Savings Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 1998	Dec. 31, 1997
Savings Plan [Line Items]
Charges recognized	$ 4,000,000.0	$ 3,900,000	$ 3,700,000
Number of common stock purchased				7,200	46,671
Amount of common stock purchased				$ 200,000	$ 1,000,000.0
Savings Plan
Savings Plan [Line Items]
Employee contribution to savings plan	1
Defined Contribution Plan Employer Employee Contribution	$ 1
Maximum matching contribution	5.00%
Percentage of enrollment of base pay	3.00%
Nonqualified Plan [Member]
Savings Plan [Line Items]
Liability under the restoration plan	$ 1,000,000.0	$ 1,400,000
Liability under the restoration plan, shares	61,394	62,475