Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Available-for-sale Securities, Less than 12 Months, Fair Value	$ 1,244,265	$ 1,926,875
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	11,013	39,046
Available-for-sale Securities, 12 Months or Longer, Fair Value	1,251,162	184,632
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	30,803	4,989
Available-for-sale Securities, Fair Value	2,495,427	2,111,507
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	41,816	44,035
US Treasury and Government [Member]
Investment Holdings [Line Items]
Available-for-sale Securities, Less than 12 Months, Fair Value	39,699
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	323
Available-for-sale Securities, 12 Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Available-for-sale Securities, Fair Value	39,699
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	323
Obligations Of States And Political Subdivisions
Investment Holdings [Line Items]
Available-for-sale Securities, Less than 12 Months, Fair Value	20,566	71,571
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	322	3,065
Available-for-sale Securities, 12 Months or Longer, Fair Value	24,798	1,828
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	780	472
Available-for-sale Securities, Fair Value	45,364	73,399
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	1,102	3,537
Residential Mortgage-Backed Securities And Collateralized Mortgage Obligations
Investment Holdings [Line Items]
Available-for-sale Securities, Less than 12 Months, Fair Value	1,184,000	1,855,304
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	10,368	35,981
Available-for-sale Securities, 12 Months or Longer, Fair Value	1,226,364	182,804
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	30,023	4,517
Available-for-sale Securities, Fair Value	2,410,364	2,038,108
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 40,391	$ 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
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

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+ 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

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