Netting Arrangements (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Assets:
Derivative assets, gross amount	$ 676	$ 1,951
Derivative assets, gross amount offset	(331)	(905)
Derivative assets, net amount presented in our condensed consolidated balance sheets	345	1,046
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	(182)	(406)
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	0	(53)
Derivative assets, net amount	163	587
Securities purchased under agreements to resell or similar arrangements, gross amount	90,838	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,	90,838	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	(90,838)	(46,644)
Securities purchased under agreements to resell or similar arrangements, net amount	0	0
Total assets, gross amount	91,514	48,595
Total assets, gross amount offset	(331)	(905)
Total assets, net amount presented in our condensed consolidated balance sheets	91,183	47,690
Total assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	(182)	(406)
Total assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	(90,838)	(46,697)
Total assets, net amount	163	587
Liabilities:
Derivative liabilities, gross amount	(1,335)	(2,441)
Derivative liabilities, gross amount offset	849	995
Derivative liabilities, net amount presented in our condensed consolidated balance sheets	(486)	(1,446)
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	182	406
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	295	1,019
Derivative liabilities, net amount	(9)	(21)
Total liabilities, gross amount	(1,335)	(2,441)
Total liabilities, gross amount offset	849	995
Total liabilities, net amount presented in our condensed consolidated balance sheets	(486)	(1,446)
Total liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	182	406
Total liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	295	1,019
Total liabilities, net amount	(9)	(21)
Risk Management Derivatives
Assets:
Derivative assets, gross amount offset	(331)	(905)
Liabilities:
Derivative liabilities, gross amount offset	849	995
Mortgage commitment derivatives
Assets:
Derivative assets, gross amount	311	989
Derivative assets, gross amount offset	0	0
Derivative assets, net amount presented in our condensed consolidated balance sheets	311	989
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	(182)	(406)
Derivative assets, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	0	(53)
Derivative assets, net amount	129	530
Liabilities:
Derivative liabilities, gross amount	(476)	(1,426)
Derivative liabilities, gross amount offset	0	0
Derivative liabilities, net amount presented in our condensed consolidated balance sheets	(476)	(1,426)
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, financial instruments	182	406
Derivative liabilities, under master netting arrangements, amounts not offset in our condensed consolidated balance sheets, collateral	288	1,017
Derivative liabilities, net amount	(6)	(3)
Over the Counter | Risk Management Derivatives
Assets:
Derivative assets, gross amount	365	962
Derivative assets, gross amount offset	(348)	(952)
Derivative assets, net amount presented in our condensed consolidated balance sheets	17	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	17	10
Liabilities:
Derivative liabilities, gross amount	(859)	(1,015)
Derivative liabilities, gross amount offset	856	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	17	47
Derivative assets, net amount presented in our condensed consolidated balance sheets	17	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	17	47
Liabilities:
Derivative liabilities, gross amount	0	0
Derivative liabilities, gross amount offset	(7)	(4)
Derivative liabilities, net amount presented in our condensed consolidated balance sheets	(7)	(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	7	2
Derivative liabilities, net amount	$ 0	$ (2)