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Bonds Payable - Major Terms of Domestic Unsecured Bonds (Detail)
$ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2024
TWD ($)
Dec. 31, 2024
USD ($)
Domestic Unsecured Bonds Hundred And One Four [member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2013-01  
Issuance ending period 2023-01  
Coupon Rate 1.49% 1.49%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And One Four [member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 3,000.0  
Domestic Unsecured Bonds Hundred And Two One [member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2013-02  
Issuance ending period 2023-02  
Coupon Rate 1.50% 1.50%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Two One [member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 3,600.0  
Domestic Unsecured Bonds Hundred And Two Two [member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2013-07  
Issuance ending period 2023-07  
Coupon Rate 1.70% 1.70%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Two Two [member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 3,500.0  
Domestic Unsecured Bonds Hundred And Two Four [member] | Tranche E [member]    
Bonds payable [line items]    
Issuance starting period 2013-09  
Issuance ending period 2023-03  
Coupon Rate 2.05% 2.05%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Two Four [member] | Tranche F [member]    
Bonds payable [line items]    
Issuance starting period 2013-09  
Issuance ending period 2023-09  
Coupon Rate 2.10% 2.10%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Two Four [member] | Taiwan [member] | Tranche E [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 5,400.0  
Domestic Unsecured Bonds Hundred And Two Four [member] | Taiwan [member] | Tranche F [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 2,600.0  
Domestic Unsecured Bonds Hundred And Nine One [Member]    
Bonds payable [line items]    
Issuance starting period 2020-09  
Issuance ending period 2060-09  
Coupon Rate 2.70% 2.70%
Repayment and Interest Payment Bullet repayment (callable onthe 5th anniversary of theissue date and everyanniversary thereafter);interest payable annually  
Domestic Unsecured Bonds Hundred And Nine One [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2020-03  
Issuance ending period 2025-03  
Coupon Rate 0.58% 0.58%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine One [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2020-03  
Issuance ending period 2027-03  
Coupon Rate 0.62% 0.62%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine One [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2020-03  
Issuance ending period 2030-03  
Coupon Rate 0.64% 0.64%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine One [Member] | Taiwan [member]    
Bonds payable [line items]    
Domestic unsecured bonds   $ 1,000.0
Domestic Unsecured Bonds Hundred And Nine One [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 3,000.0  
Domestic Unsecured Bonds Hundred And Nine One [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 10,500.0  
Domestic Unsecured Bonds Hundred And Nine One [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 10,500.0  
Domestic Unsecured Bonds Hundred And Nine Two [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2020-04  
Issuance ending period 2025-04  
Coupon Rate 0.52% 0.52%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Two [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2020-04  
Issuance ending period 2027-04  
Coupon Rate 0.58% 0.58%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Two [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2020-04  
Issuance ending period 2030-04  
Coupon Rate 0.60% 0.60%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Two [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 5,900.0  
Domestic Unsecured Bonds Hundred And Nine Two [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 10,400.0  
Domestic Unsecured Bonds Hundred And Nine Two [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 5,300.0  
Domestic Unsecured Bonds Hundred And Nine Three [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2020-05  
Issuance ending period 2025-05  
Coupon Rate 0.55% 0.55%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Three [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2020-05  
Issuance ending period 2027-05  
Coupon Rate 0.60% 0.60%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Three [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2020-05  
Issuance ending period 2030-05  
Coupon Rate 0.64% 0.64%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Three [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,500.0  
Domestic Unsecured Bonds Hundred And Nine Three [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 7,500.0  
Domestic Unsecured Bonds Hundred And Nine Three [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 2,400.0  
Domestic Unsecured Bonds Hundred And Nine Four [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2020-07  
Issuance ending period 2025-07  
Coupon Rate 0.58% 0.58%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Four [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2020-07  
Issuance ending period 2027-07  
Coupon Rate 0.65% 0.65%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Four [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2020-07  
Issuance ending period 2030-07  
Coupon Rate 0.67% 0.67%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Four [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 5,700.0  
Domestic Unsecured Bonds Hundred And Nine Four [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 6,300.0  
Domestic Unsecured Bonds Hundred And Nine Four [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 1,900.0  
Domestic Unsecured Bonds Hundred And Nine Five [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2020-09  
Issuance ending period 2025-09  
Coupon Rate 0.50% 0.50%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Five [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2020-09  
Issuance ending period 2027-09  
Coupon Rate 0.58% 0.58%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Five [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2020-09  
Issuance ending period 2030-09  
Coupon Rate 0.60% 0.60%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Five [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,800.0  
Domestic Unsecured Bonds Hundred And Nine Five [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 8,000.0  
Domestic Unsecured Bonds Hundred And Nine Five [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 2,800.0  
