Pension and Other Postretirement Benefits - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined contribution expense	$ 10,000	$ 12,100	$ 11,800
Accumulated benefit obligation	$ 518,400	456,900
Target asset allocation for the investment of the assets in fixed income securities minimum	50.00%
Target asset allocation for the investment of the assets in fixed income securities maximum	90.00%
Target asset allocation for the investment of the assets in equity securities minimum	10.00%
Target asset allocation for the investment of the assets in equity securities maximum	50.00%
Minimum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation for the investment of the assets in fixed income securities	30.00%
Target asset allocation for the investment of the assets in equity securities	50.00%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation for the investment of the assets in fixed income securities	50.00%
Target asset allocation for the investment of the assets in equity securities	70.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plans with projected benefit obligation in excess of plan assets, projected benefit obligation	$ 297,800	293,700
Pension plans with projected benefit obligation in excess of plan assets, accumulated benefit obligation	459,200	400,400
Pension plans with projected benefit obligation in excess of plan assets, fair value of plan assets	463,200	404,900
Settlement loss (gain)	3,153		$ 1,300
Anticipated pension and other postretirement plans contributions, next fiscal year	11,400
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Other postretirement plans with accumulated benefit obligation in excess of plan assets, accumulated benefit obligation	59,200	29,500
Other postretirement plans with accumulated benefit obligation in excess of plan assets, fair value of plan assets	64,000	$ 0
Settlement loss (gain)	0
Anticipated pension and other postretirement plans contributions, next fiscal year	$ 1,500