Investment Securities Investment Securities (Details 1) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Proceeds from sales of securities available-for-sale		$ 1,584,860	$ 571,800	$ 759,300
Available-for-sale Securities, Gross Realized Gains		29,584	9,225	3,295
Available-for-sale Securities, Gross Realized Losses		4,139	1,049	3,836
Realized Investment Gains (Losses)		25,445	8,176	(541)
Available-for-sale Securities
Proceeds from sales of securities available-for-sale	[1]	$ 1,559,415	$ 563,625	$ 759,841

[1] (1) The securities sold in 2017 included $404.5 million of the $447.0 million of securities obtained in the CUB acquisition that were sold for no gain or loss as they were marked to fair value at the time of acquisition.