Off-Balance Sheet Lending-Related Financial Instruments, Guarantees and Other Commitments - Standby Letters of Credit and Other Financial Guarantees (Details) - USD ($) $ in Millions	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Total lending-related commitments	$ 935,582		$ 950,997	$ 1,041,373
Allowance for lending-related commitments	231	$ 252	275	$ 436	$ 564	$ 681
Derivatives qualifying as guarantees
Derivative, notional amount	53,708,000		63,662,000
Standby and Other Letters of Credit
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Standby and other letters of credit, carrying value	752		789
Standby and other letters of credit, allowance	278		235
Guarantor obligations, current carrying value	474		554
Standby letters of credit and other financial guarantees
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Standby letters of credit and other financial guarantees, investment grade	61,972		66,856
Standby letters of credit and other financial guarantees, non-investment grade	23,452		23,018
Total lending-related commitments	85,424		89,874
Allowance for lending-related commitments	277		234
Standby letters of credit and other financial guarantees, collateral held	37,595		39,726
Other letters of credit
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Standby letters of credit and other financial guarantees, investment grade	3,534		3,476
Standby letters of credit and other financial guarantees, non-investment grade	654		855
Total lending-related commitments	4,188		4,331
Allowance for lending-related commitments	1		1
Other letters of credit, collateral held	1,275		1,509
Derivatives qualifying as guarantees
Standby letters of credit and other financial guarantees and other letters of credit [Abstract]
Guarantor obligations, current carrying value	103		80
Derivatives qualifying as guarantees
Other guarantees and commitments, contractual amount	51,476		53,589
Derivative, notional amount	28,100		27,500
Derivatives maximum exposure to loss	3,000		2,900
Derivative qualifying as guarantees payables	129		102
Derivative qualifying as guarantees receivables	$ 26		$ 22