Loans - Schedule of Additional Information on Nonaccrual Loans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Interest income that would have been recorded if the nonaccrual receivable had been current in accordance with contractual terms during the period	$ 68	$ 91	$ 85
Interest income that was recorded on nonaccrual loans and included in interest income during the period	$ 24	$ 22	$ 22