Fair value measurements (Carrying Values And Fair Values Of Financial Instruments Not Measured At Fair Value) (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Private debt held-for-investment	$ 2,429	$ 2,628
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	3,059	2,731
Short-term debt	1,499	800
Long-term debt	13,477	14,379
Hybrid debt	420	419
Portion at Other than Fair Value Measurement | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Private debt held-for-investment	0	0
Assets, Fair Value Disclosure	0	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	0	0
Short-Term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Hybrid debt, Fair Value	0	0
Liabilities, Fair Value Disclosure	0	0
Portion at Other than Fair Value Measurement | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Private debt held-for-investment	0	0
Assets, Fair Value Disclosure	0	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	3,059	2,731
Short-Term Debt, Fair Value	1,488	797
Long-term Debt, Fair Value	12,025	12,979
Hybrid debt, Fair Value	479	479
Liabilities, Fair Value Disclosure	17,051	16,986
Portion at Other than Fair Value Measurement | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Private debt held-for-investment	2,472	2,680
Assets, Fair Value Disclosure	2,472	2,680
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	0	0
Short-Term Debt, Fair Value	0	0
Long-term Debt, Fair Value	254	0
Hybrid debt, Fair Value	0	0
Liabilities, Fair Value Disclosure	254	0
Portion at Other than Fair Value Measurement | Total Level 1, Level 2, and Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Private debt held-for-investment	2,472	2,680
Assets, Fair Value Disclosure	2,472	2,680
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	3,059	2,731
Short-Term Debt, Fair Value	1,488	797
Long-term Debt, Fair Value	12,279	12,979
Hybrid debt, Fair Value	479	479
Liabilities, Fair Value Disclosure	17,305	16,986
Reported Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Private debt held-for-investment	2,429	2,628
Assets, Fair Value Disclosure	2,429	2,628
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	3,059	2,731
Short-term debt	1,499	800
Long-term debt	13,477	14,379
Hybrid debt	420	419
Liabilities, Fair Value Disclosure	$ 18,455	$ 18,329