v3.26.3
Debt (Detail)
€ in Millions, ¥ in Millions, SFr in Millions, $ in Millions, $ in Millions
Sep. 30, 2026
USD ($)
Sep. 30, 2026
EUR (€)
Aug. 24, 2026
USD ($)
Aug. 24, 2026
CHF (SFr)
Jun. 10, 2026
USD ($)
Jun. 10, 2026
CAD ($)
May 20, 2026
USD ($)
May 14, 2026
USD ($)
May 14, 2026
CNY (¥)
Mar. 17, 2026
USD ($)
Mar. 17, 2026
CHF (SFr)
INA Senior Notes Due May 2026 | Senior Notes [Member]                      
Debt Instrument [Line Items]                      
Debt Instrument, Face Amount $ 1,500                    
Debt Instrument, Interest Rate, Stated Percentage 3.35% 3.35%                  
INA EUR Senior Notes Due June 2027 [Member] | Senior Notes [Member]                      
Debt Instrument [Line Items]                      
Debt Instrument, Face Amount | €   € 575                  
Debt Instrument, Interest Rate, Stated Percentage 0.875% 0.875%                  
Senior Notes [Member] | INA CHF Bond Due 2032                      
Debt Instrument [Line Items]                      
Debt Instrument, Face Amount                   $ 254 SFr 200
Debt Instrument, Interest Rate, Stated Percentage                   1.02% 1.02%
Senior Notes [Member] | INA CNH Bond Due May 2031 [Member]                      
Debt Instrument [Line Items]                      
Debt Instrument, Face Amount               $ 367 ¥ 2,500    
Debt Instrument, Interest Rate, Stated Percentage               2.40% 2.40%    
Senior Notes [Member] | INA CNH Bonds Due 2036                      
Debt Instrument [Line Items]                      
Debt Instrument, Face Amount               $ 220 ¥ 1,500    
Debt Instrument, Interest Rate, Stated Percentage               2.85% 2.85%    
Senior Notes [Member] | INA Senior Notes Due May 2036                      
Debt Instrument [Line Items]                      
Debt Instrument, Face Amount             $ 1,000        
Debt Instrument, Interest Rate, Stated Percentage             5.30%        
Senior Notes [Member] | INA CAD Senior Notes Due June 2031                      
Debt Instrument [Line Items]                      
Debt Instrument, Face Amount         $ 286 $ 400          
Debt Instrument, Interest Rate, Stated Percentage         3.78% 3.78%          
Senior Notes [Member] | INA CAD Senior Notes Due June 2033                      
Debt Instrument [Line Items]                      
Debt Instrument, Face Amount         $ 286 $ 400          
Debt Instrument, Interest Rate, Stated Percentage         4.034% 4.034%          
Senior Notes [Member] | INA CHF Senior Notes Due August 2029                      
Debt Instrument [Line Items]                      
Debt Instrument, Face Amount     $ 216 SFr 175              
Debt Instrument, Interest Rate, Stated Percentage     0.86% 0.86%              
Senior Notes [Member] | INA CHF Senior Notes Due August 2033                      
Debt Instrument [Line Items]                      
Debt Instrument, Face Amount     $ 278 SFr 225              
Debt Instrument, Interest Rate, Stated Percentage     1.22% 1.22%