Investment Securities (Summary Of Amount Of Gross Unrealized Losses For Debt Securities And Estimated Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	$ 8,395	$ 13,602
Available-for-sale, Less than 12 months - Estimated fair value	878,929	1,326,690
Available-for-sale, 12 months or more - Gross unrealized losses	159,669	129,717
Available-for-sale, 12 months or more - Estimated fair value	1,013,150	699,056
Available-for-sale, Total - Gross unrealized losses	168,064	143,319
Available-for-sale, Total - Estimated fair value	1,892,079	2,025,746
Investment Securities Gross Unrealized Losses Less Than 12 Months	9,117	14,182
Investment Securities Estimated Fair Value Less Than 12 Months	972,132	1,389,574
Investment Securities Gross Unrealized Losses 12 Months or More	159,750	170,303
Investment Securities Estimated Fair Value 12 Months or More	1,016,981	770,245
Investment Securities Gross Unrealized Losses Total	168,867	184,485
Investment Securities Estimated Fair Value Total	1,989,113	2,159,819
Municipal Securities [Member]
Investment [Line Items]
Held-to-maturity, Less than 12 months - Gross unrealized losses	722	527
Held-to-maturity, Less than 12 months - Estimated fair value	93,203	62,762
Held-to-maturity, 12 months or more - Gross unrealized losses	81	277
Held-to-maturity, 12 months or more - Estimated fair value	3,831	14,003
Held-to-maturity, Total - Gross unrealized losses	803	804
Held-to-maturity, Total - Estimated fair value	97,034	76,765
Available-for-sale, Less than 12 months - Gross unrealized losses	129	258
Available-for-sale, Less than 12 months - Estimated fair value	28,134	36,551
Available-for-sale, 12 months or more - Gross unrealized losses	560	687
Available-for-sale, 12 months or more - Estimated fair value	2,916	4,616
Available-for-sale, Total - Gross unrealized losses	689	945
Available-for-sale, Total - Estimated fair value	31,050	41,167
Agency Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	2,631	4,510
Available-for-sale, Less than 12 months - Estimated fair value	139,038	295,694
Available-for-sale, 12 months or more - Gross unrealized losses	4,508	3,833
Available-for-sale, 12 months or more - Estimated fair value	287,134	101,188
Available-for-sale, Total - Gross unrealized losses	7,139	8,343
Available-for-sale, Total - Estimated fair value	426,172	396,882
Agency Guaranteed Mortgage-Backed Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	438	1,914
Available-for-sale, Less than 12 months - Estimated fair value	178,832	425,114
Available-for-sale, 12 months or more - Gross unrealized losses	176	191
Available-for-sale, 12 months or more - Estimated fair value	12,750	12,124
Available-for-sale, Total - Gross unrealized losses	614	2,105
Available-for-sale, Total - Estimated fair value	191,582	437,238
Small Business Administration Loan-Backed Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	4,551	5,869
Available-for-sale, Less than 12 months - Estimated fair value	460,629	495,817
Available-for-sale, 12 months or more - Gross unrealized losses	4,007	3,022
Available-for-sale, 12 months or more - Estimated fair value	264,312	175,523
Available-for-sale, Total - Gross unrealized losses	8,558	8,891
Available-for-sale, Total - Estimated fair value	724,941	671,340
Mutual Funds And Other [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	646	1,044
Available-for-sale, Less than 12 months - Estimated fair value	72,296	71,907
Available-for-sale, 12 months or more - Gross unrealized losses	0	0
Available-for-sale, 12 months or more - Estimated fair value	0	0
Available-for-sale, Total - Gross unrealized losses	646	1,044
Available-for-sale, Total - Estimated fair value	72,296	71,907
Held-to-maturity Securities [Member]
Investment [Line Items]
Held-to-maturity, Less than 12 months - Gross unrealized losses		580
Held-to-maturity, Less than 12 months - Estimated fair value		62,884
Held-to-maturity, 12 months or more - Gross unrealized losses		40,586
Held-to-maturity, 12 months or more - Estimated fair value		71,189
Held-to-maturity, Total - Gross unrealized losses		41,166
Held-to-maturity, Total - Estimated fair value		134,073
Available-for-sale Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	7,749	12,558
Available-for-sale, Less than 12 months - Estimated fair value	806,633	1,254,783
Available-for-sale, 12 months or more - Gross unrealized losses	159,669	129,717
Available-for-sale, 12 months or more - Estimated fair value	1,013,150	699,056
Available-for-sale, Total - Gross unrealized losses	167,418	142,275
Available-for-sale, Total - Estimated fair value	1,819,783	1,953,839
Asset-backed Securities [Member] | Trust Preferred Securities - Banks And Insurance [Member]
Investment [Line Items]
Held-to-maturity, Less than 12 months - Gross unrealized losses		53
Held-to-maturity, Less than 12 months - Estimated fair value		122
Held-to-maturity, 12 months or more - Gross unrealized losses		40,309
Held-to-maturity, 12 months or more - Estimated fair value		57,186
Held-to-maturity, Total - Gross unrealized losses		40,362
Held-to-maturity, Total - Estimated fair value		57,308
Available-for-sale, Less than 12 months - Gross unrealized losses	0	0
Available-for-sale, Less than 12 months - Estimated fair value	0	0
Available-for-sale, 12 months or more - Gross unrealized losses	150,418	121,984
Available-for-sale, 12 months or more - Estimated fair value	446,038	405,605
Available-for-sale, Total - Gross unrealized losses	150,418	121,984
Available-for-sale, Total - Estimated fair value	446,038	405,605
Asset-backed Securities [Member] | Auction Rate Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses		7
Available-for-sale, Less than 12 months - Estimated fair value		1,607
Available-for-sale, 12 months or more - Gross unrealized losses		0
Available-for-sale, 12 months or more - Estimated fair value		0
Available-for-sale, Total - Gross unrealized losses		7
Available-for-sale, Total - Estimated fair value		$ 1,607