total before tax	1,461
Tax benefit	(348)
Total net of tax	$ 1,113