Netting Arrangements (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Assets:
Derivative assets, gross amount	$ 1,099	$ 1,951
Derivative assets, gross amount offset	(290)	(905)
Derivative assets, net amount presented in our condensed consolidated balance sheets	809	1,046
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	(323)	(406)
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	(2)	(53)
Derivative assets, net amount	484	587
Securities purchased under agreements to resell or similar arrangements, gross amount	87,010	46,644
Securities purchased under agreements to resell or similar arrangements, gross amount offset	0	0
Securities purchased under agreements to resell or similar arrangements, under master netting arrangements,	87,010	46,644
Securities purchased under agreements to resell or similar arrangements, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	0	0
Securities purchased under agreements to resell or similar arrangements, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	(87,010)	(46,644)
Securities purchased under agreements to resell or similar arrangements, net amount	0	0
Total assets, gross amount	88,109	48,595
Total assets, gross amount offset	(290)	(905)
Total assets, net amount presented in our condensed consolidated balance sheets	87,819	47,690
Total assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	(323)	(406)
Total assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	(87,012)	(46,697)
Total assets, net amount	484	587
Liabilities:
Derivative liabilities, gross amount	(1,440)	(2,441)
Derivative liabilities, gross amount offset	838	995
Derivative liabilities, net amount presented in our condensed consolidated balance sheets	(602)	(1,446)
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	323	406
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	11	1,019
Derivative liabilities, net amount	(268)	(21)
Securities sold under agreements to repurchase or similar arrangements, gross	(363)	0
Total liabilities, gross amount	(1,803)	(2,441)
Total liabilities, gross amount offset	838	995
Securities sold under agreements to repurchase or similar arrangements, net amount presented in our condensed consolidated balance sheets	(363)	0
Total liabilities, net amount presented in our condensed consolidated balance sheets	(965)	(1,446)
Total liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	323	406
Securities sold under agreements to repurchase or similar arrangements, collateral	363	0
Total liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	374	1,019
Securities sold under agreements to repurchase or similar arrangements, net amount	0	0
Total liabilities, net amount	(268)	(21)
Risk Management Derivatives
Assets:
Derivative assets, gross amount offset	(290)	(905)
Liabilities:
Derivative liabilities, gross amount offset	838	995
Mortgage commitment derivatives
Assets:
Derivative assets, gross amount	763	989
Derivative assets, gross amount offset	0	0
Derivative assets, net amount presented in our condensed consolidated balance sheets	763	989
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	(323)	(406)
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	(2)	(53)
Derivative assets, net amount	438	530
Liabilities:
Derivative liabilities, gross amount	(599)	(1,426)
Derivative liabilities, gross amount offset	0	0
Derivative liabilities, net amount presented in our condensed consolidated balance sheets	(599)	(1,426)
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	323	406
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	11	1,017
Derivative liabilities, net amount	(265)	(3)
Over the Counter | Risk Management Derivatives
Assets:
Derivative assets, gross amount	336	962
Derivative assets, gross amount offset	(331)	(952)
Derivative assets, net amount presented in our condensed consolidated balance sheets	5	10
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	0	0
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	0	0
Derivative assets, net amount	5	10
Liabilities:
Derivative liabilities, gross amount	(841)	(1,015)
Derivative liabilities, gross amount offset	838	999
Derivative liabilities, net amount presented in our condensed consolidated balance sheets	(3)	(16)
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	0	0
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	0	0
Derivative liabilities, net amount	(3)	(16)
Exchange Cleared | Risk Management Derivatives
Assets:
Derivative assets, gross amount	0	0
Derivative assets, gross amount offset	41	47
Derivative assets, net amount presented in our condensed consolidated balance sheets	41	47
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	0	0
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	0	0
Derivative assets, net amount	41	47
Liabilities:
Derivative liabilities, gross amount	0	0
Derivative liabilities, gross amount offset	0	(4)
Derivative liabilities, net amount presented in our condensed consolidated balance sheets	0	(4)
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	0	0
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	0	2
Derivative liabilities, net amount	$ 0	$ (2)