Pensions - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement (gain)	$ 15	$ 0
Defined Benefit Plan, Type [Extensible List]	Pension Plan
Qualified Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution costs	$ 5,000	3,600
Expected future employer contribution, current fiscal year	25,000
Nonqualified Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution costs	700	$ 500
Expected future employer contribution, current fiscal year	$ 1,400