Goodwill and Franchise Value (Schedule of Franchise Value) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Indefinite-lived Intangible Assets [Roll Forward]
Beginning balance	$ 306,700,000	$ 288,700,000
Adjustments to purchase price allocations		3,500,000
Additions through acquisitions		20,900,000
Reductions through divestitures	(700,000)	(6,000,000.0)
Reductions from impairments	0	(400,000)
Ending balance	$ 306,000,000.0	306,700,000
Franchise value acquired, including purchase accounting adjustments		$ 24,400,000