v3.26.3
Segment Information (Disaggregation of Revenues for Revenues From Contracts With Customers, by Goods and Services Category and Geographical Location) (Detail) - JPY (¥)
¥ in Millions
 6 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Segment Reporting Information [Line Items]    
Revenues from contracts with customers ¥ 800,205 ¥ 704,351
Other revenues [1] 873,670 823,248
Segment revenues/Total revenues 1,673,875 1,527,599
Sales of goods    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 174,725 144,154
Real estate sales    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 58,543 62,810
Asset Management and Servicing    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 178,150 133,261
Automobile related services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 46,423 44,612
Facilities operation    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 53,103 51,678
Environment and energy services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 68,688 88,818
Real estate management and brokerage    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 53,202 53,191
Real estate contract work    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 78,937 75,237
Other    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 88,434 50,590
Operating Segment    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 795,094 699,527
Other revenues [1] 877,674 827,999
Segment revenues/Total revenues 1,672,768 1,527,526
Operating Segment | Sales of goods    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 172,728 142,027
Operating Segment | Real estate sales    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 58,543 62,810
Operating Segment | Asset Management and Servicing    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 178,374 133,422
Operating Segment | Automobile related services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 46,423 44,690
Operating Segment | Facilities operation    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 53,171 51,891
Operating Segment | Environment and energy services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 69,712 89,468
Operating Segment | Real estate management and brokerage    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 53,738 53,841
Operating Segment | Real estate contract work    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 79,451 76,064
Operating Segment | Other    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 82,954 45,314
Operating Segment | Japan & APAC    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 291,587 239,867
Other revenues [1] 319,106 315,681
Segment revenues/Total revenues 610,693 555,548
Operating Segment | Japan & APAC | Sales of goods    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 161,602 137,210
Operating Segment | Japan & APAC | Real estate sales    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | Japan & APAC | Asset Management and Servicing    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 352
Operating Segment | Japan & APAC | Automobile related services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 46,370 44,597
Operating Segment | Japan & APAC | Facilities operation    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 2,926 790
Operating Segment | Japan & APAC | Environment and energy services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 1,654 1,826
Operating Segment | Japan & APAC | Real estate management and brokerage    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | Japan & APAC | Real estate contract work    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 29,455 27,049
Operating Segment | Japan & APAC | Other    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 49,580 28,043
Operating Segment | Infrastructure    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 305,663 324,026
Other revenues [1] 96,216 128,663
Segment revenues/Total revenues 401,879 452,689
Operating Segment | Infrastructure | Sales of goods    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 9,498 4,242
Operating Segment | Infrastructure | Real estate sales    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 58,543 62,810
Operating Segment | Infrastructure | Asset Management and Servicing    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 4,703 3,899
Operating Segment | Infrastructure | Automobile related services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 53 93
Operating Segment | Infrastructure | Facilities operation    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 50,245 51,101
Operating Segment | Infrastructure | Environment and energy services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 68,058 87,642
Operating Segment | Infrastructure | Real estate management and brokerage    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 53,738 53,841
Operating Segment | Infrastructure | Real estate contract work    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 49,996 49,015
Operating Segment | Infrastructure | Other    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 10,829 11,383
Operating Segment | USA & Europe    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 197,844 135,634
Other revenues [1] 148,685 82,636
Segment revenues/Total revenues 346,529 218,270
Operating Segment | USA & Europe | Sales of goods    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 1,628 575
Operating Segment | USA & Europe | Real estate sales    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | USA & Europe | Asset Management and Servicing    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 173,671 129,171
Operating Segment | USA & Europe | Automobile related services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | USA & Europe | Facilities operation    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | USA & Europe | Environment and energy services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | USA & Europe | Real estate management and brokerage    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | USA & Europe | Real estate contract work    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | USA & Europe | Other    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 22,545 5,888
Operating Segment | Insurance    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Other revenues [1] 313,667 301,019
Segment revenues/Total revenues 313,667 301,019
Operating Segment | Insurance | Sales of goods    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | Insurance | Real estate sales    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | Insurance | Asset Management and Servicing    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | Insurance | Automobile related services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | Insurance | Facilities operation    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | Insurance | Environment and energy services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | Insurance | Real estate management and brokerage    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | Insurance | Real estate contract work    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Operating Segment | Insurance | Other    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Corporate revenue and intersegment transactions    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 5,111 4,824
Other revenues [1] (4,004) (4,751)
Segment revenues/Total revenues 1,107 73
Corporate revenue and intersegment transactions | Sales of goods    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 1,997 2,127
Corporate revenue and intersegment transactions | Real estate sales    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 0
Corporate revenue and intersegment transactions | Asset Management and Servicing    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers (224) (161)
Corporate revenue and intersegment transactions | Automobile related services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers 0 (78)
Corporate revenue and intersegment transactions | Facilities operation    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers (68) (213)
Corporate revenue and intersegment transactions | Environment and energy services    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers (1,024) (650)
Corporate revenue and intersegment transactions | Real estate management and brokerage    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers (536) (650)
Corporate revenue and intersegment transactions | Real estate contract work    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers (514) (827)
Corporate revenue and intersegment transactions | Other    
Segment Reporting Information [Line Items]    
Revenues from contracts with customers ¥ 5,480 ¥ 5,276
[1] Other revenues include revenues that are not in the scope of revenue from contracts with customers, such as life insurance premiums and related investment income, operating leases, finance revenues that include interest income, and others.