Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Investment [Line Items]
Less than 12 months, Fair Value	$ 565,317	$ 4,352,838
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	7,140	31,844
12 months or longer, Fair Value	312,122	767,349
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	7,105	20,776
Total, Fair Value	877,439	5,120,187
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	14,245	52,620
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	0	491,998
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	3,098
12 months or longer, Fair Value	33,379	31,012
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,263	4,723
Total, Fair Value	33,379	523,010
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	2,263	7,821
Government-Sponsored Enterprise Obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	0	157,830
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	1,975
12 months or longer, Fair Value	0	110,250
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	2,571
Total, Fair Value	0	268,080
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	0	4,546
State And Municipal Obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	17,375	66,998
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	334	544
12 months or longer, Fair Value	9,478	31,120
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	358	1,195
Total, Fair Value	26,853	98,118
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	692	1,739
Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	14,257	530,035
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	22	2,989
12 months or longer, Fair Value	2,611	291,902
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	6	5,617
Total, Fair Value	16,868	821,937
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	28	8,606
Non-Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	3,790	653,603
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2	7,059
12 months or longer, Fair Value	57,411	54,536
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	102	760
Total, Fair Value	61,201	708,139
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	104	7,819
Asset-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	529,895	2,207,922
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6,782	12,492
12 months or longer, Fair Value	189,558	223,311
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,002	4,615
Total, Fair Value	719,453	2,431,233
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	10,784	17,107
Total Mortgage And Asset-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	547,942	3,391,560
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6,806	22,540
12 months or longer, Fair Value	249,580	569,749
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,110	10,992
Total, Fair Value	797,522	3,961,309
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	10,916	33,532
Debt Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	0	244,452
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	3,687
12 months or longer, Fair Value	19,685	25,218
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	374	1,295
Total, Fair Value	19,685	269,670
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 374	$ 4,982