Deposits - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Banking and Thrift [Abstract]
Weighted-average interest rate on certificates of deposit (as a percent)	1.01%	0.96%
Aggregate amount of time deposits in denominations of 100,000	$ 481.1	$ 508.6
Aggregate amount of time deposits in denominations of 250,000	102.1	87.4
Brokered deposits	$ 412.7	$ 234.4