Other Comprehensive Income and Accumulated Other Comprehensive Income (details) - Reclassifications (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Income tax (expense) benefit	$ 324	$ 271
Amounts reclassified from accumulated other comprehensive income, net of taxes	4
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive income, before tax	8
Income tax (expense) benefit	4
Amounts reclassified from accumulated other comprehensive income, net of taxes	4
Changes in Net Unrealized Gains on Investment Securities Having No Credit Losses Recognized in the Consolidated Statement of Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive income, net of taxes	(11)
Changes in Net Unrealized Gains on Investment Securities Having No Credit Losses Recognized in the Consolidated Statement of Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive income, before tax	(17)
Income tax (expense) benefit	(6)
Amounts reclassified from accumulated other comprehensive income, net of taxes	(11)
Changes in Net Unrealized Gains on Investment Securities Having Credit Losses Recognized in the Consolidated Statement of Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive income, net of taxes	1
Changes in Net Unrealized Gains on Investment Securities Having Credit Losses Recognized in the Consolidated Statement of Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive income, before tax	1
Amounts reclassified from accumulated other comprehensive income, net of taxes	1
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive income, net of taxes	17
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive income, before tax	27
Income tax (expense) benefit	10
Amounts reclassified from accumulated other comprehensive income, net of taxes	17
Net Unrealized Foreign Currency Translation [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive income, net of taxes	(3)
Net Unrealized Foreign Currency Translation [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive income, before tax	(3)
Amounts reclassified from accumulated other comprehensive income, net of taxes	$ (3)