Other Comprehensive Income and Accumulated Other Comprehensive Income (details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 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	(314)
Amounts reclassified from accumulated other comprehensive income	4
Net other comprehensive income, current period	(310)	34
Accumulated other comprehensive income, net of tax, balance, end of period	1,926	2,039
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income	(376)	(77)
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income	9	25
Net changes in benefit plan assets and obligations	28	20
Net changes in unrealized foreign currency translation	(96)	64
Other comprehensive income (loss) before income taxes	(435)	32
Income tax expense (benefit), other comprehensive income	(125)	(2)
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	(234)
Amounts reclassified from accumulated other comprehensive income	(11)
Net other comprehensive income, current period	(245)	(50)
Accumulated other comprehensive income, net of tax, balance, end of period	2,663
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income	(376)	(77)
Income tax expense (benefit), other comprehensive income	(131)	(27)
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	5
Amounts reclassified from accumulated other comprehensive income	1
Net other comprehensive income, current period	6	16
Accumulated other comprehensive income, net of tax, balance, end of period	201
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income	9	25
Income tax expense (benefit), other comprehensive income	3	9
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	17
Net other comprehensive income, current period	18	13
Accumulated other comprehensive income, net of tax, balance, end of period	(839)
Net changes in benefit plan assets and obligations	28	20
Income tax expense (benefit), other comprehensive income	10	7
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	(86)
Amounts reclassified from accumulated other comprehensive income	(3)
Net other comprehensive income, current period	(89)	55
Accumulated other comprehensive income, net of tax, balance, end of period	(99)
Net changes in unrealized foreign currency translation	(96)	64
Income tax expense (benefit), other comprehensive income	$ (7)	$ 9