Long-Term Debt (Schedule of Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended	9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended				9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended			12 Months Ended	9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2012 Senior Notes 3.38% Due 2013 [Member] Parent Company [Member]	Sep. 30, 2013 Senior Notes 5.70% Due 2014 [Member] Parent Company [Member]	Dec. 31, 2012 Senior Notes 5.70% Due 2014 [Member] Parent Company [Member]	Sep. 30, 2013 Senior Notes 2.05% Due 2014 [Member] Parent Company [Member]	Dec. 31, 2012 Senior Notes 2.05% Due 2014 [Member] Parent Company [Member]	Sep. 30, 2013 Floating Rate Senior Notes Due 2014 [Member] Parent Company [Member]	Dec. 31, 2012 Floating Rate Senior Notes Due 2014 [Member] Parent Company [Member]	Sep. 30, 2013 Senior Notes 3.95% Due 2016 [Member] Parent Company [Member]	Dec. 31, 2012 Senior Notes 3.95% Due 2016 [Member] Parent Company [Member]	Sep. 30, 2013 Senior Notes 3.20% Due 2016 [Member] Parent Company [Member]	Dec. 31, 2012 Senior Notes 3.20% Due 2016 [Member] Parent Company [Member]	Sep. 30, 2013 Senior Notes 2.15% Due 2017 [Member] Parent Company [Member]	Dec. 31, 2012 Senior Notes 2.15% Due 2017 [Member] Parent Company [Member]	Sep. 30, 2013 Senior Notes 1.60% Due 2017 [Member] Parent Company [Member]	Dec. 31, 2012 Senior Notes 1.60% Due 2017 [Member] Parent Company [Member]	Sep. 30, 2013 Senior Notes 1.45% Due 2018 [Member] Parent Company [Member]	Dec. 31, 2012 Senior Notes 1.45% Due 2018 [Member] Parent Company [Member]	Sep. 30, 2013 Floating Rate Senior Notes Due 2018 [Member] Parent Company [Member]	Sep. 30, 2013 Senior Notes 2.05% Due 2018 [Member] Parent Company [Member]	Sep. 30, 2013 Senior Notes 6.85% Due 2019 [Member] Parent Company [Member]	Dec. 31, 2012 Senior Notes 6.85% Due 2019 [Member] Parent Company [Member]	Sep. 30, 2013 Subordinated Notes 5.20% Due 2015 [Member] Parent Company [Member]	Dec. 31, 2012 Subordinated Notes 5.20% Due 2015 [Member] Parent Company [Member]	Sep. 30, 2013 Subordinated Notes 4.90% Due 2017 [Member] Parent Company [Member]	Dec. 31, 2012 Subordinated Notes 4.90% Due 2017 [Member] Parent Company [Member]	Sep. 30, 2013 Subordinated Notes 5.25% Due 2019 [Member] Parent Company [Member]	Dec. 31, 2012 Subordinated Notes 5.25% Due 2019 [Member] Parent Company [Member]	Sep. 30, 2013 Subordinated Notes 3.95% Due 2022 [Member] Parent Company [Member]	Dec. 31, 2012 Subordinated Notes 3.95% Due 2022 [Member] Parent Company [Member]	Sep. 30, 2013 Senior Notes 1.45% Due 2016 [Member] Branch Bank [Member]	Sep. 30, 2013 Floating Rate Senior Notes Due 2016 [Member] Branch Bank [Member]	Sep. 30, 2013 Senior Notes 2.30% Due 2018 [Member] Branch Bank [Member]	Dec. 31, 2012 Subordinated Notes 4.88% Due 2013 [Member] Branch Bank [Member]	Sep. 30, 2013 Subordinated Notes 5.63% Due 2016 [Member] Branch Bank [Member]	Dec. 31, 2012 Subordinated Notes 5.63% Due 2016 [Member] Branch Bank [Member]	Sep. 30, 2013 Floating Rate Subordinated Notes Due 2016 [Member] Branch Bank [Member]	Dec. 31, 2012 Floating Rate Subordinated Notes Due 2016 [Member] Branch Bank [Member]	Sep. 30, 2013 Floating Rate Subordinated Notes Due 2017 [Member] Branch Bank [Member]	Dec. 31, 2012 Floating Rate Subordinated Notes Due 2017 [Member] Branch Bank [Member]	Sep. 30, 2013 Varying maturities to 2034 [Member] Federal Home Loan Bank Advances to Branch Bank [Member]	Dec. 31, 2012 Varying maturities to 2034 [Member] Federal Home Loan Bank Advances to Branch Bank [Member]	Sep. 30, 2013 Other Long-Term Debt [Member]	Dec. 31, 2012 Other Long-Term Debt [Member]	Sep. 30, 2013 Fair Value Hedge-Related Basis Adjustments [Member]	Dec. 31, 2012 Fair Value Hedge-Related Basis Adjustments [Member]
Debt Instrument [Line Items]
Long-term debt	$ 20,402	$ 19,114	$ 500	$ 510	$ 510	$ 700	$ 700	$ 300	$ 300	$ 500	$ 500	$ 999	$ 999	$ 749	$ 748	$ 749	$ 749	$ 499	$ 499	$ 400	$ 599	$ 539	$ 539	$ 933	$ 933	$ 348	$ 345	$ 586	$ 586	$ 298	$ 298	$ 750	$ 125	$ 750	$ 222	$ 386	$ 386	$ 350	$ 350	$ 262	$ 262	$ 8,464	$ 8,994	$ 102	$ 100	$ 504	$ 594
Interest Rate			3.38%	5.70%		2.05%				3.95%		3.20%		2.15%		1.60%		1.45%			2.05%	6.85%		5.20%		4.90%		5.25%		3.95%		1.45%		2.30%	4.88%	5.63%
Effective interest rate at period end								0.96%												1.11%													0.67%					3.25%		3.25%
Debt instrument, year of maturity			Dec. 31, 2013	Dec. 31, 2014		Dec. 31, 2014		Dec. 31, 2014		Dec. 31, 2016		Dec. 31, 2016		Dec. 31, 2017		Dec. 31, 2017		Dec. 31, 2018		Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2019		Dec. 31, 2015		Dec. 31, 2017		Dec. 31, 2019		Dec. 31, 2022		Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2013	Dec. 31, 2016		Dec. 31, 2016		Dec. 31, 2017		Dec. 31, 2034