Premises and Equipment (Details Textuals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 32	$ 32	$ 33
Rental expense under leases	6	8	$ 13
Milwaukee Center
Property, Plant and Equipment [Line Items]
Leasing income	$ 5	$ 4