Derivatives and Hedging Activities - Schedule of FHLBNY’s Derivative Activities Based on Notional Amounts (Details) - USD ($) $ in Thousands |
Sep. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Derivative [Line Items] | ||
| Total interest rate contracts notionals | $ 181,220,832 | $ 198,855,637 |
| Interest rate swaps | ||
| Derivative [Line Items] | ||
| Total interest rate contracts notionals | 176,452,016 | 197,819,179 |
| Interest rate caps | ||
| Derivative [Line Items] | ||
| Total interest rate contracts notionals | 4,710,000 | 1,000,000 |
| Mortgage delivery commitments | ||
| Derivative [Line Items] | ||
| Total interest rate contracts notionals | $ 58,816 | $ 36,458 |