Long-Term Debt (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility commitment fee amount, percentage	0.15%
Covenant ratio debt EBITDA maximum numerator	3.25
Covenant ratio coverage maximum numerator	4.00
Line of Credit | LIBOR
Line of Credit Facility [Line Items]
Credit facility interest rate, percentage	1.00%
Margin for LIBOR based loans, percentage	1.13%
Line of Credit | Federal Funds
Line of Credit Facility [Line Items]
Credit facility interest rate, percentage	0.50%
Line of Credit | Base Rate
Line of Credit Facility [Line Items]
Margin for base rate loans, percentage	0.13%
Letter of credit
Line of Credit Facility [Line Items]
Letters of credit from a variety of banks	$ 11.6
Letters of Credit Term	1 year