Assets Purchased under Resale Agreements and Sold under Repurchase Agreements (Resale Agreements) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Offsetting Assets [Line Items]
Gross resale agreements	$ 1,330.0	$ 1,160.0
Loans purchased under agreements to resell	$ 1,020.0	$ 300.0
Loans Purchased Under Resale Agreements
Offsetting Assets [Line Items]
Weighted average yield (as a percent)	1.53%	2.27%
Securities Purchased Under Resale Agreements
Offsetting Assets [Line Items]
Weighted average yield (as a percent)	1.53%	1.94%	2.66%