Segment Reporting - Schedule of Current Reportable and Recast of Segments by Revenue (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Revenue
Revenue		$ 2,262	$ 2,332	$ 2,386
Less
Cost of sales		1,386	1,442	1,504
Stock Based Compensation		7	14	30
Depreciation and amortization		111	96	72
Gross Profit		765	794	810
Selling General And Administrative		368	460	408
Restructuring		55	63	73
Stock Based Compensation		12	62	109
Depreciation and intangible amortization		296	299	301
Goodwill impairment	$ 983	3,124	0	0
Interest expense		92	103	131
Other segment item		(104)	(53)	105
Net Income (Loss) From Continuing Operations		(3,078)	(140)	(317)
Technology
Less
Cost of sales		303	313	323
Delivery, Customer Care, and Other
Less
Cost of sales		1,076	1,115	1,151
Recurring
Revenue
Revenue		2,108	2,135	2,167
Project
Revenue
Revenue		154	197	219
Other
Revenue
Revenue		0	0	26
Less
Stock Based Compensation		0	0	0
Depreciation and amortization		0	0	2
Gross Profit		0	0	(2)
Net Income (Loss) From Continuing Operations		0	0	(2)
Other | Technology
Less
Cost of sales		0	0	0
Other | Delivery, Customer Care, and Other
Less
Cost of sales		0	0	26
Other | Recurring
Revenue
Revenue		0	0	26
Other | Project
Revenue
Revenue		0	0	0
Employer Solutions | Employer Solutions
Revenue
Revenue		2,262	2,332	2,360
Less
Stock Based Compensation		7	14	30
Depreciation and amortization		111	96	70
Gross Profit		765	794	812
Selling General And Administrative		368	460	408
Restructuring		55	63	73
Stock Based Compensation		12	62	109
Depreciation and intangible amortization		296	299	301
Goodwill impairment		3,124	0	0
Interest expense		92	103	131
Other segment item		(104)	(53)	105
Net Income (Loss) From Continuing Operations		(3,078)	(140)	(315)
Employer Solutions | Employer Solutions | Technology
Less
Cost of sales		303	313	323
Employer Solutions | Employer Solutions | Delivery, Customer Care, and Other
Less
Cost of sales		1,076	1,115	1,125
Employer Solutions | Employer Solutions | Recurring
Revenue
Revenue		2,108	2,135	2,141
Employer Solutions | Employer Solutions | Project
Revenue
Revenue		$ 154	$ 197	$ 219