- Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Salaries and employee benefits	$ 2,616	$ 2,495	$ 2,439
Other	$ 409	389	395
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Salaries and employee benefits		2,376	2,355
Other		508	479
Accounting Standards Update 2017-07 | Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Salaries and employee benefits		119	84
Other		$ (119)	$ (84)