Pension and Other Postretirement Benefits - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined contribution expense	$ 15,200	$ 13,900	$ 13,500
Accumulated benefit obligation	$ 412,400	269,200
Target asset allocation for the investment of the assets in fixed income securities minimum	55.00%
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	45.00%
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	60.00%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation for the investment of the assets in fixed income securities	40.00%
Target asset allocation for the investment of the assets in equity securities	70.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plans with projected benefit obligation in excess of plan assets, projected benefit obligation	$ 368,500	215,600
Defined benefit pension plans with projected benefit obligation in excess of plan assets, accumulated benefit obligation	362,600	212,700
Defined benefit pension plans with projected benefit obligation in excess of plan assets, fair value of plan assets	257,100	138,500
Settlement loss (gain)	1,342		$ 7,600
Anticipated pension and other postretirement plans contributions, next fiscal year	6,300
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit other postretirement plans with accumulated benefit obligation in excess of plan assets, accumulated benefit obligation	26,100	30,300
Defined benefit other postretirement plans with accumulated benefit obligation in excess of plan assets, fair value of plan assets	0	$ 0
Settlement loss (gain)	0
Anticipated pension and other postretirement plans contributions, next fiscal year	$ 1,400