Financial Instruments (Offsetting of Financial Assets and Financial Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Offsetting of Assets
Gross Amounts of Recognized Assets	$ 554	$ 397
Gross Amounts Offset in the Consolidated Balance Sheets	(45)	(32)
Net Presented in the Consolidated Balance Sheets	509	365
Financial Instruments	(208)	(295)
Cash Collateral Received	(190)	(16)
Non-Cash Collateral Received	0	0
Net Assets Exposed	111	54
Offsetting of Liabilities
Gross Amounts of Recognized Liabilities	400	1,554
Gross Amounts Offset in the Consolidated Balance Sheets	(45)	(32)
Net Presented in the Consolidated Balance Sheets	355	1,522
Financial Instruments	(208)	(295)
Cash Collateral Pledged	(2)	(1)
Non-Cash Collateral Pledged	(86)	(943)
Net Liabilities	$ 59	$ 283