Securities (Schedule Of Amortized Cost And Fair Value Of Securities Held To Maturity) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 1,203,240	$ 917,212
Gross Unrealized Gains	38,917	36,700
Gross Unrealized Losses	(1,201)	(1,879)
Securities Held To Maturity, Fair Value	1,240,956	952,033
U.S. Treasury And Other U.S. Government Agencies And Corporations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	4,399	4,523
Gross Unrealized Gains	413	360
Securities Held To Maturity, Fair Value	4,812	4,883
Agency Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	915,239	683,100
Gross Unrealized Gains	31,300	28,722
Gross Unrealized Losses	(16)
Securities Held To Maturity, Fair Value	946,523	711,822
Agency Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	109,107	54,319
Gross Unrealized Gains	967	573
Gross Unrealized Losses		(11)
Securities Held To Maturity, Fair Value	110,074	54,881
Non-Agency Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	17,814	24,348
Gross Unrealized Gains	97	143
Gross Unrealized Losses	(940)	(1,373)
Securities Held To Maturity, Fair Value	16,971	23,118
Commercial Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,025
Gross Unrealized Gains	13
Securities Held To Maturity, Fair Value	1,038
States Of The U.S. And Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	153,525	147,748
Gross Unrealized Gains	6,127	6,877
Gross Unrealized Losses	(116)
Securities Held To Maturity, Fair Value	159,536	154,625
Collateralized Debt Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	808	1,592
Gross Unrealized Losses	(108)	(314)
Securities Held To Maturity, Fair Value	700	1,278
Other Debt Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,323	1,582
Gross Unrealized Gains		25
Gross Unrealized Losses	(21)	(181)
Securities Held To Maturity, Fair Value	$ 1,302	$ 1,426