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	12 Months Ended
	Dec. 31, 2015 USD ($)
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	$ (7,455)
Available-for-sale Securities, Estimated fair value, Less than 12 months	1,147,536
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(5,843)
Available-for-sale Securities, Estimated fair value, 12 months or more	185,366
Available-for-sale Securities, Gross unrealized losses, Total	(13,298)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	1,332,902
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(4,158)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	735,650
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(3,497)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	111,317
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(7,655)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	846,967
U S Government Corporations And Agencies Securities
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(3)
Available-for-sale Securities, Estimated fair value, Less than 12 months	1,449
Available-for-sale Securities, Gross unrealized losses, Total	(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	1,449
U S States And Political Subdivisions
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(415)
Available-for-sale Securities, Estimated fair value, Less than 12 months	26,357
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(1,399)
Available-for-sale Securities, Estimated fair value, 12 months or more	38,231
Available-for-sale Securities, Gross unrealized losses, Total	(1,814)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	64,588
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	(2,352)
Available-for-sale Securities, Estimated fair value, Less than 12 months	239,614
Available-for-sale Securities, Gross unrealized losses, Total	(2,352)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	239,614
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(396)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	39,748
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(396)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	39,748
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	(3,519)
Available-for-sale Securities, Estimated fair value, Less than 12 months	600,224
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(3,905)
Available-for-sale Securities, Estimated fair value, 12 months or more	136,257
Available-for-sale Securities, Gross unrealized losses, Total	(7,424)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	736,481
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(1,080)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	258,098
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(3,059)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	68,499
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(4,139)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	326,597
Mortgage Backed Securities | Agency Securities
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(1,165)
Available-for-sale Securities, Estimated fair value, Less than 12 months	279,762
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(376)
Available-for-sale Securities, Estimated fair value, 12 months or more	8,516
Available-for-sale Securities, Gross unrealized losses, Total	(1,541)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	288,278
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(3,078)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	477,552
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(27)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,156
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(3,105)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	479,708
Mortgage Backed Securities | Commercial Mortgage Backed Securities
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(1)
Available-for-sale Securities, Estimated fair value, Less than 12 months	130
Available-for-sale Securities, Gross unrealized losses, Total	(1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	130
Mortgage Backed Securities | 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	(163)
Available-for-sale Securities, Estimated fair value, 12 months or more	2,362
Available-for-sale Securities, Gross unrealized losses, Total	(163)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	2,362
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(15)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	914
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(15)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 914