Investment Securities (Proceeds From Sales Of Securities And Components Of Investment Securities Gains And Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Proceeds from sales of available for sale securities	$ 790,152	$ 2,049	$ 675,870
Proceeds from sales of non-marketable securities	2,228	22,331	13,161
Total proceeds	792,380	24,380	689,031
Investment securities gains (losses), net	25,051	(53)	6,320
Available-for-sale Securities [Member]
Investment [Line Items]
Gains realized on sales	10,656	109	2,925
Loss realized on sales	(10,297)	0	0
Loss Realized on Called Bond	(254)	0	0
Gain realized on donation	31,074	0	0
Other-than-temporary impairment recognized on debt securities	(385)	(270)	(483)
Non-Marketable [Member]
Investment [Line Items]
Gains realized on sales	970	4,349	2,516
Losses realized on sales	(880)	(502)	(40)
Fair value adjustments, net	$ (5,833)	$ (3,739)	$ 1,402