Derivatives (Tables)

3 Months Ended

Mar. 31, 2025

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivatives Instruments Statements of Financial Performance and Financial Position, Location

The following table presents the Company’s Ultra-Long Treasury Futures derivatives, primary underlying risk exposure, gross notional amount, and estimated fair value of these derivatives:

		March 31, 2025						December 31, 2024
(Dollars in Millions)				Estimated Fair Value						Estimated Fair Value
Derivative Instrument	Primary Underlying Risk Exposure	Gross Notional Amount		Assets		Liabilities		Gross Notional Amount		Assets		Liabilities
Derivatives Designated as Hedging Instruments:
Treasury Futures	Interest Rate Risk	$	75.4	$	—	$	(0.6)	$	75.0	$	—	$	(3.7)

Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss)

The below table reflects the amounts of Gains (Losses) deferred into AOCI before taxes, net changes in amounts in AOCI associated with current hedging transactions, and amounts subsequently reclassified into Net Income through Net Investment Income for Ultra-Long Treasury Futures qualifying as cash flow hedges for the three months ended March 31, 2025 and 2024.

	Three Months Ended
(Dollars in Millions)	Mar 31, 2025		Mar 31, 2024
Beginning of Period	$	(6.3)	$	—
(Losses) Gains Deferred in AOCI	(0.9)		1.5
Net Change in AOCI with Current Period Hedging Transactions	3.0		(1.3)
Losses Reclassified into Income	0.2		—
Net Comprehensive (Losses) Gains from Cash Flow Hedges	$	(4.0)	$	0.2