v3.26.1
Parent Company Only Condensed Financial Information - Condensed Balance Sheets (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Assets [Abstract]      
Cash and cash equivalents ¥ 4,298,693 ¥ 4,424,462 ¥ 4,239,359
Receivables from other than customers 1,345,631 1,030,023  
Securities purchased under agreements to resell 13,210,236 14,004,757  
Trading assets 26,128,073 22,372,339  
Private equity and debt investments 214,014 151,710  
Investments in subsidiaries and affiliates 535,402 506,389  
Investments in equity securities 123,191 98,401  
Other assets 1,598,457 1,124,473  
Total assets 62,645,925 56,802,170  
Liabilities [Abstract]      
Payables to other than customers 3,432,040 2,766,112  
Securities loaned 2,448,284 1,964,682  
Other liabilities 1,813,635 1,456,598  
Long-term borrowings 15,544,956 13,373,678  
Total liabilities 58,791,010 53,221,171  
Equity, Attributable to Parent [Abstract]      
Common stock 594,493 594,493  
Additional paid-in capital 706,261 704,877  
Retained earnings 2,013,986 1,867,379  
Accumulated other comprehensive income (loss) 548,221 447,808  
Common stock held in treasury, at cost 155,093 143,678  
Total equity 3,707,868 3,470,879  
Total liabilities and equity 62,645,925 56,802,170  
Parent Company [Member]      
Assets [Abstract]      
Cash and cash equivalents 181,147 149,626  
Loans receivable to subsidiaries 8,425,447 7,575,326  
Receivables from other than customers 175,106 214,520  
Dividends receivable from subsidiaries and affiliates 254,764 190,104  
Securities purchased under agreements to resell 135,664 212,836  
Trading assets 28,457 18,876  
Private equity and debt investments 31,283 30,704  
Investments in subsidiaries and affiliates 3,492,266 3,172,744  
Investments in equity securities 122,744 97,954  
Other assets 314,707 294,532  
Total assets 13,161,585 11,957,222  
Liabilities [Abstract]      
Short-term borrowings from subsidiaries 3,358,500 2,835,900  
Payables to other than customers 2,122 2,441  
Securities loaned 73,049 87,275  
Other liabilities 374,949 431,978  
Long-term borrowings 3,882,293 3,468,874  
Long-term borrowings from subsidiaries 1,762,804 1,659,875  
Total liabilities 9,453,717 8,486,343  
Equity, Attributable to Parent [Abstract]      
Common stock 594,493 594,493  
Additional paid-in capital 706,261 704,877  
Retained earnings 2,013,986 1,867,379  
Accumulated other comprehensive income (loss) 548,221 447,808  
Total NHI shareholders' equity before treasury stock 3,862,961 3,614,557  
Common stock held in treasury, at cost (155,093) (143,678)  
Total equity 3,707,868 3,470,879  
Total liabilities and equity ¥ 13,161,585 ¥ 11,957,222