Consolidated Statement of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Consolidated Statement of Comprehensive Income
Net income	$ 304	$ 864	$ 499	$ 806	$ 618	$ 333	$ (364)	$ 839	$ 2,473	$ 1,426	$ 3,216
Other comprehensive income:
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income									281	1,570	(118)
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income									81	4	123
Net changes in benefit plan assets and obligations									(69)	(307)	39
Net changes in unrealized foreign currency translation and other changes									43	(90)	12
Other comprehensive income before income taxes									336	1,177	56
Income tax expense									105	427	20
Other comprehensive income, net of taxes									231	750	36
Comprehensive income									$ 2,704	$ 2,176	$ 3,252