Derivative Financial Instruments - Offsetting Derivative Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Assets:
Gross Amount Recognized in the Consolidated Balance Sheets, Derivatives	$ 2,862	$ 1,655
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets, Derivatives	(621)	(417)
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets, Collateral	(755)	(504)
Net Amount, Derivatives	1,486	734
Recognized in the Condensed Consolidated Balance Sheets, Total assets	2,862	1,655
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets, Derivatives, Total assets	(621)	(417)
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets, Collateral, Total assets	(755)	(504)
Net Amount, Total assets	1,486	734
Liabilities:
Gross Amount Recognized in the Condensed Consolidated Balance Sheets, Derivatives	1,072	741
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets, Derivatives	(621)	(417)
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets, Collateral	(221)	(97)
Net Amount	230	227
Recognized in the Condensed Consolidated Balance Sheets, Total liabilities	1,072	741
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets, Derivatives, Total liabilities	(621)	(417)
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets, Collateral, Total liabilities	(221)	(97)
Net Amount, Total liabilities	$ 230	$ 227