Annual report pursuant to Section 13 and 15(d)

Retirement Savings Plans (Narrative) (Details)

v3.20.4
Retirement Savings Plans (Narrative) (Details) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Liability to participants under deferred compensation plan $ 18,700,000 $ 14,000,000.0  
Current liability to participants under deferred compensation plan 1,200,000 1,700,000  
401(k) Profit-Sharing Plan [Member]      
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Company contributions to the plan 10,100,000 9,400,000 $ 8,900,000
Deferred Compensation Plan [Member]      
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Company contributions to the plan 400,000 500,000 $ 400,000
Other Noncurrent Assets [Member] | Deferred Compensation Plan [Member]      
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Fair value of mutual fund investments 18,700,000 14,000,000.0  
Short-term Investments [Member] | Deferred Compensation Plan [Member]      
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Fair value of mutual fund investments $ 1,200,000 $ 1,700,000