Fair Value Disclosures (Financial Instruments Not Measured at Fair Value) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Financial Assets
Cash and due from banks	$ 29,073	$ 24,816	$ 22,081
Interest bearing deposits with banks	22,980	21,348	20,773
Restricted cash	35,291	34,231	$ 36,027
Securities purchased under agreements to resell	80,246	84,258
Securities borrowed	135,835	124,010
Customer and other receivables	66,835	56,187
Loans	95,124	92,953
Financial Liabilities
Deposits	160,424	159,436
Securities sold under agreements to repurchase	51,575	56,424
Securities loaned	13,556	13,592
Other secured financings	10,275	11,271
Customer and other payables	194,924	191,510
Borrowings	194,964	192,582
Additional Disclosures
Commitment amount	117,582	100,151
Carrying Value
Financial Assets
Cash and due from banks	29,073	24,816
Interest bearing deposits with banks	22,980	21,348
Restricted cash	35,291	34,231
Investment securities - HTM securities	23,892	23,599
Securities purchased under agreements to resell	80,246	84,258
Securities borrowed	135,835	124,010
Customer and other receivables	61,017	51,269
Loans	109,135	104,126
Other assets	438	433
Financial Liabilities
Deposits	160,182	159,232
Securities sold under agreements to repurchase	50,783	55,624
Securities loaned	13,556	13,592
Other secured financings	6,852	7,408
Customer and other payables	191,332	188,464
Borrowings	147,431	145,670
Fair Value
Financial Assets
Cash and due from banks	29,073	24,816
Interest bearing deposits with banks	22,980	21,348
Restricted cash	35,291	34,231
Investment securities - HTM securities	22,919	23,081
Securities purchased under agreements to resell	80,191	84,217
Securities borrowed	135,781	124,019
Customer and other receivables	60,838	51,143
Loans	108,833	104,218
Other assets	438	433
Financial Liabilities
Deposits	160,172	159,232
Securities sold under agreements to repurchase	50,764	55,619
Securities loaned	13,623	13,592
Other secured financings	6,872	7,418
Customer and other payables	191,332	188,464
Borrowings	151,691	151,722
Additional Disclosures
Commitment amount	828	794
Fair Value | Level 1
Financial Assets
Cash and due from banks	29,073	24,816
Interest bearing deposits with banks	22,980	21,348
Restricted cash	35,291	34,231
Investment securities - HTM securities	11,327	11,119
Securities purchased under agreements to resell	0	0
Securities borrowed	0	0
Customer and other receivables	0	0
Loans	0	0
Other assets	0	0
Financial Liabilities
Deposits	0	0
Securities sold under agreements to repurchase	0	0
Securities loaned	0	0
Other secured financings	0	0
Customer and other payables	0	0
Borrowings	0	0
Fair Value | Level 2
Financial Assets
Cash and due from banks	0	0
Interest bearing deposits with banks	0	0
Restricted cash	0	0
Investment securities - HTM securities	11,270	11,673
Securities purchased under agreements to resell	80,175	78,239
Securities borrowed	135,781	124,018
Customer and other receivables	57,405	47,159
Loans	25,687	21,290
Other assets	438	433
Financial Liabilities
Deposits	160,172	159,232
Securities sold under agreements to repurchase	50,763	51,752
Securities loaned	13,623	13,191
Other secured financings	6,265	5,987
Customer and other payables	191,332	188,464
Borrowings	151,664	151,692
Additional Disclosures
Commitment amount	643	620
Fair Value | Level 3
Financial Assets
Cash and due from banks	0	0
Interest bearing deposits with banks	0	0
Restricted cash	0	0
Investment securities - HTM securities	322	289
Securities purchased under agreements to resell	16	5,978
Securities borrowed	0	1
Customer and other receivables	3,433	3,984
Loans	83,146	82,928
Other assets	0	0
Financial Liabilities
Deposits	0	0
Securities sold under agreements to repurchase	1	3,867
Securities loaned	0	401
Other secured financings	607	1,431
Customer and other payables	0	0
Borrowings	27	30
Additional Disclosures
Commitment amount	$ 185	$ 174