Available-For-Sale And Held-To-Maturity Securities (Schedule Of Gross Unrealized Losses And The Estimated Fair Value By Length Of Time In A Loss Position) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	$ (3,346)
Available-for-sale Securities, Estimated fair value, Less than 12 months	395,637
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(9,808)
Available-for-sale Securities, Estimated fair value, 12 months or more	461,141
Available-for-sale Securities, Gross unrealized losses, Total	(13,154)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	856,778
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(5,790)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	620,211
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(8,636)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	264,225
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(14,426)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	884,436
U.S. Government Agency Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(19)
Available-for-sale Securities, Estimated fair value, Less than 12 months	4,686
Available-for-sale Securities, Gross unrealized losses, Total	(19)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	4,686
State And Municipal Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(11)
Available-for-sale Securities, Estimated fair value, Less than 12 months	3,054
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(3,316)
Available-for-sale Securities, Estimated fair value, 12 months or more	68,907
Available-for-sale Securities, Gross unrealized losses, Total	(3,327)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	71,961
Corporate Fixed Income Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(820)
Available-for-sale Securities, Estimated fair value, Less than 12 months	213,865
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(1,822)
Available-for-sale Securities, Estimated fair value, 12 months or more	171,610
Available-for-sale Securities, Gross unrealized losses, Total	(2,642)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	385,475
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(41)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	9,965
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(41)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	9,965
Asset-Backed Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(1,554)
Available-for-sale Securities, Estimated fair value, Less than 12 months	22,457
Available-for-sale Securities, Gross unrealized losses, Total	(1,554)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	22,457
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(30)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	35,198
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(1,786)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	42,920
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(1,816)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	78,118
Mortgage Backed Securities [Member] | Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(942)
Available-for-sale Securities, Estimated fair value, Less than 12 months	151,575
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(1,527)
Available-for-sale Securities, Estimated fair value, 12 months or more	147,738
Available-for-sale Securities, Gross unrealized losses, Total	(2,469)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	299,313
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(5,719)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	575,048
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(6,850)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	221,305
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(12,569)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	796,353
Mortgage Backed Securities [Member] | Commercial [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(3,143)
Available-for-sale Securities, Estimated fair value, 12 months or more	71,293
Available-for-sale Securities, Gross unrealized losses, Total	(3,143)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	71,293
Mortgage Backed Securities [Member] | Non-Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Estimated fair value, 12 months or more	1,593
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 1,593