Employee Benefits - Obligations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plan
Change in Benefit Obligation:
Benefit obligation at beginning of year	$ 116,000,000	$ 158,000,000
Interest cost	5,000,000	4,000,000	$ 4,000,000
Actuarial gain	2,000,000	(38,000,000)
Annuity payments	(7,000,000)	(7,000,000)
Settlements	(1,000,000)	(1,000,000)
Benefit obligation at end of year	115,000,000	116,000,000	158,000,000
Change in Plan Assets:
Fair value of assets at beginning of year	228,000,000	283,000,000
Actual return (loss) on plan assets	33,000,000	(47,000,000)
Annuity payments	7,000,000	7,000,000
Settlements	(1,000,000)	(1,000,000)
Fair value of assets at end of year	253,000,000	228,000,000	283,000,000
Funded status	138,000,000	112,000,000
Changes recognized in other comprehensive income for the year ended December 31:
Amortization of actuarial gain (loss)	(7,000,000)	(2,000,000)
Amortization of prior service cost		0
Net actuarial (gain) loss arising during the year	(18,000,000)	26,000,000
Total recognized in other comprehensive income for the year (pre-tax)	(25,000,000)	24,000,000
Accumulated other comprehensive loss (pre-tax) not yet recognized in net periodic benefit cost at December 31:
Actuarial (gain) loss, net	(41,000,000)	(66,000,000)
Total accumulated other comprehensive loss (pre-tax)	41,000,000	66,000,000
Post-Retirement Health and Welfare Benefits
Change in Benefit Obligation:
Benefit obligation at beginning of year	7,000,000	10,000,000
Interest cost	1,000,000	0
Actuarial gain	1,000,000	(2,000,000)
Annuity payments	(1,000,000)	(1,000,000)
Benefit obligation at end of year	8,000,000	7,000,000	10,000,000
Change in Plan Assets:
Fair value of assets at beginning of year	0	0
Employer contribution	1,000,000	1,000,000
Annuity payments	1,000,000	1,000,000
Fair value of assets at end of year	0	0	$ 0
Funded status	(8,000,000)	(7,000,000)
Changes recognized in other comprehensive income for the year ended December 31:
Amortization of actuarial gain (loss)		0
Amortization of prior service cost		0
Net actuarial (gain) loss arising during the year	1,000,000	(2,000,000)
Total recognized in other comprehensive income for the year (pre-tax)	1,000,000	(2,000,000)
Accumulated other comprehensive loss (pre-tax) not yet recognized in net periodic benefit cost at December 31:
Prior service cost		0
Actuarial (gain) loss, net	(1,000,000)	(2,000,000)
Total accumulated other comprehensive loss (pre-tax)	$ (1,000,000)	$ (2,000,000)