Employee Benefit Plans - Narrative (Details) $ / shares in Units, shares in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) executive $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accrued matching contribution	$ 1,700,000	$ 1,400,000
Employee stock purchase plan (in shares) | shares	19	17	19
Average purchase price (in dollars per share) | $ / shares	$ 29.43	$ 32.79	$ 28.93
Current deferred compensation liability	$ 4,200,000	$ 3,600,000
Deferred compensation plan	34,501,000	30,361,000
Compensation expenses	1,000,000.0	400,000	$ 800,000
Proceeds from sale of life insurance policy	3,500,000
Deferred compensation plan assets	36,164,000	35,413,000
Net death benefit of life insurance	$ 169,600,000
Number of executives in SERP | executive	2
Normal retirement age	65 years
Early retirement age	55 years
Benefits payable targeted percentage	45.00%
Period in which the executive officer earned the highest salary and bonus	3 years
Employment period for computation of benefit	10 years
Eligible age under condition one for reduced benefits under the plan	62 years
Eligible service under condition one for reduced benefits under plan	10 years
Eligible age under condition two for reduced benefits under plan	55 years
Eligible service under condition two for reduced benefits under plan	25 years
Lump sum payment period	10 years
Payment to participants under the SERP	$ 0	0
Accumulated benefit obligation	20,628,000	18,080,000	$ 15,035,000
Employer contributions to benefit plans	0
Expected future benefit payments, next twelve months	0
Accumulated benefit obligation	$ 20,600,000	$ 18,100,000
ESPP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of discount on shares purchased under employee stock purchase plan	5.00%