Summary of Significant Accounting Policies (Schedule of Effects of Change in Accounting Estimate) (Details) - Change in accounting method accounted for as change in estimate [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Change in Accounting Estimate [Line Items]
Change in Accounting Estimate, Description	During first quarter 2020, we changed the estimated life of certain trucks expected to be sold in 2020 to more rapidly depreciate the trucks to their estimated residual values due to the weak used truck market.
Depreciation		$ 9.6