Employee Benefit Plans - Narrative (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) Retiree shares	Dec. 31, 2019 USD ($) Retiree shares	Dec. 31, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Number of retirees and dependents | Retiree	337	310
Subsidy limit percentage of expected annual fully insured premium over age threshold	60.00%
Subsidy limit percentage of expected annual fully insured premium under age threshold	$ 648,000
Annual subsidy limit percentage increases for fully insured premium over age threshold	3.50%
Estimated contributions next year	$ 2,100,000
Liabilities, including common stock	30,581,000	$ 27,012,000
Compensation (benefit) expense	$ 600,000	2,400,000	$ 3,100,000
Savings Investment Plan
Restructuring Cost and Reserve [Line Items]
Employer matching percent	6.00%
Maximum contribution, percent of employee salary	10.00%
Plan contributions charged to expense	$ 5,600,000	5,800,000	5,900,000
Deferred Compensation Plan
Restructuring Cost and Reserve [Line Items]
Market value of the trust assets, excluding common stock	22,500,000	18,400,000
Liabilities, including common stock	$ 30,600,000	$ 27,000,000.0
Number of common stock deferred into the rabbi trust (in shares) | shares	495,774	495,774
Common stock held in rabbi trust	$ 5,100,000	$ 5,100,000
Contributions to deferred compensation plan	$ 1,000,000.0	$ 1,000,000.0	$ 1,100,000