Securities (Narrative) (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) security	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) security
Unrealized Loss
Number of available-for-sale debt securities in an unrealized loss position | security	291		104
Available-for-sale debt securities, in gross unrealized loss position	$ 0		$ 0
Available-for-sale, allowance for credit loss	0		$ 0
Provision for credit losses	0	$ 73,870,000
AFS debt securities
Unrealized Loss
Provision for credit losses	$ 0	$ 0
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities
Unrealized Loss
Number of available-for-sale debt securities in an unrealized loss position | security	112		46
U.S. government-sponsored enterprises debt securities
Unrealized Loss
Number of available-for-sale debt securities in an unrealized loss position | security	41
Corporate debt securities
Unrealized Loss
Number of available-for-sale debt securities in an unrealized loss position | security	26		17
AFS debt securities
Unrealized Loss
AFS debt securities, accrued interest	$ 22,900,000		$ 22,300,000