Securities (Schedule Of Amortized Cost And Fair Value Of Securities Held To Maturity) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 1,151,743	$ 917,212
Gross Unrealized Gains	44,744	36,700
Gross Unrealized Losses	(128)	(1,879)
Securities Held To Maturity, Fair Value	1,196,359	952,033
U.S. Treasury And Other U.S. Government Agencies And Corporations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	14,336	4,523
Gross Unrealized Gains	450	360
Gross Unrealized Losses	(10)
Securities Held To Maturity, Fair Value	14,776	4,883
Agency Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	862,530	683,100
Gross Unrealized Gains	36,082	28,722
Securities Held To Maturity, Fair Value	898,612	711,822
Agency Collateralized Mortgage obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	101,770	54,319
Gross Unrealized Gains	1,238	573
Gross Unrealized Losses		(11)
Securities Held To Maturity, Fair Value	103,008	54,881
Non-Agency Collateralized Mortgage obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	15,603	24,348
Gross Unrealized Gains	136	143
Gross Unrealized Losses	(13)	(1,373)
Securities Held To Maturity, Fair Value	15,726	23,118
Commercial Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,024
Gross Unrealized Gains	45
Securities Held To Maturity, Fair Value	1,069
States Of The U.S. And Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	154,372	147,748
Gross Unrealized Gains	6,793	6,877
Gross Unrealized Losses	(7)
Securities Held To Maturity, Fair Value	161,158	154,625
Collateralized Debt Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	787	1,592
Gross Unrealized Losses	(87)	(314)
Securities Held To Maturity, Fair Value	700	1,278
Other Debt Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,321	1,582
Gross Unrealized Gains		25
Gross Unrealized Losses	(11)	(181)
Securities Held To Maturity, Fair Value	$ 1,310	$ 1,426