Domestic Unsecured Bonds Hundred And Nine Six Green Bond [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2020-12  
Issuance ending period 2025-12  
Coupon Rate 0.40% 0.40%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Six Green Bond [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2020-12  
Issuance ending period 2027-12  
Coupon Rate 0.44% 0.44%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Six Green Bond [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2020-12  
Issuance ending period 2030-12  
Coupon Rate 0.48% 0.48%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Six Green Bond [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 1,600.0  
Domestic Unsecured Bonds Hundred And Nine Six Green Bond [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 5,600.0  
Domestic Unsecured Bonds Hundred And Nine Six Green Bond [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,800.0  
Domestic Unsecured Bonds Hundred And Nine Seven [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2020-12  
Issuance ending period 2025-12  
Coupon Rate 0.36% 0.36%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Seven [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2020-12  
Issuance ending period 2027-12  
Coupon Rate 0.41% 0.41%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Seven [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2020-12  
Issuance ending period 2030-12  
Coupon Rate 0.45% 0.45%
Repayment and Interest Payment Two equal installments in last two years; interest payable annually  
Domestic Unsecured Bonds Hundred And Nine Seven [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 1,900.0  
Domestic Unsecured Bonds Hundred And Nine Seven [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 10,200.0  
Domestic Unsecured Bonds Hundred And Nine Seven [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 6,400.0  
Domestic Unsecured Bonds Hundred And Ten One [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2021-03  
Issuance ending period 2026-03  
Coupon Rate 0.50% 0.50%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten One [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2021-03  
Issuance ending period 2028-03  
Coupon Rate 0.55% 0.55%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten One [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2021-03  
Issuance ending period 2031-03  
Coupon Rate 0.60% 0.60%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten One [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,800.0  
Domestic Unsecured Bonds Hundred And Ten One [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 11,400.0  
Domestic Unsecured Bonds Hundred And Ten One [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,900.0  
Domestic Unsecured Bonds Hundred And Ten Two [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2021-05  
Issuance ending period 2026-05  
Coupon Rate 0.50% 0.50%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Two [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2021-05  
Issuance ending period 2028-05  
Coupon Rate 0.58% 0.58%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Two [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2021-05  
Issuance ending period 2031-05  
Coupon Rate 0.65% 0.65%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Two [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 5,200.0  
Domestic Unsecured Bonds Hundred And Ten Two [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 8,400.0  
Domestic Unsecured Bonds Hundred And Ten Two [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 5,600.0  
Domestic Unsecured Bonds Hundred And Ten Three [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2021-06  
Issuance ending period 2026-06  
Coupon Rate 0.52% 0.52%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Three [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2021-06  
Issuance ending period 2028-06  
Coupon Rate 0.58% 0.58%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Three [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2021-06  
Issuance ending period 2031-06  
Coupon Rate 0.65% 0.65%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Three [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 6,900.0  
Domestic Unsecured Bonds Hundred And Ten Three [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 7,900.0  
Domestic Unsecured Bonds Hundred And Ten Three [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,900.0  
Domestic Unsecured Bonds Hundred And Ten Four [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2021-08  
Issuance ending period 2025-08  
Coupon Rate 0.485% 0.485%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Four [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2021-08  
Issuance ending period 2026-08  
Coupon Rate 0.50% 0.50%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Four [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2021-08  
Issuance ending period 2028-08  
Coupon Rate 0.55% 0.55%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Four [Member] | Tranche D [member]    
Bonds payable [line items]    
Issuance starting period 2021-08  
Issuance ending period 2031-08  
Coupon Rate 0.62% 0.62%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Four [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,000.0  
Domestic Unsecured Bonds Hundred And Ten Four [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 8,000.0  
Domestic Unsecured Bonds Hundred And Ten Four [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds 5,400.0  
Domestic Unsecured Bonds Hundred And Ten Four [Member] | Taiwan [member] | Tranche D [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,200.0  
Domestic Unsecured Bonds Hundred And Ten Six [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2021-10  
Issuance ending period 2026-04  
Coupon Rate 0.535% 0.535%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Six [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2021-10  
Issuance ending period 2026-10  
Coupon Rate 0.54% 0.54%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Six [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2021-10  
Issuance ending period 2028-10  
Coupon Rate 0.60% 0.60%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Six [Member] | Tranche D [member]    
Bonds payable [line items]    
Issuance starting period 2021-10  
Issuance ending period 2031-10  
Coupon Rate 0.62% 0.62%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Six [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 3,200.0  
