Financial Instruments (Offsetting of Financial Assets and Financial Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Offsetting of Assets
Gross Amounts of Recognized Assets	$ 397	$ 366
Gross Amounts Offset in the Consolidated Balance Sheets	(32)	(21)
Net Presented in the Consolidated Balance Sheets	365	345
Financial Instruments	(295)	(88)
Cash Collateral Received	(16)	(234)
Non-Cash Collateral Received	0	0
Net Assets Exposed	54	23
Offsetting of Liabilities
Gross Amounts of Recognized Liabilities	1,554	403
Gross Amounts Offset in the Consolidated Balance Sheets	(32)	(21)
Net Presented in the Consolidated Balance Sheets	1,522	382
Financial Instruments	(295)	(88)
Cash Collateral Pledged	(1)	0
Non-Cash Collateral Pledged	(943)	0
Net Liabilities	$ 283	$ 294