Investments (Securities Gains (Losses)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments [Abstract]
Gross gains on retirement/sales of investment securities available for sale	$ 60,932	$ 8,993	$ 353
Gross losses on sales of investment securities available for sale	(679)	(1,878)	(2)
Realized gains on investment securities available for sale, net	$ 60,253	$ 7,115	$ 351