Long-Term Debt (Schedule of Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Long-term debt	$ 19,362	$ 19,114
Senior Notes 3.38% Due 2013 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	3.38%
Debt instrument, year of maturity	Dec. 31, 2013
Long-term debt	500	500
Senior Notes 5.70% Due 2014 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	5.70%
Debt instrument, year of maturity	Dec. 31, 2014
Long-term debt	510	510
Senior Notes 2.05% Due 2014 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	2.05%
Debt instrument, year of maturity	Dec. 31, 2014
Long-term debt	700	700
Floating Rate Senior Notes Due 2014 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Debt instrument, year of maturity	Dec. 31, 2014
Long-term debt	300	300
Effective interest rate on floating rate notes	0.98%
Senior Notes 3.95% Due 2016 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	3.95%
Debt instrument, year of maturity	Dec. 31, 2016
Long-term debt	500	500
Senior Notes 3.20% Due 2016 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	3.20%
Debt instrument, year of maturity	Dec. 31, 2016
Long-term debt	999	999
Senior Notes 2.15% Due 2017 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	2.15%
Debt instrument, year of maturity	Dec. 31, 2017
Long-term debt	749	748
Senior Notes 1.60% Due 2017 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	1.60%
Debt instrument, year of maturity	Dec. 31, 2017
Long-term debt	749	749
Senior Notes 1.45% Due 2018 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	1.45%
Debt instrument, year of maturity	Dec. 31, 2018
Long-term debt	499	499
Floating Rate Senior Notes Due 2018 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Debt instrument, year of maturity	Dec. 31, 2018
Long-term debt	400
Effective interest rate on floating rate notes	1.13%
Senior Notes 2.05% Due 2018 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	2.05%
Debt instrument, year of maturity	Dec. 31, 2018
Long-term debt	599
Senior Notes 6.85% Due 2019 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	6.85%
Debt instrument, year of maturity	Dec. 31, 2019
Long-term debt	539	539
Subordinated Notes 5.20% Due 2015 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	5.20%
Debt instrument, year of maturity	Dec. 31, 2015
Long-term debt	933	933
Subordinated Notes 4.90% Due 2017 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	4.90%
Debt instrument, year of maturity	Dec. 31, 2017
Long-term debt	347	345
Subordinated Notes 5.25% Due 2019 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	5.25%
Debt instrument, year of maturity	Dec. 31, 2019
Long-term debt	586	586
Subordinated Notes 3.95% Due 2022 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	3.95%
Debt instrument, year of maturity	Dec. 31, 2022
Long-term debt	298	298
FloatingRateSeniorNotesDue2016Member [Member] | Branch Bank [Member]
Debt Instrument [Line Items]
Debt instrument, year of maturity	Dec. 31, 2016
Long-term debt	125
Effective interest rate on floating rate notes	0.70%
Subordinated Notes 4.88% Due 2013 [Member] | Branch Bank [Member]
Debt Instrument [Line Items]
Interest Rate	4.88%
Debt instrument, year of maturity	Dec. 31, 2013
Long-term debt	0	222
Subordinated Notes 5.63% Due 2016 [Member] | Branch Bank [Member]
Debt Instrument [Line Items]
Interest Rate	5.63%
Debt instrument, year of maturity	Dec. 31, 2016
Long-term debt	386	386
Floating Rate Subordinated Notes Due 2016 [Member] | Branch Bank [Member]
Debt Instrument [Line Items]
Debt instrument, year of maturity	Dec. 31, 2016
Long-term debt	350	350
Floating Rate Subordinated Notes Due 2017 [Member] | Branch Bank [Member]
Debt Instrument [Line Items]
Debt instrument, year of maturity	Dec. 31, 2017
Long-term debt	262	262
Varying maturities to 2034 [Member] | Federal Home Loan Bank Advances to Branch Bank [Member]
Debt Instrument [Line Items]
Debt instrument, year of maturity	Dec. 31, 2034
Long-term debt	8,462	8,994
Other Long-Term Debt [Member]
Debt Instrument [Line Items]
Long-term debt	103	100
Fair Value Hedge-Related Basis Adjustments [Member]
Debt Instrument [Line Items]
Long-term debt	$ 466	$ 594