Correction of Prior Period Amounts (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other assets	$ 9,620	$ 9,410
Other liabilities	2,048	2,143
Retained earnings	9,524	10,936
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	16,580	18,355	$ 17,386	$ 16,593
Noncontrolling interests	72	100
Noncontrolling Interests
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	72	100	153	215
Retained Earnings
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 9,524	$ 10,936	$ 10,101	$ 9,116