- Fair Values (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	$ 22,004	$ 23,112
Gross unrealized gain	1,355	1,310
Gross unrealized loss	(98)	(200)
Fair value	23,261	24,222
U.S. government and agencies
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	768	968
Gross unrealized gain	38	48
Gross unrealized loss	(2)	(2)
Fair value	804	1,014
Municipal
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	2,001	2,017
Gross unrealized gain	275	264
Gross unrealized loss	(3)	(7)
Fair value	2,273	2,274
Corporate
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	18,262	18,945
Gross unrealized gain	960	905
Gross unrealized loss	(86)	(169)
Fair value	19,136	19,681
Foreign government
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	279	304
Gross unrealized gain	20	28
Gross unrealized loss	0	0
Fair value	299	332
ABS
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	383	337
Gross unrealized gain	6	4
Gross unrealized loss	(4)	(10)
Fair value	385	331
RMBS
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	205	294
Gross unrealized gain	49	42
Gross unrealized loss	(1)	(3)
Fair value	253	333
CMBS
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	93	233
Gross unrealized gain	6	17
Gross unrealized loss	(2)	(9)
Fair value	97	241
Redeemable preferred stock
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	13	14
Gross unrealized gain	1	2
Gross unrealized loss	0	0
Fair value	$ 14	$ 16