Employee Benefit Plans - Postretirement Benefit Plans (Details) - USD ($)	3 Months Ended	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in projected benefit obligation:
Actuarial (gains) losses	$ (9,900,000)	$ 6,800,000
Postretirement Plans
Estimated future benefit payments, net of subsidies:
2022	6,000,000.0		$ 6,000,000.0
2023	5,400,000		5,400,000
2024	4,900,000		4,900,000
2025	4,400,000		4,400,000
2026	4,000,000.0		4,000,000.0
Subsequent five years	14,800,000		14,800,000
Change in projected benefit obligation:
Projected benefit obligation — beginning of year			60,500,000	$ 63,600,000
Interest cost			1,000,000.0	1,600,000	$ 2,400,000
Actuarial (gains) losses			(3,900,000)	1,900,000
Benefits paid			(5,900,000)	(6,600,000)
Projected benefit obligation — end of year	51,700,000	60,500,000	51,700,000	60,500,000	63,600,000
Funded status at year-end	(51,700,000)	(60,500,000)	(51,700,000)	(60,500,000)
Other assets	0		0
Accrued expenses	5,900,000	6,700,000	5,900,000	6,700,000
Other long-term liabilities	45,800,000	53,800,000	45,800,000	53,800,000
Net amount recognized	(51,700,000)	(60,500,000)	(51,700,000)	(60,500,000)
Amount recognized in accumulated other comprehensive income (pre-tax) consists of — net prior service (credits) costs	$ (15,500,000)	$ (20,200,000)	(15,500,000)	(20,200,000)
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost			0	0	0
Interest cost			1,000,000.0	1,600,000	2,400,000
Amortization of unrecognized prior service credits			(4,700,000)	(4,700,000)	(4,000,000.0)
Recognized net actuarial (gains) losses			(3,900,000)	1,900,000	2,500,000
Total net periodic pension benefit (income) expense			$ (7,600,000)	$ (1,200,000)	$ 900,000
Assumptions - Actuarial assumptions used in accounting for plans
Health care cost trend rate for next year	6.25%	6.50%	6.25%	6.50%	6.75%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	5.00%	5.00%	5.00%	5.00%	5.00%
Year that the rate reaches the ultimate trend rate			2027	2027	2027
Discount rate used in determining net periodic postretirement benefit expense			2.00%	2.97%	4.09%
Discount rate used in determining year-end postretirement benefit obligation	2.56%	2.00%	2.56%	2.00%	2.97%

Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

Name:	us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.