Goodwill And Other Intangible Assets (Schedule Of Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 1,014,129	$ 1,014,129
Impairment losses	0	0
Goodwill, Ending Balance	1,014,129	1,014,129
Zions Bank [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	19,514	19,514
Impairment losses	0	0
Goodwill, Ending Balance	19,514	19,514
California Bank And Trust [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	379,024	379,024
Impairment losses	0	0
Goodwill, Ending Balance	379,024	379,024
Amegy [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	615,591	615,591
Impairment losses	0	0
Goodwill, Ending Balance	$ 615,591	$ 615,591