Pensions - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement loss	$ 986	$ 719	$ 1,010	$ 719
Remeasurement loss	$ 29,461	13,616	$ 30,200	13,616
Defined Benefit Plan, Type [Extensible List]	us-gaap:PensionPlansDefinedBenefitMember		us-gaap:PensionPlansDefinedBenefitMember
Qualified Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution costs	$ 9,900	22,100	$ 25,700	25,700
Expected future employer contribution, current fiscal year	30,900		30,900
Nonqualified Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution costs	200	$ 300	800	$ 600
Expected future employer contribution, current fiscal year	$ 1,400		$ 1,400