Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Amortized Cost	$ 9,012,095	$ 7,164,763
Fair Value	9,224,702	7,294,303
U.S. Government And Federal Agency Obligations [Member]
Amortized Cost	328,530	434,878
Fair Value	364,665	455,537
Weighted Average Yield	1.65%
U.S. Government And Federal Agency Obligations [Member] | Within 1 Year [Member]
Amortized Cost	7,753
Fair Value	8,010
Weighted Average Yield	5.42%
U.S. Government And Federal Agency Obligations [Member] | After 1 But Within 5 Years [Member]
Amortized Cost	158,173
Fair Value	173,356
Weighted Average Yield	1.64%
U.S. Government And Federal Agency Obligations [Member] | After 5 But Within 10 Years [Member]
Amortized Cost	162,604
Fair Value	183,299
Weighted Average Yield	1.49%
Government-Sponsored Enterprise Obligations [Member]
Amortized Cost	311,529	200,061
Fair Value	315,698	201,895
Weighted Average Yield	1.99%
Government-Sponsored Enterprise Obligations [Member] | Within 1 Year [Member]
Amortized Cost	56,255
Fair Value	56,683
Weighted Average Yield	2.62%
Government-Sponsored Enterprise Obligations [Member] | After 1 But Within 5 Years [Member]
Amortized Cost	130,587
Fair Value	133,969
Weighted Average Yield	1.85%
Government-Sponsored Enterprise Obligations [Member] | After 5 But Within 10 Years [Member]
Amortized Cost	37,274
Fair Value	37,435
Weighted Average Yield	1.66%
Government-Sponsored Enterprise Obligations [Member] | After 10 Years [Member]
Amortized Cost	87,413
Fair Value	87,611
Weighted Average Yield	1.94%
State And Municipal Obligations [Member]
Amortized Cost	1,220,840	1,117,020
Fair Value	1,245,284	1,119,485
Weighted Average Yield	2.79%
State And Municipal Obligations [Member] | Within 1 Year [Member]
Amortized Cost	104,945
Fair Value	106,281
Weighted Average Yield	3.44%
State And Municipal Obligations [Member] | After 1 But Within 5 Years [Member]
Amortized Cost	513,033
Fair Value	529,531
Weighted Average Yield	2.75%
State And Municipal Obligations [Member] | After 5 But Within 10 Years [Member]
Amortized Cost	375,836
Fair Value	390,333
Weighted Average Yield	3.00%
State And Municipal Obligations [Member] | After 10 Years [Member]
Amortized Cost	227,026
Fair Value	219,139
Weighted Average Yield	2.27%
Mortgage And Asset-Backed Securities [Member] | Agency Mortgage-Backed Securities [Member]
Amortized Cost	3,989,464
Fair Value	4,106,059
Weighted Average Yield	3.07%
Mortgage And Asset-Backed Securities [Member] | Non-Agency Mortgage-Backed Securities [Member]
Amortized Cost	315,752
Fair Value	316,902
Weighted Average Yield	6.10%
Mortgage And Asset-Backed Securities [Member] | Asset-Backed Securities [Member]
Amortized Cost	2,692,436
Fair Value	2,693,143
Weighted Average Yield	1.12%
Other Debt Securities [Member]
Amortized Cost	135,190	165,883
Fair Value	141,260	176,964
Other Debt Securities [Member] | Within 1 Year [Member]
Amortized Cost	63,547
Fair Value	64,266
Other Debt Securities [Member] | After 1 But Within 5 Years [Member]
Amortized Cost	71,643
Fair Value	76,994
Equity Securities [Member]
Amortized Cost	18,354	7,569
Fair Value	41,691	39,173
Agency Mortgage-Backed Securities [Member]
Amortized Cost	3,989,464	2,437,123
Fair Value	4,106,059	2,491,199
Non-Agency Mortgage-Backed Securities [Member]
Amortized Cost	315,752	459,363
Fair Value	316,902	455,790
Total Mortgage And Asset-Backed Securities [Member]
Amortized Cost	6,997,652	5,239,352
Fair Value	$ 7,116,104	$ 5,301,249
Weighted Average Yield	2.46%