Investments in Affordable Housing Limit Partnerships (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Investments in affordable housing limited partnerships, funding installment period	3 years
Other non-interest expenses
Schedule of Equity Method Investments [Line Items]
Expense related to investments in affordable housing limited partnerships	$ 1.1	$ 1.5	$ 1.5
Income tax expense
Schedule of Equity Method Investments [Line Items]
Affordable housing tax credits and other tax benefits	1.4	2.2	$ 2.2
Other assets
Schedule of Equity Method Investments [Line Items]
Investment in affordable housing limited partnerships	17.2	18.3
Other liabilities
Schedule of Equity Method Investments [Line Items]
Funding obligation related to investments in affordable housing limited partnerships	$ 12.9	$ 15.0