Investment Securities (Gains and Losses on Sales) (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Carrying value of investment securities which were pledged to secure deposits of gov't entities and repos	$ 2,600,000	$ 2,300,000	$ 2,400,000
Gain on Sale of Investments	7,810	0	12,467
Loss on Sale of Investments	11,796	3,938	2,037
Gain (Loss) on Sale of Investments	$ (3,986)	$ (3,938)	$ 10,430