Deposits - Scheduled Maturity of Total Time Deposits (Details) $ in Millions	Dec. 31, 2020 USD ($)
Time Deposits [Line Items]
1 Year or Less	$ 865.6
Over 1 Year to 2 Years	36.1
Over 2 Years to 3 Years	3.1
Over 3 Years to 4 Years	1.2
Over 4 Years to 5 Years	0.3
Over 5 Years	0.5
Total	906.8
U.S. OFFICE
Time Deposits [Line Items]
1 Year or Less	660.2
Over 1 Year to 2 Years	36.1
Over 2 Years to 3 Years	3.1
Over 3 Years to 4 Years	1.2
Over 4 Years to 5 Years	0.3
Over 5 Years	0.5
Total	701.4
NON-U.S. OFFICES
Time Deposits [Line Items]
1 Year or Less	205.4
Over 1 Year to 2 Years	0.0
Over 2 Years to 3 Years	0.0
Over 3 Years to 4 Years	0.0
Over 4 Years to 5 Years	0.0
Over 5 Years	0.0
Total	$ 205.4