Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Available-for-sale securities, less than 12 months, fair value	$ 1,182,459	$ 1,926,875
Available-for-sale securities, less than 12 months, unrealized losses	10,939	39,046
Available-for-sale securities, 12 months or longer, fair value	692,552	184,632
Available-for-sale securities, 12 months or longer, unrealized losses	13,639	4,989
Available-for-sale securities, fair value	1,875,011	2,111,507
Available-for-sale securities, unrealized losses	24,578	44,035
Obligations Of States And Political Subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, less than 12 months, fair value	13,108	71,571
Available-for-sale securities, less than 12 months, unrealized losses	147	3,065
Available-for-sale securities, 12 months or longer, fair value	25,256	1,828
Available-for-sale securities, 12 months or longer, unrealized losses	742	472
Available-for-sale securities, fair value	38,364	73,399
Available-for-sale securities, unrealized losses	889	3,537
Residential Mortgage-Backed Securities And Collateralized Mortgage Obligations
Investment Holdings [Line Items]
Available-for-sale securities, less than 12 months, fair value	1,169,351	1,855,304
Available-for-sale securities, less than 12 months, unrealized losses	10,792	35,981
Available-for-sale securities, 12 months or longer, fair value	667,296	182,804
Available-for-sale securities, 12 months or longer, unrealized losses	12,897	4,517
Available-for-sale securities, fair value	1,836,647	2,038,108
Available-for-sale securities, unrealized losses	$ 23,689	$ 40,498

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Publisher FASB
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