Other Comprehensive Income (Loss) And Accumulated Other Comprehensive Income (Tables)

12 Months Ended

Dec. 31, 2022

Equity [Abstract]

Schedule of Comprehensive Income (Loss)

The tables below display the changes in Accumulated Other Comprehensive (Loss) Income by component for the years ended December 31, 2022, 2021 and 2020:

(Dollars in Millions)	Net Unrealized Gains (Losses) on Other Investments		Net Unrealized Gains (Losses) on Investments with an Allowance for Credit Losses		Net Unrecognized Postretirement Benefit Costs		(Loss) Gain on Cash Flow Hedges		Total
Balance as of January 1, 2020	$	439.4	$	—	$	(100.6)	$	(2.7)	$	336.1
Other Comprehensive Income (Loss) Before Reclassifications	304.4		(2.1)		4.3		0.4		307.0
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) Net of Tax Benefit (Expense) of $3.6, $—, $(13.5), $— and $(9.9)	(13.2)		—		50.6		—		37.4
Other Comprehensive Income (Loss) Net of Tax (Expense) Benefit of $(78.7), $0.5, $(15.3), $— and $(93.5)	291.2		(2.1)		54.9		0.4		344.4
Balance as of December 31, 2020	$	730.6	$	(2.1)	$	(45.7)	$	(2.3)	$	680.5
Other Comprehensive Loss Before Reclassifications	(182.0)		(1.6)		(6.5)		—		(190.1)
Amounts Reclassified from Accumulated Other Comprehensive Loss Net of Tax Benefit (Expense) of $11.3, $—, $—, $(0.1) and $11.2	(42.8)		—		0.1		0.4		(42.3)
Other Comprehensive (Loss) Income Net of Tax Benefit (Expense) of $59.7, $0.4, $2.4, $(0.1) and $62.4	(224.8)		(1.6)		(6.4)		0.4		(232.4)
Balance as of December 31, 2021	$	505.8	$	(3.7)	$	(52.1)	$	(1.9)	$	448.1
Other Comprehensive (Loss) Income Before Reclassifications	(1,215.1)		2.0		15.2		4.7		(1,193.2)
Amounts Reclassified from Accumulated Other Comprehensive (Loss) Income Net of Tax Benefit (Expense) of $2.7, $0.1, $0.1, $— and $2.9	(10.1)		(0.5)		(0.3)		—		(10.9)
Other Comprehensive (Loss) Income Net of Tax Benefit (Expense) of $325.9, $(0.4), $(4.0), $(1.2) and $320.3	(1,225.2)		1.5		14.9		4.7		(1,204.1)
Balance as of December 31, 2022	$	(719.4)	$	(2.2)	$	(37.2)	$	2.8	$	(756.0)