Note 6 - Investment Securities (Detail) - Schedule of Investment Securities (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Securities Held-to-Maturity, Amortized Cost	$ 1,019,977	$ 1,153,504
Securities Held-to-Maturity, Gross Unrealized Gains	53,384	50,810
Securities Held-to-Maturity, Gross Unrealized Losses	284	337
Securities Held-to-Maturity, Fair Value	1,073,077	1,203,977
Securities Available-for-sale, Amortized Cost	1,173,146	1,309,521
Securities Available-for-sale, Gross Unrealized Gains	24,028	17,410
Securities Available-for-sale, Gross Unrealized Losses	30,391	32,453
Securities Available-for-sale, Fair Value	1,166,783	1,294,478
Total investment securities - Amortized Cost	2,193,123	2,463,025
Total investment securities - Gross Unrealized Gains	77,412	68,220
Total investment securities - Gross Unrealized Losses	30,675	32,790
Total investment securities - Fair Value	2,239,860	2,498,455
U.S. Government Sponsored Entities [Member]
Securities Held-to-Maturity, Amortized Cost	99,988	99,966
Securities Held-to-Maturity, Gross Unrealized Gains	445	1,406
Securities Held-to-Maturity, Gross Unrealized Losses	0	0
Securities Held-to-Maturity, Fair Value	100,433	101,372
Securities Available-for-sale, Amortized Cost	50,000	500,007
Securities Available-for-sale, Gross Unrealized Gains	182	1,226
Securities Available-for-sale, Gross Unrealized Losses	0	7
Securities Available-for-sale, Fair Value	50,182	501,226
State and Municipal Securities [Member]
Securities Held-to-Maturity, Amortized Cost	129,307	129,577
Securities Held-to-Maturity, Gross Unrealized Gains	7,490	7,053
Securities Held-to-Maturity, Gross Unrealized Losses	0	0
Securities Held-to-Maturity, Fair Value	136,797	136,630
Securities Available-for-sale, Amortized Cost		1,869
Securities Available-for-sale, Gross Unrealized Gains		59
Securities Available-for-sale, Gross Unrealized Losses		0
Securities Available-for-sale, Fair Value		1,928
Collateralized Mortgage Backed Securities [Member]
Securities Held-to-Maturity, Amortized Cost	780,709	913,990
Securities Held-to-Maturity, Gross Unrealized Gains	45,449	42,351
Securities Held-to-Maturity, Gross Unrealized Losses	0	0
Securities Held-to-Maturity, Fair Value	826,158	956,341
Securities Available-for-sale, Amortized Cost	527,100	325,706
Securities Available-for-sale, Gross Unrealized Gains	17,373	12,361
Securities Available-for-sale, Gross Unrealized Losses	5	436
Securities Available-for-sale, Fair Value	544,468	337,631
Corporate Debt Securities [Member]
Securities Held-to-Maturity, Amortized Cost	9,973	9,971
Securities Held-to-Maturity, Gross Unrealized Gains	0	0
Securities Held-to-Maturity, Gross Unrealized Losses	284	337
Securities Held-to-Maturity, Fair Value	9,689	9,634
Securities Available-for-sale, Amortized Cost	397,795	412,045
Securities Available-for-sale, Gross Unrealized Gains	339	113
Securities Available-for-sale, Gross Unrealized Losses	30,224	31,729
Securities Available-for-sale, Fair Value	367,910	380,429
US Treasury Securities [Member]
Securities Available-for-sale, Amortized Cost	159,871
Securities Available-for-sale, Gross Unrealized Gains	0
Securities Available-for-sale, Gross Unrealized Losses	36
Securities Available-for-sale, Fair Value	159,835
Collateralized Mortgage Obligations [Member]
Securities Available-for-sale, Amortized Cost	12,785	16,184
Securities Available-for-sale, Gross Unrealized Gains	521	540
Securities Available-for-sale, Gross Unrealized Losses	90	238
Securities Available-for-sale, Fair Value	13,216	16,486
Asset-backed Securities [Member]
Securities Available-for-sale, Amortized Cost	157	172
Securities Available-for-sale, Gross Unrealized Gains	0	0
Securities Available-for-sale, Gross Unrealized Losses	5	6
Securities Available-for-sale, Fair Value	152	166
Mutual Funds Member
Securities Available-for-sale, Amortized Cost	6,000	6,000
Securities Available-for-sale, Gross Unrealized Gains	122	48
Securities Available-for-sale, Gross Unrealized Losses	0	13
Securities Available-for-sale, Fair Value	6,122	6,035
Preferred Stock Of Government Sponsored Entities Member
Securities Available-for-sale, Amortized Cost	569	569
Securities Available-for-sale, Gross Unrealized Gains	1,607	1,085
Securities Available-for-sale, Gross Unrealized Losses	0	0
Securities Available-for-sale, Fair Value	2,176	1,654
Trust Preferred Securities [Member]
Securities Available-for-sale, Amortized Cost	17,401	45,501
Securities Available-for-sale, Gross Unrealized Gains	379	486
Securities Available-for-sale, Gross Unrealized Losses	31	24
Securities Available-for-sale, Fair Value	17,749	45,963
Other Equity Securities [Member]
Securities Available-for-sale, Amortized Cost	1,468	1,468
Securities Available-for-sale, Gross Unrealized Gains	3,505	1,492
Securities Available-for-sale, Gross Unrealized Losses	0	0
Securities Available-for-sale, Fair Value	$ 4,973	$ 2,960

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