Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Investment [Line Items]
Amortized Cost	$ 9,212,096	$ 9,691,414
Fair Value	9,438,871	9,777,004
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Amortized Cost	738,658	729,846
Fair Value	755,649	727,076
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	59,068
Fair Value	60,028
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	500,823
Fair Value	514,620
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	106,427
Fair Value	110,802
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	72,340
Fair Value	70,199
Government-Sponsored Enterprise Obligations [Member]
Investment [Line Items]
Amortized Cost	445,648	794,912
Fair Value	451,242	793,023
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	11,589
Fair Value	11,627
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	419,071
Fair Value	424,410
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	14,988
Fair Value	15,205
State And Municipal Obligations [Member]
Investment [Line Items]
Amortized Cost	1,776,857	1,706,635
Fair Value	1,836,001	1,741,957
State And Municipal Obligations [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	153,968
Fair Value	155,078
State And Municipal Obligations [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	626,147
Fair Value	641,498
State And Municipal Obligations [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	941,494
Fair Value	983,236
State And Municipal Obligations [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	55,248
Fair Value	56,189
Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	2,590,902	2,579,031
Fair Value	2,663,677	2,618,281
Non-Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	922,302	879,186
Fair Value	937,208	879,963
Asset-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	2,403,019	2,660,201
Fair Value	2,409,324	2,644,381
Total Mortgage And Asset-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	5,916,223	6,118,418
Fair Value	6,010,209	6,142,625
Other Debt Securities [Member]
Investment [Line Items]
Amortized Cost	329,032	335,925
Fair Value	338,812	331,320
Other Debt Securities [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	5,997
Fair Value	6,025
Other Debt Securities [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	97,136
Fair Value	98,939
Other Debt Securities [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	214,311
Fair Value	222,376
Other Debt Securities [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	11,588
Fair Value	11,472
Equity Securities [Member]
Investment [Line Items]
Amortized Cost	5,678	5,678
Fair Value	$ 46,958	$ 41,003