Segment Information and Concentrations - Net Income Reconciled to Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Pension mark-to-market	$ 19	$ 0	$ 19	$ 0
Corporate and other income and expenses not allocated to reportable segments	125	112	341	307
Eliminations	9	11	26	25
Transformation and restructuring costs	8	17	7	93
Amortization expense	43	44	128	130
Acquisition-related costs	0	1	1	9
Loss (gains) on derivatives recognized during the period	(85)	0	(85)	0
Interest expense	85	74	259	204
Interest income	(5)	(3)	(11)	(6)
Depreciation and amortization (excluding acquisition-related amortization of intangibles)	109	107	324	314
Income tax expense (benefit)	236	43	280	56
Stock-based compensation expense	30	28	98	97
Separation costs	76	0	147	0
Cyber ransomware incident recovery costs	12	0	23	0
Russia	0	0	0	22
Income (loss) from continuing operations	(124)	69	(95)	71
Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA by segment	538	$ 503	$ 1,462	$ 1,322
Cost of services
Segment Reporting Information [Line Items]
Loss (gains) on derivatives recognized during the period	(85)
Interest expense
Segment Reporting Information [Line Items]
Loss (gains) on derivatives recognized during the period	$ (18)