Indebtedness (Covenants in the Line of Credit) (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Debt Disclosure [Abstract]
Consolidated Net Worth Requirement	$ 1,600,000
Consolidated Net Worth, Actual	$ 2,500,000
Debt-to-capitalization ratio, required	35.00%
Debt-to-capitalization ratio, actual	17.90%