Acquisitions - Schedule of Acquired Loans not Deemed to Have Credit Impairment (Details) - USD ($) $ in Millions	Apr. 08, 2019	Aug. 16, 2018
Idaho Independent Bank
Business Acquisition [Line Items]
Contractually required principal and interest payments	$ 398.7
Contractual cash flows not expected to be collected	15.2
Fair value at acquisition	$ 321.5
Inland Northwest Bank
Business Acquisition [Line Items]
Contractually required principal and interest payments		$ 894.8
Contractual cash flows not expected to be collected		26.1
Fair value at acquisition		$ 693.2