Pensions - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement (gain)/loss	$ 0	$ (986)	$ 15	$ (1,010)
Qualified Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution costs	5,000	9,900	20,000	25,700
Expected future employer contribution, current fiscal year	25,000		25,000
Nonqualified Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution costs	200	$ 200	1,000	$ 800
Expected future employer contribution, current fiscal year	$ 1,400		$ 1,400