Restricted Securities Available for Sale (Schedule of Restricted Securities Available for Sale by Aging Category) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Restricted Securities Available For Sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 16.6	$ 37.0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.1	0.4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	12.7	16.9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.2	0.4
Debt Securities, Available-for-sale, Unrealized Loss Position	29.3	53.9
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	0.3	0.8
Corporate Bond Securities [Member]
Restricted Securities Available For Sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4.9	13.1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.1	0.2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	7.5	8.4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.1	0.2
Debt Securities, Available-for-sale, Unrealized Loss Position	12.4	21.5
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	0.2	0.4
US Government and Agency Securities [Member]
Restricted Securities Available For Sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	9.1	19.8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.0	0.2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1.9	4.9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.1	0.2
Debt Securities, Available-for-sale, Unrealized Loss Position	11.0	24.7
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	0.1	0.4
Asset-backed Securities [Member]
Restricted Securities Available For Sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1.6	2.4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3.3	3.6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.0	0.0
Debt Securities, Available-for-sale, Unrealized Loss Position	4.9	6.0
Mortgage-backed Securities [Member]
Restricted Securities Available For Sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1.0	1.7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0.0	0.0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.0	0.0
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 1.0	$ 1.7

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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