Contingencies, Commitments and Guarantees (Insolvency Assessments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Other Assets:
Premium tax offset for future discounted and undiscounted assessments	$ 40	$ 43
Premium tax offset currently available for paid assessments	35	43
Other Liabilities:
Insolvency assessments	60	62
Insurance-related Assessments
Other Assets:
Total assets held for insolvency assessments	$ 75	$ 86