Loans - Schedule of Additional Information on Nonaccrual Loans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Receivables [Abstract]
Interest income that would have been recorded if the nonaccrual receivable had been current in accordance with contractual terms during the period	$ 13	$ 18	$ 27	$ 38
Interest income that was recorded on nonaccrual loans and included in interest income during the period	$ 6	$ 2	$ 15	$ 13