Other Comprehensive Income and Accumulated Other Comprehensive Income (details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accumulated other comprehensive income [Roll Forward]
Accumulated other comprehensive income, net of tax, balance, beginning of year			$ 2,236	$ 2,005
Other comprehensive income (loss) before reclassifications			(1,515)
Amounts reclassified from accumulated other comprehensive income			(1)
Net other comprehensive income (loss), current period	(1,206)	91	(1,516)	125
Accumulated other comprehensive income, net of tax, balance, end of period	720	2,130	720	2,130
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income	(1,790)	216	(2,166)	139
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income	(5)	5	4	30
Net changes in benefit plan assets and obligations	26	22	54	42
Net changes in unrealized foreign currency translation	(73)	(86)	(169)	(22)
Other comprehensive income (loss) before income taxes	(1,842)	157	(2,277)	189
Income tax expense (benefit), other comprehensive income (loss)	(636)	66	(761)	64
Changes in Net Unrealized Gains on Investment Securities Having No Credit Losses Recognized in the Consolidated Statement of Income [Member]
Accumulated other comprehensive income [Roll Forward]
Accumulated other comprehensive income, net of tax, balance, beginning of year			2,908
Other comprehensive income (loss) before reclassifications			(1,381)
Amounts reclassified from accumulated other comprehensive income			(33)
Net other comprehensive income (loss), current period	(1,169)	139	(1,414)	89
Accumulated other comprehensive income, net of tax, balance, end of period	1,494		1,494
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income	(1,790)	216	(2,166)	139
Income tax expense (benefit), other comprehensive income (loss)	(621)	77	(752)	50
Changes in Net Unrealized Gains on Investment Securities Having Credit Losses Recognized in the Consolidated Statement of Income [Member]
Accumulated other comprehensive income [Roll Forward]
Accumulated other comprehensive income, net of tax, balance, beginning of year			195
Other comprehensive income (loss) before reclassifications			2
Amounts reclassified from accumulated other comprehensive income			1
Net other comprehensive income (loss), current period	(3)	4	3	20
Accumulated other comprehensive income, net of tax, balance, end of period	198		198
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income	(5)	5	4	30
Income tax expense (benefit), other comprehensive income (loss)	(2)	1	1	10
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member]
Accumulated other comprehensive income [Roll Forward]
Accumulated other comprehensive income, net of tax, balance, beginning of year			(857)
Other comprehensive income (loss) before reclassifications			1
Amounts reclassified from accumulated other comprehensive income			34
Net other comprehensive income (loss), current period	17	14	35	27
Accumulated other comprehensive income, net of tax, balance, end of period	(822)		(822)
Net changes in benefit plan assets and obligations	26	22	54	42
Income tax expense (benefit), other comprehensive income (loss)	9	8	19	15
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income [Roll Forward]
Accumulated other comprehensive income, net of tax, balance, beginning of year			(10)
Other comprehensive income (loss) before reclassifications			(137)
Amounts reclassified from accumulated other comprehensive income			(3)
Net other comprehensive income (loss), current period	(51)	(66)	(140)	(11)
Accumulated other comprehensive income, net of tax, balance, end of period	(150)		(150)
Net changes in unrealized foreign currency translation	(73)	(86)	(169)	(22)
Income tax expense (benefit), other comprehensive income (loss)	$ (22)	$ (20)	$ (29)	$ (11)