Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investment [Line Items]
Less than 12 months, Fair Value	$ 1,732,242	$ 2,125,723
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	11,113	5,488
12 months or longer, Fair Value	789,751	1,137,135
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	18,805	29,896
Total, Fair Value	2,521,993	3,262,858
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	29,918	35,384
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	158,390	90,261
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,701	818
12 months or longer, Fair Value	31,479	32,077
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,532	4,206
Total, Fair Value	189,869	122,338
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	6,233	5,024
Government-Sponsored Enterprise Obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	11,419	224,808
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	57	922
12 months or longer, Fair Value	110,123	224,779
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,692	7,118
Total, Fair Value	121,542	449,587
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	2,749	8,040
State And Municipal Obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	120,098	172,980
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	703	646
12 months or longer, Fair Value	110,550	215,702
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5,790	7,708
Total, Fair Value	230,648	388,682
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	6,493	8,354
Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	64,863	55,128
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	259	429
12 months or longer, Fair Value	305,767	381,617
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,253	5,163
Total, Fair Value	370,630	436,745
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	2,512	5,592
Non-Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	199,875	141,655
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	361	609
12 months or longer, Fair Value	53,765	43,659
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	287	619
Total, Fair Value	253,640	185,314
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	648	1,228
Asset-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	998,031	1,424,457
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5,542	2,009
12 months or longer, Fair Value	152,502	159,098
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,302	3,094
Total, Fair Value	1,150,533	1,583,555
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	7,844	5,103
Total Mortgage And Asset-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	1,262,769	1,621,240
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6,162	3,047
12 months or longer, Fair Value	512,034	584,374
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,842	8,876
Total, Fair Value	1,774,803	2,205,614
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	11,004	11,923
Debt Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	179,566	16,434
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,490	55
12 months or longer, Fair Value	25,565	80,203
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	949	1,988
Total, Fair Value	205,131	96,637
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 3,439	$ 2,043