Quarterly Operating Results (Unaudited) - Realized gains, favorable (adverse) prior year development of the liability for losses and LAE and the impact of derivatives related to Fixed-indexed annuities (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Realized gains (losses) and favorable (adverse) development on unpaid loss and loss adjustment expenses
Realized Gains (Losses) on Securities and Subsidiaries	$ (15)	$ 1	$ 8	$ 2	$ 6	$ (12)	$ 8	$ 3	$ (4)	$ 5
Prior Year Development Favorable (Adverse)	61	31	44	56	66	(52)	22	28	192	64
Impact of derivatives related to FIAs	(47)	(2)	3	13	$ (11)	$ (4)	$ (16)	$ (2)	(33)	$ (33)
Equity securities | Accounting Standards Update 2016-01
Realized gains (losses) and favorable (adverse) development on unpaid loss and loss adjustment expenses
Realized Gains (Losses) on Securities and Subsidiaries	$ (223)	$ 33	$ 23	$ (95)					$ (262)