Common Stock - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 28, 2018
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	9,000,000,000.0	9,000,000,000
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Stock repurchase program, shares authorized (in shares)				$ 20,700,000,000
Remaining authorized repurchase amount	$ 10,400,000,000
Warrant
Class of Stock [Line Items]
Total warrants repurchased (in shares)	0	0	0
Warrant | JPMorgan Chase & Co.
Class of Stock [Line Items]
Warrants outstanding (in shares)	0	15,000,000.0	24,900,000
Common stock
Class of Stock [Line Items]
Common stock capital shares reserved for future issuance (shares)	85,000,000