Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Investment [Line Items]
Amortized Cost	$ 8,972,472	$ 9,691,414
Fair Value	9,221,346	9,777,004
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Amortized Cost	700,801	729,846
Fair Value	720,919	727,076
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	59,365
Fair Value	59,898
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	499,992
Fair Value	517,665
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	105,802
Fair Value	109,977
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	35,642
Fair Value	33,379
Government-Sponsored Enterprise Obligations [Member]
Investment [Line Items]
Amortized Cost	554,030	794,912
Fair Value	562,177	793,023
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	81,208
Fair Value	81,302
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	452,204
Fair Value	459,978
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	14,988
Fair Value	15,260
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	5,630
Fair Value	5,637
State And Municipal Obligations [Member]
Investment [Line Items]
Amortized Cost	1,764,118	1,706,635
Fair Value	1,833,861	1,741,957
State And Municipal Obligations [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	135,577
Fair Value	136,305
State And Municipal Obligations [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	642,897
Fair Value	662,010
State And Municipal Obligations [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	923,727
Fair Value	971,348
State And Municipal Obligations [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	61,917
Fair Value	64,198
Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	2,509,991	2,579,031
Fair Value	2,589,915	2,618,281
Non-Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	814,917	879,186
Fair Value	831,616	879,963
Asset-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	2,293,845	2,660,201
Fair Value	2,298,725	2,644,381
Total Mortgage And Asset-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	5,618,753	6,118,418
Fair Value	5,720,256	6,142,625
Other Debt Securities [Member]
Investment [Line Items]
Amortized Cost	329,092	335,925
Fair Value	339,264	331,320
Other Debt Securities [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	5,996
Fair Value	6,052
Other Debt Securities [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	88,771
Fair Value	90,755
Other Debt Securities [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	222,737
Fair Value	231,176
Other Debt Securities [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	11,588
Fair Value	11,281
Equity Securities [Member]
Investment [Line Items]
Amortized Cost	5,678	5,678
Fair Value	$ 44,869	$ 41,003