Investments (Equity Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Equity Securities	$ 1,440	$ 2,513
Percentage of Available-for-sale Equity Securities	100.00%	100.00%
Federal Home Loan Bank Stock	$ 793	$ 792
Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Equity Securities	1,440	2,513
Common Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Equity Securities	$ 1,037	$ 2,035
Percentage of Available-for-sale Equity Securities	72.00%	81.00%
Nonredeemable Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Equity Securities	$ 403	$ 478
Percentage of Available-for-sale Equity Securities	28.00%	19.00%