Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Investment [Line Items]
Amortized Cost	$ 9,386,302		$ 8,874,540
Fair Value	9,523,560		8,915,680
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Amortized Cost	497,336		498,226
Fair Value	501,407		505,696
Weighted Average Yield	1.14%	[1]
U.S. Government And Federal Agency Obligations [Member] | Maturity Within 1 Year [Member]
Investment [Line Items]
Amortized Cost	104,791
Fair Value	104,782
Weighted Average Yield	1.56%	[1]
U.S. Government And Federal Agency Obligations [Member] | Maturity After 1 But Within 5 Years [Member]
Investment [Line Items]
Amortized Cost	198,166
Fair Value	204,838
Weighted Average Yield	1.57%	[1]
U.S. Government And Federal Agency Obligations [Member] | Maturity After 5 But Within 10 Years [Member]
Investment [Line Items]
Amortized Cost	141,179
Fair Value	142,575
Weighted Average Yield	0.64%	[1]
U.S. Government And Federal Agency Obligations [Member] | Maturity After 10 Years [Member]
Investment [Line Items]
Amortized Cost	53,200
Fair Value	49,212
Weighted Average Yield	0.01%	[1]
Government-sponsored enterprise obligations [Member]
Investment [Line Items]
Amortized Cost	968,574		766,802
Fair Value	963,127		741,766
Weighted Average Yield	1.82%
Government-sponsored enterprise obligations [Member] | Maturity Within 1 Year [Member]
Investment [Line Items]
Amortized Cost	53,022
Fair Value	53,567
Weighted Average Yield	1.82%
Government-sponsored enterprise obligations [Member] | Maturity After 1 But Within 5 Years [Member]
Investment [Line Items]
Amortized Cost	425,884
Fair Value	426,591
Weighted Average Yield	1.54%
Government-sponsored enterprise obligations [Member] | Maturity After 5 But Within 10 Years [Member]
Investment [Line Items]
Amortized Cost	423,873
Fair Value	417,331
Weighted Average Yield	2.03%
Government-sponsored enterprise obligations [Member] | Maturity After 10 Years [Member]
Investment [Line Items]
Amortized Cost	65,795
Fair Value	65,638
Weighted Average Yield	2.22%
State and municipal obligations [Member]
Investment [Line Items]
Amortized Cost	1,789,215		1,624,195
Fair Value	1,813,201		1,619,171
Weighted Average Yield	2.35%
State and municipal obligations [Member] | Maturity Within 1 Year [Member]
Investment [Line Items]
Amortized Cost	178,463
Fair Value	180,247
Weighted Average Yield	2.87%
State and municipal obligations [Member] | Maturity After 1 But Within 5 Years [Member]
Investment [Line Items]
Amortized Cost	688,284
Fair Value	708,764
Weighted Average Yield	2.47%
State and municipal obligations [Member] | Maturity After 5 But Within 10 Years [Member]
Investment [Line Items]
Amortized Cost	808,478
Fair Value	813,479
Weighted Average Yield	2.23%
State and municipal obligations [Member] | Maturity After 10 Years [Member]
Investment [Line Items]
Amortized Cost	113,990
Fair Value	110,711
Weighted Average Yield	1.61%
Agency mortgage-backed securities [Member]
Investment [Line Items]
Amortized Cost	2,523,377		2,743,803
Fair Value	2,593,708		2,772,338
Weighted Average Yield	2.69%
Non-agency mortgage-backed securities [Member]
Investment [Line Items]
Amortized Cost	372,911		236,595
Fair Value	382,744		246,983
Weighted Average Yield	3.05%
Asset-backed securities [Member]
Investment [Line Items]
Amortized Cost	3,090,174		2,847,368
Fair Value	3,091,993		2,844,071
Weighted Average Yield	0.87%
Total mortgage and asset-backed securities [Member]
Investment [Line Items]
Amortized Cost	5,986,462		5,827,766
Fair Value	6,068,445		5,863,392
Weighted Average Yield	1.77%
Other debt securities [Member]
Investment [Line Items]
Amortized Cost	140,784		147,581
Fair Value	139,161		141,757
Other debt securities [Member] | Maturity Within 1 Year [Member]
Investment [Line Items]
Amortized Cost	11,248
Fair Value	11,249
Other debt securities [Member] | Maturity After 1 But Within 5 Years [Member]
Investment [Line Items]
Amortized Cost	50,091
Fair Value	50,344
Other debt securities [Member] | Maturity After 5 But Within 10 Years [Member]
Investment [Line Items]
Amortized Cost	79,445
Fair Value	77,568
Equity securities [Member]
Investment [Line Items]
Amortized Cost	3,931		9,970
Fair Value	$ 38,219		$ 43,898

[1] Rate does not reflect inflation adjustment on inflation-protected securities