Domestic Unsecured Bonds Hundred And Ten Six [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 6,900.0  
Domestic Unsecured Bonds Hundred And Ten Six [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds 4,600.0  
Domestic Unsecured Bonds Hundred And Ten Six [Member] | Taiwan [member] | Tranche D [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 1,600.0  
Domestic Unsecured Bonds Hundred And Ten Seven [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2021-12  
Issuance ending period 2026-12  
Coupon Rate 0.65% 0.65%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Seven [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2021-12  
Issuance ending period 2027-06  
Coupon Rate 0.675% 0.675%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Seven [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2021-12  
Issuance ending period 2028-12  
Coupon Rate 0.72% 0.72%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Seven [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 7,700.0  
Domestic Unsecured Bonds Hundred And Ten Seven [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 3,500.0  
Domestic Unsecured Bonds Hundred And Ten Seven [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 5,500.0  
Domestic Unsecured Bonds Hundred And Ten Five [Member]    
Bonds payable [line items]    
Issuance starting period 2021-09  
Issuance ending period 2051-09  
Coupon Rate 3.10% 3.10%
Repayment and Interest Payment Bullet repayment (callable on the 5th anniversary of the issue date and every anniversary thereafter); interest payable annually  
Domestic Unsecured Bonds Hundred And Ten Five [Member] | Taiwan [member]    
Bonds payable [line items]    
Domestic unsecured bonds   $ 1,000.0
Domestic Unsecured Bonds Hundred And Fourteen One [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2025-03  
Issuance ending period 2030-03  
Coupon Rate 1.90% 1.90%
Domestic unsecured bonds   $ 12,000.0
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Fourteen One [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2025-03  
Issuance ending period 2035-03  
Coupon Rate 2.05% 2.05%
Domestic unsecured bonds   $ 7,200.0
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven One Green Bond [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2022-01  
Issuance ending period 2027-01  
Coupon Rate 0.63% 0.63%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven One Green Bond [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2022-01  
Issuance ending period 2029-01  
Coupon Rate 0.72% 0.72%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven One Green Bond [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 2,100.0  
Domestic Unsecured Bonds Hundred And Eleven One Green Bond [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 3,300.0  
Domestic Unsecured Bonds Hundred And Eleven Two [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2022-03  
Issuance ending period 2026-09  
Coupon Rate 0.84% 0.84%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Two [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2022-03  
Issuance ending period 2027-03  
Coupon Rate 0.85% 0.85%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Two [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2022-03  
Issuance ending period 2029-03  
Coupon Rate 0.90% 0.90%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Two [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 3,000.0  
Domestic Unsecured Bonds Hundred And Eleven Two [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 9,600.0  
Domestic Unsecured Bonds Hundred And Eleven Two [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 1,600.0  
Domestic Unsecured Bonds Hundred And Eleven Three Green Bond [Member]    
Bonds payable [line items]    
Issuance starting period 2022-05  
Issuance ending period 2027-05  
Coupon Rate 1.50% 1.50%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Three Green Bond [Member] | Taiwan [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 6,100.0  
Domestic Unsecured Bonds Hundred And Eleven Four Green Bond [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2022-07  
Issuance ending period 2026-07  
Coupon Rate 1.60% 1.60%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Four Green Bond [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2022-07  
Issuance ending period 2027-07  
Coupon Rate 1.70% 1.70%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Four Green Bond [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2022-07  
Issuance ending period 2029-07  
Coupon Rate 1.75% 1.75%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Four Green Bond [Member] | Tranche D [member]    
Bonds payable [line items]    
Issuance starting period 2022-07  
Issuance ending period 2032-07  
Coupon Rate 1.95% 1.95%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Four Green Bond [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 1,200.0  
Domestic Unsecured Bonds Hundred And Eleven Four Green Bond [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 10,100.0  
Domestic Unsecured Bonds Hundred And Eleven Four Green Bond [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds 1,200.0  
Domestic Unsecured Bonds Hundred And Eleven Four Green Bond [Member] | Taiwan [member] | Tranche D [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 1,400.0  
Domestic Unsecured Bonds Hundred And Eleven Five [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2022-08  
Issuance ending period 2027-06  
Coupon Rate 1.65% 1.65%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Five [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2022-08  
Issuance ending period 2027-08  
Coupon Rate 1.65% 1.65%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Five [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2022-08  
Issuance ending period 2029-08  
Coupon Rate 1.65% 1.65%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Five [Member] | Tranche D [member]    
Bonds payable [line items]    
Issuance starting period 2022-08  
Issuance ending period 2032-08  
Coupon Rate 1.82% 1.82%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Five [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 2,000.0  
Domestic Unsecured Bonds Hundred And Eleven Five [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 8,900.0  
Domestic Unsecured Bonds Hundred And Eleven Five [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds 2,200.0  
Domestic Unsecured Bonds Hundred And Eleven Five [Member] | Taiwan [member] | Tranche D [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 2,500.0  
Domestic Unsecured Bonds Hundred And Eleven Six Green Bond [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2022-10  
