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, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted Average Discount Rate [Line Items]
Liability for unpaid losses and loss adjustment expenses, at undiscounted amounts	$ 1,331	$ 1,387	$ 1,504
Less: amount of discount	388	410	483
Carrying value of liability for unpaid losses and loss adjustment expenses	943	977	1,021
Discount accretion included in losses and loss adjustment expenses	$ 40	$ 30	$ 29
Weighted average discount rate	2.98%	3.06%	3.11%
Minimum
Weighted Average Discount Rate [Line Items]
Range of discount rates	1.77%	1.77%	1.77%
Maximum
Weighted Average Discount Rate [Line Items]
Range of discount rates	14.15%	14.15%	14.15%