Restrictions (Restrictions on Cash, Dividends and Other Capital Actions- Additional Information) (Detail) - USD ($)	3 Months Ended							12 Months Ended
	Sep. 30, 2017	Dec. 31, 2015	Jun. 30, 2014	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2011
Restricted Cash and Cash Equivalents Items
Banking Subsidiary Reserve Requirement								$ 1,500,000,000	$ 1,600,000,000
Dividend Received From Nonbank Companies And Related Subsidiaries								2,300,000,000	1,900,000,000
BHC stress test threshold											$ 50,000,000,000
Increase to quarterly common stock dividend	$ 0.16
Gain on sale of Vantiv, Inc. shares								1,037,000,000	0	$ 331,000,000
Vantiv Holding, LLC
Restricted Cash and Cash Equivalents Items
Gain on sale of Vantiv, Inc. shares	$ 1,037,000,000	$ 331,000,000	$ 125,000,000	$ 85,000,000	$ 242,000,000	$ 157,000,000	$ 115,000,000	1,000,000,000
Yearly Average
Restricted Cash and Cash Equivalents Items
Banking Subsidiary Reserve Requirement								$ 1,400,000,000	$ 1,600,000,000
CCAR authorization
Restricted Cash and Cash Equivalents Items
Common stock dividends restrictions								The increase in the quarterly common stock dividend to $0.16 from $0.14 beginning in the third quarter of 2017 and to $0.18 beginning in the second quarter of 2018
Stock Repurchase Authorization Amount								$ 1,161,000,000
CCAR authorization | Repurchases related to share issuances under employee benefit plans
Restricted Cash and Cash Equivalents Items
Stock Repurchase Authorization Amount								88,000,000
CCAR authorization | Repurchases related to previously-recognized TRA transaction after-tax gains
Restricted Cash and Cash Equivalents Items
Stock Repurchase Authorization Amount								$ 48,000,000