Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Available-for-sale securities, less than 12 months, fair value	$ 1,441,040	$ 1,244,265
Available-for-sale securities, less than 12 months, unrealized losses	29,824	11,013
Available-for-sale securities, 12 months or longer, fair value	1,234,159	1,251,162
Available-for-sale securities, 12 months or longer, unrealized losses	49,151	30,803
Available-for-sale securities, fair value	2,675,199	2,495,427
Available-for-sale securities, unrealized losses	78,975	41,816
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale securities, less than 12 months, fair value	39,518	39,699
Available-for-sale securities, less than 12 months, unrealized losses	499	323
Available-for-sale securities, 12 months or longer, fair value	0	0
Available-for-sale securities, 12 months or longer, unrealized losses	0	0
Available-for-sale securities, fair value	39,518	39,699
Available-for-sale securities, unrealized losses	499	323
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, less than 12 months, fair value	92,400	20,566
Available-for-sale securities, less than 12 months, unrealized losses	2,058	322
Available-for-sale securities, 12 months or longer, fair value	24,496	24,798
Available-for-sale securities, 12 months or longer, unrealized losses	1,541	780
Available-for-sale securities, fair value	116,896	45,364
Available-for-sale securities, unrealized losses	3,599	1,102
Residential mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Available-for-sale securities, less than 12 months, fair value	1,309,122	1,184,000
Available-for-sale securities, less than 12 months, unrealized losses	27,267	10,368
Available-for-sale securities, 12 months or longer, fair value	1,209,663	1,226,364
Available-for-sale securities, 12 months or longer, unrealized losses	47,610	30,023
Available-for-sale securities, fair value	2,518,785	2,410,364
Available-for-sale securities, unrealized losses	$ 74,877	$ 40,391

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
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

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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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