Long-Term Debt (Schedule of Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Long-term debt	$ 19,221		$ 21,803
Junior Subordinated Debt to Unconsolidated Trusts [Member]
Debt Instrument [Line Items]
Long-term debt	57	[1]	3,271	[1]
Senior Notes 3.85% Due 2012 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	3.85%
Debt instrument, year of maturity	Dec. 31, 2012
Long-term debt	0		1,000
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	[2]	300	[2]
Effective interest rate on floating rate notes	1.15%
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	499		499
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	748		0
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		0
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		538
Subordinated Notes 4.75% Due 2012 [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Interest Rate	4.75%
Debt instrument, year of maturity	Dec. 31, 2012
Long-term debt	491	[3]	490	[3]
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	[3]	933	[3]
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	344	[3]	342	[3]
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	[3]	586	[3]
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	[3]	0	[3]
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	[3],[4]	350	[3],[4]
Effective interest rate on floating rate notes	3.26%
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	[3],[4]	262	[3],[4]
Effective interest rate on floating rate notes	3.26%
Subordinated Notes 4.875% Due 2013 [Member] | Branch Bank [Member]
Debt Instrument [Line Items]
Interest Rate	4.875%
Debt instrument, year of maturity	Dec. 31, 2013
Long-term debt	222	[3]	222	[3]
Subordinated Notes 5.625% Due 2016 [Member] | Branch Bank [Member]
Debt Instrument [Line Items]
Interest Rate	5.625%
Debt instrument, year of maturity	Dec. 31, 2016
Long-term debt	386	[3]	386	[3]
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	8,993	[5]	8,998	[5]
Federal Home Loan Bank advances weighted average cost	3.58%
Federal Home Loan Bank advances weighted average maturity (in years)	7.1
Other Long-Term Debt [Member]
Debt Instrument [Line Items]
Long-term debt	125		83
Fair Value Hedge-Related Basis Adjustments [Member]
Debt Instrument [Line Items]
Long-term debt	$ 630		$ 834

[1] Securities that qualify under the risk-based capital guidelines as Tier 1 capital, subject to certain limitations. Once notice of redemption has been given, they no longer qualify as Tier 1 capital.

[2] These floating-rate senior notes are based on LIBOR and had an effective rate of 1.15% at September 30, 2012.

[3] Subordinated notes that qualify under the risk-based capital guidelines as Tier 2 supplementary capital, subject to certain limitations.

[4] These floating-rate securities are based on LIBOR, but the majority of the cash flows have been swapped to a fixed rate. The effective rate paid on these securities including the effect of the swapped portion was 3.26% at September 30, 2012.

[5] Certain of these advances have been swapped to floating rates from fixed rates and from fixed rates to floating rates. At September 30, 2012, the weighted average rate paid on these advances including the effect of the swapped portion was 3.58%, and the weighted average maturity was 7.1 years.