Qualified Affordable Housing (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Investments in qualified affordable housing projects	$ 6.3	$ 9.0
Tax credits to offset amortization expense of investments in affordable housing projects	3.1	3.4	$ 3.7
Noninterest Expense
Schedule of Equity Method Investments [Line Items]
Amortization expense of investments in qualified affordable housing projects	$ 2.7	$ 3.0	$ 3.3