v3.10.0.1
Parent Company (Condensed Cash Flow Statements) (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Cash flows from operating activities                      
Net income $ 1,558 $ 2,154 $ 2,467 $ 2,704 $ 663 $ 1,791 $ 1,791 $ 1,971 $ 8,883 $ 6,216 $ 6,123
Adjustments to reconcile net income to net cash provided by (used for) operating activities:                      
Other operating activities                 199 153 (102)
Net cash provided by (used for) operating activities                 7,305 (4,505) 5,383
Cash flows from investing activities                      
Purchases of investment securities                 (27,800) (23,962) (50,911)
Proceeds from sales of investment securities                 3,208 18,131 33,716
Proceeds from paydowns and maturities                 12,668 7,445 8,367
Net cash provided by (used for) investing activities                 (22,881) (12,391) (19,508)
Cash flows from financing activities                      
Issuance of preferred stock, net of issuance costs                 0 994 0
Issuance of Borrowings                 40,059 55,416 43,626
Payments for Borrowings                 (34,781) (35,825) (31,596)
Repurchases of common stock and employee tax withholdings                 (5,566) (4,292) (3,933)
Cash dividends                 (2,375) (2,085) (1,746)
Other financing activities                 (160) 136 (54)
Net cash provided by (used for) financing activities                 24,205 16,261 7,363
Effect of exchange rate changes on cash and cash equivalents                 (1,828) 3,670 (1,430)
Net increase (decrease) in cash and cash equivalents                 6,801 3,035 (8,192)
Cash and cash equivalents, at beginning of period       80,395       77,360 80,395 77,360 85,552
Cash and cash equivalents, at end of period 87,196       80,395       87,196 80,395 77,360
Cash and cash equivalents:                      
Cash and due from banks 30,541       24,816       30,541 24,816 22,017
Restricted cash 35,356       34,231       35,356 34,231 33,979
Supplemental Disclosure of Cash Flow Information                      
Cash payments for interest                 9,977 5,377 2,834
Cash payments for income taxes, net of refunds                 1,377 1,390 831
Parent Company                      
Cash flows from operating activities                      
Net income                 8,748 6,111 5,979
Adjustments to reconcile net income to net cash provided by (used for) operating activities:                      
Undistributed gain of subsidiaries                 (3,617) (4,070) (4,168)
Other operating activities                 964 1,087 1,367
Changes in assets and liabilities                 (7,231) 619 (151)
Net cash provided by (used for) operating activities                 (1,136) 3,747 3,027
Cash flows from investing activities                      
Purchases of investment securities                 (8,155) (5,263) 0
Proceeds from sales of investment securities                 1,252 3,620 0
Proceeds from paydowns and maturities                 3,729 1,038 0
Securities purchased under agreement to resell with affiliate                 13,057 19,314 (10,846)
Securities sold under agreements to repurchase with affiliates                 (8,753) 8,753 0
Advances to and investments in subsidiaries                 11,841 (35,686) (141)
Net cash provided by (used for) investing activities                 12,971 (8,224) (10,987)
Cash flows from financing activities                      
Issuance of preferred stock, net of issuance costs                 0 994 0
Issuance of Borrowings                 14,918 36,833 32,795
Payments for Borrowings                 (21,418) (24,668) (24,793)
Repurchases of common stock and employee tax withholdings                 (5,566) (4,292) (3,933)
Cash dividends                 (2,375) (2,085) (1,746)
Proceeds from (payment of) payables to subsidiaries                 2,122 1,861 (2,361)
Other financing activities                 0 26 66
Net cash provided by (used for) financing activities                 (12,319) 8,669 28
Effect of exchange rate changes on cash and cash equivalents                 (166) 221 (250)
Net increase (decrease) in cash and cash equivalents                 (650) 4,413 (8,182)
Cash and cash equivalents, at beginning of period       $ 8,132       $ 3,719 8,132 3,719 11,901
Cash and cash equivalents, at end of period 7,482       8,132       7,482 8,132 3,719
Cash and cash equivalents:                      
Cash and due from banks 6       11       6 11 116
Deposits with banking subsidiaries 7,476       8,120       7,476 8,120 3,600
Restricted cash $ 0       $ 1       0 1 3
Supplemental Disclosure of Cash Flow Information                      
Cash payments for interest                 4,798 3,570 3,650
Cash payments for income taxes, net of refunds                 $ 437 $ 201 $ 201