Deposits (Schedule Of Deposits) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Deposits [Line Items]
Total non-interest-bearing demand deposits, balance	$ 6,784,112	$ 6,672,555	$ 5,413,002
Total non-interest-bearing demand deposits, Percentage of Total	40.10%	39.80%	36.80%
Total interest-bearing deposits, balance	10,124,909	10,084,193	9,296,557
Total interest-bearing deposits, Percentage of Total	59.90%	60.20%	63.20%
Total deposits, balance	16,909,021	16,756,748	14,709,559
Total deposits, Percentage of Total	100.00%	100.00%	100.00%
Private Accounts [Member]
Deposits [Line Items]
Savings and interest checking, balance	2,950,197	2,912,937	2,484,668
Savings and interest checking, Percentage of Total	17.40%	17.40%	16.90%
Money market accounts, balance	5,750,104	5,664,780	5,243,830
Money market accounts, Percentage of Total	34.00%	33.80%	35.60%
Time accounts of $100,000 or more, balance	532,544	533,682	609,166
Time accounts of $100,000 or more, Percentage of Total	3.20%	3.20%	4.20%
Time accounts under $100,000, balance	500,623	522,887	546,167
Time accounts under $100,000, Percentage of Total	3.00%	3.10%	3.70%
Total private accounts, balance	9,733,468	9,634,286	8,883,831
Total private accounts, Percentage of Total	57.60%	57.50%	60.40%
Commercial And Individual [Member]
Deposits [Line Items]
Total non-interest-bearing demand deposits, balance	6,006,806	5,848,840	4,903,053
Total non-interest-bearing demand deposits, Percentage of Total	35.50%	34.90%	33.30%
Correspondent Banks [Member]
Deposits [Line Items]
Total non-interest-bearing demand deposits, balance	331,114	370,275	290,099
Total non-interest-bearing demand deposits, Percentage of Total	2.00%	2.20%	2.00%
Public Funds [Member]
Deposits [Line Items]
Total non-interest-bearing demand deposits, balance	446,192	453,440	219,850
Total non-interest-bearing demand deposits, Percentage of Total	2.60%	2.70%	1.50%
Savings and interest checking, balance	208,760	265,747	183,752
Savings and interest checking, Percentage of Total	1.20%	1.60%	1.30%
Money market accounts, balance	42,488	44,590	85,745
Money market accounts, Percentage of Total	0.30%	0.30%	0.60%
Time accounts of $100,000 or more, balance	136,817	136,422	139,221
Time accounts of $100,000 or more, Percentage of Total	0.80%	0.80%	0.90%
Time accounts under $100,000, balance	3,376	3,148	4,008
Total public funds, balance	$ 391,441	$ 449,907	$ 412,726
Total public funds, Percentage of Total	2.30%	2.70%	2.80%