Issuance ending period 2027-10  
Coupon Rate 1.75% 1.75%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Six Green Bond [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2022-10  
Issuance ending period 2029-10  
Coupon Rate 1.80% 1.80%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Six Green Bond [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2022-10  
Issuance ending period 2032-10  
Coupon Rate 2.00% 2.00%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Eleven Six Green Bond [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 5,700.0  
Domestic Unsecured Bonds Hundred And Eleven Six Green Bond [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 1,000.0  
Domestic Unsecured Bonds Hundred And Eleven Six Green Bond [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 3,500.0  
Domestic Unsecured Bonds Hundred And Twelve One Green Bond [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2023-03  
Issuance ending period 2028-03  
Coupon Rate 1.54% 1.54%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve One Green Bond [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2023-03  
Issuance ending period 2030-03  
Coupon Rate 1.60% 1.60%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve One Green Bond [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2023-03  
Issuance ending period 2033-03  
Coupon Rate 1.78% 1.78%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve One Green Bond [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 12,200.0  
Domestic Unsecured Bonds Hundred And Twelve One Green Bond [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 2,300.0  
Domestic Unsecured Bonds Hundred And Twelve One Green Bond [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,800.0  
Domestic Unsecured Bonds Hundred And Twelve Two Green Bond [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2023-05  
Issuance ending period 2028-05  
Coupon Rate 1.60% 1.60%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Two Green Bond [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2023-05  
Issuance ending period 2030-05  
Coupon Rate 1.65% 1.65%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Two Green Bond [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2023-05  
Issuance ending period 2033-05  
Coupon Rate 1.82% 1.82%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Two Green Bond [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 13,100.0  
Domestic Unsecured Bonds Hundred And Twelve Two Green Bond [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 2,300.0  
Domestic Unsecured Bonds Hundred And Twelve Two Green Bond [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 5,300.0  
Domestic Unsecured Bonds Hundred And Twelve Three [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2023-06  
Issuance ending period 2028-06  
Coupon Rate 1.60% 1.60%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Three [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2023-06  
Issuance ending period 2030-06  
Coupon Rate 1.65% 1.65%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Three [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2023-06  
Issuance ending period 2033-06  
Coupon Rate 1.80% 1.80%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Three [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 11,400.0  
Domestic Unsecured Bonds Hundred And Twelve Three [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 2,600.0  
Domestic Unsecured Bonds Hundred And Twelve Three [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 6,000.0  
Domestic Unsecured Bonds Hundred And Twelve Four [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2023-08  
Issuance ending period 2028-08  
Coupon Rate 1.60% 1.60%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Four [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2023-08  
Issuance ending period 2030-08  
Coupon Rate 1.65% 1.65%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Four [Member] | Tranche C [member]    
Bonds payable [line items]    
Issuance starting period 2023-08  
Issuance ending period 2033-08  
Coupon Rate 1.76% 1.76%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Four [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 7,300.0  
Domestic Unsecured Bonds Hundred And Twelve Four [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds 700.0  
Domestic Unsecured Bonds Hundred And Twelve Four [Member] | Taiwan [member] | Tranche C [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 7,900.0  
Domestic Unsecured Bonds Hundred And Twelve Five [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2023-10  
Issuance ending period 2028-10  
Coupon Rate 1.62% 1.62%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Five [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2023-10  
Issuance ending period 2033-10  
Coupon Rate 1.76% 1.76%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Twelve Five [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,300.0  
Domestic Unsecured Bonds Hundred And Twelve Five [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 5,500.0  
Domestic Unsecured Bonds Hundred And Thirteen One Green Bond [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2024-03  
Issuance ending period 2029-03  
Coupon Rate 1.64% 1.64%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Thirteen One Green Bond [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2024-03  
Issuance ending period 2034-03  
Coupon Rate 1.76% 1.76%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Thirteen One Green Bond [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 12,000.0  
Domestic Unsecured Bonds Hundred And Thirteen One Green Bond [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 10,800.0  
Domestic Unsecured Bonds Hundred And Thirteen Two Green Bond [Member] | Tranche A [member]    
Bonds payable [line items]    
Issuance starting period 2024-05  
Issuance ending period 2029-05  
Coupon Rate 1.98% 1.98%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Thirteen Two Green Bond [Member] | Tranche B [member]    
Bonds payable [line items]    
Issuance starting period 2024-05  
Issuance ending period 2034-05  
Coupon Rate 2.10% 2.10%
Repayment and Interest Payment Bullet repayment; interest payable annually  
Domestic Unsecured Bonds Hundred And Thirteen Two Green Bond [Member] | Taiwan [member] | Tranche A [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 4,900.0  
Domestic Unsecured Bonds Hundred And Thirteen Two Green Bond [Member] | Taiwan [member] | Tranche B [member]    
Bonds payable [line items]    
Domestic unsecured bonds $ 6,600.0