Derivative Financial Instruments - Exposure (Details) - USD ($) $ in Millions |
Sep. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Derivative Financial Instruments | ||
| Cash and securities posted under collateral arrangements associated with derivative credit support agreements and Futures Commission Merchant agreements | $ 493.6 | $ 491.1 |
| Aggregate fair value of all derivative instruments with credit-risk-related contingent features that were in a liability position | 664.7 | 546.9 |
| Collateral and initial margin posted supporting derivatives with credit-risk-related contingent features that were in a liability position | 493.6 | 491.1 |
| Additional collateral required to be posted if derivative credit-risk-related contingent features were triggered | 113.1 | |
| Cash collateral received associated with derivative credit support annex agreements and Futures Commission Merchant agreements | $ 1,323.0 | $ 787.6 |