Segment Reporting (Schedule of Segment Reporting Information, Reconcile to Net Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting [Abstract]
Revenues	$ 419.1	$ 390.6	$ 1,231.3	$ 1,162.0
Labor and Related Expense	60.7	53.1	183.9	166.9
Share-based Payment Arrangement, Noncash Expense	18.4	15.8	51.8	45.2
Equipment Expense	12.5	11.6	37.0	33.6
Registry fee expenses	12.1	11.3	35.4	33.9
Depreciation of property and equipment	7.3	9.0	24.5	28.1
Segment Reporting, Other Segment Item, Amount	23.8	20.5	62.5	59.9
Operating Expenses	134.8	121.3	395.1	367.6
Operating income	284.3	269.3	836.2	794.4
Interest Expense	18.9	18.9	58.1	56.5
Nonoperating Gains (Losses)	6.3	10.5	19.3	35.9
Income tax expense from continuing operations	58.9	59.6	177.9	179.6
Net Income	$ 212.8	$ 201.3	$ 619.5	$ 594.2