Investment Securities Available for Sale (Schedule Of Unrealized Loss On Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 3,012,769	$ 1,990,616
Less than 12 Months, Unrealized Losses	60,156	14,491
12 Months or Longer, Fair Value	33,315	585,640
12 Months or Longer, Unrealized Losses	1,381	12,792
Total Fair Value	3,046,084	2,576,256
Total Unrealized Losses	61,537	27,283
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	64,023
Less than 12 Months, Unrealized Losses	644
12 Months or Longer, Fair Value	0
12 Months or Longer, Unrealized Losses	0
Total Fair Value	64,023
Total Unrealized Losses	644
Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	128,121	122,626
Less than 12 Months, Unrealized Losses	1,240	639
12 Months or Longer, Fair Value	3,626	18,435
12 Months or Longer, Unrealized Losses	114	482
Total Fair Value	131,747	141,061
Total Unrealized Losses	1,354	1,121
Mortgage-Backed Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	2,123,181	1,656,194
Less than 12 Months, Unrealized Losses	42,571	12,874
12 Months or Longer, Fair Value	0	489,971
12 Months or Longer, Unrealized Losses	0	9,688
Total Fair Value	2,123,181	2,146,165
Total Unrealized Losses	42,571	22,562
Collateralized Mortgage Obligations Issued by U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	682,492	196,811
Less than 12 Months, Unrealized Losses	15,653	963
12 Months or Longer, Fair Value	24,801	72,366
12 Months or Longer, Unrealized Losses	908	2,262
Total Fair Value	707,293	269,177
Total Unrealized Losses	16,561	3,225
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value		0
Less than 12 Months, Unrealized Losses		0
12 Months or Longer, Fair Value		50
12 Months or Longer, Unrealized Losses		1
Total Fair Value		50
Total Unrealized Losses		1
Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	14,952	14,985
Less than 12 Months, Unrealized Losses	48	15
12 Months or Longer, Fair Value	4,888	4,818
12 Months or Longer, Unrealized Losses	359	359
Total Fair Value	19,840	19,803
Total Unrealized Losses	$ 407	$ 374