Contingencies, Commitments and Guarantees (Insolvency Assessments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Other Assets:
Premium tax offset for future discounted and undiscounted assessments	$ 47	$ 56
Premium tax offset currently available for paid assessments	46	50
Other Liabilities:
Insolvency assessments	67	75
Insurance-related Assessments
Other Assets:
Total assets held for insolvency assessments	$ 93	$ 106