v3.26.1
Investments - Schedule on Plan's Investment Assets At Fair Value (Detail) - EBP 001 [Member] - USD ($)
Dec. 31, 2025
Dec. 31, 2024
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value $ 37,314,403 $ 30,958,251
Mutual Fund [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 35,920,873 29,820,401
Common Collective Trust [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 140,257 179,484
South Bow Common Stock [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 734,705 425,398
TC Energy Common Stock [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 518,568 532,968
Fair Value, Inputs, Level 1 [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 37,174,146 30,778,767
Fair Value, Inputs, Level 1 [Member] | Mutual Fund [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 35,920,873 29,820,401
Fair Value, Inputs, Level 1 [Member] | Common Collective Trust [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Fair Value, Inputs, Level 1 [Member] | South Bow Common Stock [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 734,705 425,398
Fair Value, Inputs, Level 1 [Member] | TC Energy Common Stock [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 518,568 532,968
Fair Value, Inputs, Level 2 [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Fair Value, Inputs, Level 2 [Member] | Mutual Fund [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Fair Value, Inputs, Level 2 [Member] | Common Collective Trust [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Fair Value, Inputs, Level 2 [Member] | South Bow Common Stock [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Fair Value, Inputs, Level 2 [Member] | TC Energy Common Stock [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Fair Value, Inputs, Level 3 [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | Mutual Fund [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | Common Collective Trust [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | South Bow Common Stock [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | TC Energy Common Stock [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value 0 0
Other    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value [1] 140,257 179,484
Other | Mutual Fund [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value [1] 0 0
Other | Common Collective Trust [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value [1] 140,257 179,484
Other | South Bow Common Stock [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value [1] 0 0
Other | TC Energy Common Stock [Member]    
EBP, Investment, Fair Value and NAV [Line Items]    
EBP, Investment, excluding plan interest in master trust, fair value [1] $ 0 $ 0
[1] Fair value is measured using net asset value as a practical expedient and is therefore excluded from the fair value hierarchy.