Employee Benefit Plans - Weighted Assumptions (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SERPs
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average discount rate	3.12%	4.15%	3.50%
Discount rate	2.33%	3.12%
Restoration Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average discount rate	3.12%	4.23%	3.57%
Discount rate	2.36%	3.12%