Revenue Recognition - Disaggregation of Revenue by Major Products and Service Offerings (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Revenue by Major Products/Service Offerings
Total Revenue	$ 17,103	$ 16,331	$ 50,182	$ 47,849
Operating Segments
Revenue by Major Products/Service Offerings
Total Revenue	17,038	16,292	50,017	47,782
Other
Revenue by Major Products/Service Offerings
Revenue	66	38	165	68
Software | Operating Segments
Revenue by Major Products/Service Offerings
Total Revenue	7,804	7,209	22,617	20,932
Software | Hybrid Cloud | Operating Segments
Revenue by Major Products/Service Offerings
Revenue	2,086	1,886	5,988	5,369
Software | Automation | Operating Segments
Revenue by Major Products/Service Offerings
Revenue	1,870	1,934	5,562	5,401
Software | Data | Operating Segments
Revenue by Major Products/Service Offerings
Revenue	1,738	1,459	4,994	4,194
Software | Transaction Processing | Operating Segments
Revenue by Major Products/Service Offerings
Revenue	2,111	1,930	6,073	5,967
Consulting | Operating Segments
Revenue by Major Products/Service Offerings
Total Revenue	5,335	5,324	15,934	15,706
Consulting | Strategy and Technology | Operating Segments
Revenue by Major Products/Service Offerings
Revenue	2,965	2,905	8,794	8,607
Consulting | Intelligent Operations | Operating Segments
Revenue by Major Products/Service Offerings
Revenue	2,370	2,419	7,140	7,100
Infrastructure | Operating Segments
Revenue by Major Products/Service Offerings
Total Revenue	3,707	3,559	10,868	10,586
Infrastructure | Hybrid Infrastructure | Operating Segments
Revenue by Major Products/Service Offerings
Revenue	2,452	2,263	7,130	6,775
Infrastructure | Infrastructure Support | Operating Segments
Revenue by Major Products/Service Offerings
Revenue	1,255	1,296	3,738	3,811
Financing | Operating Segments
Revenue by Major Products/Service Offerings
Total Revenue	$ 192	$ 200	$ 598	$ 557