Consolidated Statement of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 733	$ 600
Other comprehensive loss:
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income	(1,596)	(575)
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income	0	(6)
Net changes in benefit plan assets and obligations	25	23
Net changes in unrealized foreign currency translation	26	(268)
Other comprehensive loss before income taxes	(1,545)	(826)
Income tax benefit	(334)	(137)
Other comprehensive loss, net of taxes	(1,211)	(689)
Comprehensive loss	$ (478)	$ (89)