Premises and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 34	$ 32	$ 32
Rental expense under leases	10	$ 6	$ 8
Lease Breakage Cost [Member]
Property, Plant and Equipment [Line Items]
Variable Lease, Cost	$ 5