Employee Benefit Plans - Profit Sharing and Savings Plans (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Other Comprehensive Income (Loss), Tax	$ 15,600,000	$ 15,600,000	$ 12,400,000	$ (3,300,000)
Eligibility requirement, service hours to be completed		20 hours
Deferred Profit Sharing
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Eligibility requirement, requisite service period		2 years
Compensation expense			2,100,000	2,400,000
Savings Plan, Employee Elected
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Compensation expense		$ 8,900,000	$ 7,000,000.0	$ 6,300,000
Maximum annual contribution per employee, amount per dollar of employee contribution		$ 1
Maximum annual contribution per employee, percent		5.00%