Variable Interest Entities (Schedule of Aggregate Assets, Liabilities, and Our Exposure to Loss from those VIEs) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Variable Interest Entity [Line Items]
Assets	$ 37,877,577	$ 37,196,124
Total liabilities	32,634,983	31,867,653
Variable Interest Entity Not Primary Beneficiary [Member] | Debt and equity [member]
Variable Interest Entity [Line Items]
Assets	737,516	791,111
Total liabilities	275,110	297,555
Gain (Loss) on Price Risk Derivatives, Net	27,627	14,776
Variable Interest Entity Not Primary Beneficiary [Member] | Miscellaneous Investments [Member]
Variable Interest Entity [Line Items]
Assets	401,245	388,408
Total liabilities	274,342	296,375
Gain (Loss) on Price Risk Derivatives, Net	27,627	14,776
Variable Interest Entity Not Primary Beneficiary [Member] | Partnership Interest [Member]
Variable Interest Entity [Line Items]
Assets	336,271	402,703
Total liabilities	768	1,180
Gain (Loss) on Price Risk Derivatives, Net	$ 0	$ 0