Employee Benefit Plans - SERP (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Proceeds from insurance recovery	$ 1,566,000	$ 507,000	$ 2,218,000
Supplemental Retirement Plan ('SERP')
Defined Benefit Plan Disclosure [Line Items]
Variable life insurance policies investment amount	58,000,000.0	55,300,000
Fair value of plan assets	32,039,000	28,476,000
Trading gains (losses), net	2,620,000	(5,524,000)	(2,282,000)
Life insurance, tax free gains	891,000
Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contribution	4,450,000	0
Fair value of plan assets	$ 39,068,000	$ 40,142,000	$ 38,364,000