Income Tax (Total Income Taxes Provided) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Effects Allocated Directly to Equity [Abstract]
Provision for income taxes	$ 138	$ 262	$ 130
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	611	681	(368)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	(9)	3	19
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	(1)	(5)	0
Income Tax Expense (Benefit), Intraperiod Tax Allocation	$ 739	$ 941	$ (219)