Employee Benefit Plans Stock-Based Compensation Expense Recognized in Noninterest Expense (Additional Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Performance Stock Units, Cash Distributions	$ 1	$ 1	$ 75	$ 77