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	6 Months Ended
	Jun. 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	$ (7,948)
Available-for-sale Securities, Estimated fair value, Less than 12 months	636,866
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(4,965)
Available-for-sale Securities, Estimated fair value, 12 months or more	195,362
Available-for-sale Securities, Gross unrealized losses, Total	(12,913)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	832,228
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(14,769)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	947,884
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(1,768)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	35,556
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(16,537)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	983,440
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	4,565
Available-for-sale Securities, Gross unrealized losses, Total	(19)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	4,565
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	(261)
Available-for-sale Securities, Estimated fair value, Less than 12 months	9,765
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(3,044)
Available-for-sale Securities, Estimated fair value, 12 months or more	60,113
Available-for-sale Securities, Gross unrealized losses, Total	(3,305)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	69,878
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	(3,579)
Available-for-sale Securities, Estimated fair value, Less than 12 months	396,324
Available-for-sale Securities, Gross unrealized losses, Total	(3,579)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	396,324
Asset-Backed Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(312)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	116,997
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(1,751)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	34,391
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(2,063)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	151,388
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	(604)
Available-for-sale Securities, Estimated fair value, Less than 12 months	155,073
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(1,817)
Available-for-sale Securities, Estimated fair value, 12 months or more	133,664
Available-for-sale Securities, Gross unrealized losses, Total	(2,421)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	288,737
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(14,457)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	830,887
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(17)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,165
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(14,474)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	832,052
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, Less than 12 months	(3,485)
Available-for-sale Securities, Estimated fair value, Less than 12 months	71,139
Available-for-sale Securities, Gross unrealized losses, Total	(3,485)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	71,139
Mortgage Backed Securities [Member] | Non-Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(104)
Available-for-sale Securities, Estimated fair value, 12 months or more	1,585
Available-for-sale Securities, Gross unrealized losses, Total	(104)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 1,585