Retirement Plans and Other Employee Benefits - Schedule of Assumptions Used in the Defined Benefit Plans (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Qualified pension
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan assumptions used calculating benefit obligation, discount rate	2.95%	2.63%	3.31%
Defined benefit plan assumptions used calculating net periodic benefit cost, discount rate	2.64%	3.31%	4.43%
Nonqualified pension
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan assumptions used calculating benefit obligation, discount rate	2.65%	2.24%	3.08%
Defined benefit plan assumptions used calculating net periodic benefit cost, discount rate	2.24%	3.08%	4.26%
Other nonqualified pension
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan assumptions used calculating benefit obligation, discount rate	1.99%	1.41%	2.57%
Defined benefit plan assumptions used calculating net periodic benefit cost, discount rate	1.41%	2.57%	3.83%
Postretirement benefits | Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan assumptions used calculating benefit obligation, discount rate	2.43%	1.92%	2.85%
Defined benefit plan assumptions used calculating net periodic benefit cost, discount rate	1.93%	2.87%	4.04%
Postretirement benefits | Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan assumptions used calculating benefit obligation, discount rate	3.07%	2.81%	3.44%
Defined benefit plan assumptions used calculating net periodic benefit cost, discount rate	2.81%	3.44%	4.56%
Qualified pension/ postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan assumptions used calculating net periodic benefit cost, expected long-term rate of return on plan assets	2.30%	3.45%	4.80%
Postretirement benefit (retirees post January 1, 1993)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan assumptions used calculating net periodic benefit cost, expected long-term rate of return on plan assets	5.80%	6.40%	6.85%
Postretirement benefit (retirees prior to January 1, 1993)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan assumptions used calculating net periodic benefit cost, expected long-term rate of return on plan assets	1.00%	0.90%	0.05%