Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Investment [Line Items]
Less than 12 months, Fair Value	$ 2,384,676	$ 3,012,123
Less than 12 months, Unrealized Losses	48,362	75,636
12 months or longer, Fair Value	482,454	421,202
12 months or longer, Unrealized Losses	32,703	42,542
Total, Fair Value	2,867,130	3,433,325
Total, Unrealized Losses	81,065	118,178
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	29,349	96,172
Less than 12 months, Unrealized Losses	27	243
12 months or longer, Fair Value	30,928	59,677
12 months or longer, Unrealized Losses	5,270	12,901
Total, Fair Value	60,277	155,849
Total, Unrealized Losses	5,297	13,144
Government-Sponsored Enterprise Obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	481,558	487,317
Less than 12 months, Unrealized Losses	11,182	18,155
12 months or longer, Fair Value	106,412	93,654
12 months or longer, Unrealized Losses	7,614	9,126
Total, Fair Value	587,970	580,971
Total, Unrealized Losses	18,796	27,281
State And Municipal Obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	387,791	478,818
Less than 12 months, Unrealized Losses	8,018	15,520
12 months or longer, Fair Value	189,058	178,150
12 months or longer, Unrealized Losses	17,018	17,825
Total, Fair Value	576,849	656,968
Total, Unrealized Losses	25,036	33,345
Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	759,734	717,778
Less than 12 months, Unrealized Losses	19,716	26,124
12 months or longer, Fair Value	107	0
12 months or longer, Unrealized Losses	3	0
Total, Fair Value	759,841	717,778
Total, Unrealized Losses	19,719	26,124
Non-Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	56,501	53,454
Less than 12 months, Unrealized Losses	563	918
12 months or longer, Fair Value	22,388	22,289
12 months or longer, Unrealized Losses	574	702
Total, Fair Value	78,889	75,743
Total, Unrealized Losses	1,137	1,620
Asset-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	583,899	1,088,556
Less than 12 months, Unrealized Losses	5,535	9,072
12 months or longer, Fair Value	118,267	58,398
12 months or longer, Unrealized Losses	1,188	1,097
Total, Fair Value	702,166	1,146,954
Total, Unrealized Losses	6,723	10,169
Total Mortgage And Asset-Backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	1,400,134	1,859,788
Less than 12 months, Unrealized Losses	25,814	36,114
12 months or longer, Fair Value	140,762	80,687
12 months or longer, Unrealized Losses	1,765	1,799
Total, Fair Value	1,540,896	1,940,475
Total, Unrealized Losses	27,579	37,913
Debt Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	85,844	90,028
Less than 12 months, Unrealized Losses	3,321	5,604
12 months or longer, Fair Value	15,294	9,034
12 months or longer, Unrealized Losses	1,036	891
Total, Fair Value	101,138	99,062
Total, Unrealized Losses	$ 4,357	$ 6,495