Reserve for Unpaid Losses and Loss Adjustment Expenses - Discounted Reserves, P&C (Details) - Property and Casualty Insurance Products - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted Average Discount Rate [Line Items]
Liability for unpaid losses and loss adjustment expenses, at undiscounted amounts	$ 1,331	$ 1,331	$ 1,387
Amount of discount	388	388	410
Carrying value of liability for unpaid losses and loss adjustment expenses	943	943	977
Discount accretion included in losses and loss adjustment expenses	$ 33	$ 40	$ 30
Financial Guarantee Insurance Contracts, Claim Liability, Weighted Average Risk Free Discount Rate	2.91%	2.98%	3.06%
Minimum
Weighted Average Discount Rate [Line Items]
Range of discount rates	1.76%	1.77%	1.77%
Maximum
Weighted Average Discount Rate [Line Items]
Range of discount rates	14.03%	14.15%	14.15%