v3.26.1
Financial Risks - Summary of Non-derivative Financial Liabilities and Derivative Financial Liabilities by a Remaining Contract Maturity Period (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Within 1 year [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Total ¥ (18,991,630) ¥ (17,028,902)
Between 1 and 3 years [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Total (17,447,584) (15,833,244)
Between 3 and 5 years [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Total (7,641,092) (6,314,963)
Later than 5 years [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Total (2,548,667) (2,694,201)
Book value [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Total 43,563,423 39,112,760
Contractual cash flows [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Total (46,628,974) (41,871,310)
Derivative financial liabilities [Member] | Within 1 year [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Interest derivatives (138,388) (83,505)
In 240,393 73,959
Out (323,462) (130,116)
Total (221,457) (139,663)
Derivative financial liabilities [Member] | Between 1 and 3 years [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Interest derivatives (148,377) (108,063)
In 391,484 759,648
Out (414,493) (840,065)
Total (171,386) (188,480)
Derivative financial liabilities [Member] | Between 3 and 5 years [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Interest derivatives (40,179) (22,712)
In 43,039 66,990
Out (47,022) (74,389)
Total (44,163) (30,111)
Derivative financial liabilities [Member] | Later than 5 years [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Interest derivatives (12,348) (6,061)
In 161,134 146,931
Out (164,627) (152,181)
Total (15,842) (11,311)
Derivative financial liabilities [Member] | Book value [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Interest derivatives 255,068 196,389
Out 102,887 123,493
Total 357,955 319,881
Derivative financial liabilities [Member] | Contractual cash flows [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Interest derivatives (339,292) (220,341)
In 836,049 1,047,528
Out (949,605) (1,196,751)
Total (452,848) (369,564)
Non-derivative financial liabilities [Member] | Within 1 year [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Short-term debt (1,353,907) (1,565,387)
Commercial paper (4,453,267) (4,012,371)
Long-term debt (12,768,209) (11,209,068)
Lease liabilities (194,791) (102,412)
Total (18,770,173) (16,889,239)
Non-derivative financial liabilities [Member] | Between 1 and 3 years [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Long-term debt (17,094,270) (15,485,265)
Lease liabilities (181,928) (159,500)
Total (17,276,198) (15,644,764)
Non-derivative financial liabilities [Member] | Between 3 and 5 years [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Long-term debt (7,489,266) (6,190,498)
Lease liabilities (107,664) (94,354)
Total (7,596,929) (6,284,852)
Non-derivative financial liabilities [Member] | Later than 5 years [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Long-term debt (2,171,143) (2,409,143)
Lease liabilities (361,683) (273,747)
Total (2,532,826) (2,682,891)
Non-derivative financial liabilities [Member] | Book value [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Short-term debt 1,339,878 1,552,166
Commercial paper 4,359,205 3,912,303
Long-term debt 36,795,373 32,795,058
Lease liabilities 711,013 533,351
Total 43,205,469 38,792,879
Non-derivative financial liabilities [Member] | Contractual cash flows [Member]    
Disclosure of non-derivative financial liabilities and derivative financial liabilities by a remaining contract maturity period [Line items]    
Short-term debt (1,353,907) (1,565,387)
Commercial paper (4,453,267) (4,012,371)
Long-term debt (39,522,887) (35,293,975)
Lease liabilities (846,065) (630,013)
Total ¥ (46,176,126) ¥ (41,501,746)