Background and Summary of Significant Accounting Policies - Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) reporting_unit segment	Dec. 31, 2023 USD ($)
Statement [Line Items]
Bank overdrafts	$ 1	$ 0
Accounts receivable, period past due	30 days
Number of reporting units | reporting_unit	1
Number of operating segments | segment	1
Capitalized software
Statement [Line Items]
Finite-lived intangible assets, maximum useful life	7 years
Affiliated Entity | Pension, Supplemental and Other Postretirement Benefit Plans
Statement [Line Items]
Pension settlement term	30 years
Revenue from affiliate	$ 52	57
Affiliated Entity | Pension, Supplemental and Other Postretirement Benefit Plans
Statement [Line Items]
Revenue from affiliate	$ 52	$ 57
Minimum
Statement [Line Items]
Contract term	1 year
Maximum
Statement [Line Items]
Contract term	5 years
Customer relationship period for revenue recognition	20 years
Average | Consumer customers, average contract life
Statement [Line Items]
Customer life	50 months
Average | Business customer, average contract life
Statement [Line Items]
Customer life	35 months