Acquired and Covered Loans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Certain Loans Acquired in Transfer Accounted for as Debt Securities Accretable Yield Movement Schedule [Line Items]
Non-residential mortgage loans with expired loss share agreements	$ 10.4	$ 12.7
Outstanding balance of PCI loans	175.2	210.7
Renewed non-purchased credit impaired loans	458.0	366.0
Acquired and Covered Receivables
Certain Loans Acquired in Transfer Accounted for as Debt Securities Accretable Yield Movement Schedule [Line Items]
Accretion on acquired loans	$ 19.5	$ 33.9	$ 14.6