Securities (Schedule Of Amortized Cost And Fair Value Of Securities Held To Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 1,178,558	$ 917,212
Gross Unrealized Gains	36,420	36,700
Gross Unrealized Losses	(2,152)	(1,879)
Securities Held To Maturity, Fair Value	1,212,826	952,033
U.S. Treasury And Other U.S. Government Agencies And Corporations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	4,441	4,523
Gross Unrealized Gains	340	360
Securities Held To Maturity, Fair Value	4,781	4,883
Agency Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	888,484	683,100
Gross Unrealized Gains	29,006	28,722
Gross Unrealized Losses	(471)
Securities Held To Maturity, Fair Value	917,019	711,822
Agency Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	115,104	54,319
Gross Unrealized Gains	731	573
Gross Unrealized Losses	(88)	(11)
Securities Held To Maturity, Fair Value	115,747	54,881
Non-Agency Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	19,652	24,348
Gross Unrealized Gains	107	143
Gross Unrealized Losses	(1,313)	(1,373)
Securities Held To Maturity, Fair Value	18,446	23,118
States Of The U.S. And Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	147,990	147,748
Gross Unrealized Gains	6,236	6,877
Gross Unrealized Losses	(81)
Securities Held To Maturity, Fair Value	154,145	154,625
Collateralized Debt Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,563	1,592
Gross Unrealized Losses	(176)	(314)
Securities Held To Maturity, Fair Value	1,387	1,278
Other Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,324	1,582
Gross Unrealized Gains		25
Gross Unrealized Losses	(23)	(181)
Securities Held To Maturity, Fair Value	$ 1,301	$ 1,426