Note 6 - Investment Securities (Detail) - Investment Securities (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	$ 2,149,786	$ 1,290,676
Securities Available-for-sale, Gross Unrealized Gains	51,283	14,954
Securities Available-for-sale, Gross Unrealized Losses	10,773	14,150
Securities Available-for-sale, Fair Value	2,190,296	1,291,480
Total investment securities - Amortized Cost	2,149,786	2,064,444
Total investment securities - Gross Unrealized Gains	51,283	65,092
Total investment securities - Gross Unrealized Losses	10,773	14,150
Total investment securities - Fair Value	2,190,296	2,115,386
Securities Held-to-Maturity
Securities Held-to-Maturity, Amortized Cost	773,768	773,768
Securities Held-to-Maturity, Gross Unrealized Gains	50,138
Securities Held-to-Maturity, Gross Unrealized Losses	0
Securities Held-to-Maturity, Fair Value	823,906	823,906
US Treasury Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	359,880	509,748
Securities Available-for-sale, Gross Unrealized Gains	234	228
Securities Available-for-sale, Gross Unrealized Losses	0	5
Securities Available-for-sale, Fair Value	360,114	509,971
State and Municipal Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	59,805
Securities Available-for-sale, Gross Unrealized Gains	3,653
Securities Available-for-sale, Gross Unrealized Losses	0
Securities Available-for-sale, Fair Value	63,458
Securities Held-to-Maturity
Securities Held-to-Maturity, Amortized Cost	129,037
Securities Held-to-Maturity, Gross Unrealized Gains	9,268
Securities Held-to-Maturity, Gross Unrealized Losses	0
Securities Held-to-Maturity, Fair Value	138,305
Collateralized Mortgage Backed Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	1,449,816	404,505
Securities Available-for-sale, Gross Unrealized Gains	42,335	12,194
Securities Available-for-sale, Gross Unrealized Losses	1,553	5
Securities Available-for-sale, Fair Value	1,490,598	416,694
Securities Held-to-Maturity
Securities Held-to-Maturity, Amortized Cost	634,757
Securities Held-to-Maturity, Gross Unrealized Gains	40,801
Securities Held-to-Maturity, Gross Unrealized Losses	0
Securities Held-to-Maturity, Fair Value	675,558
Collateralized Mortgage Obligations [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	8,631	9,772
Securities Available-for-sale, Gross Unrealized Gains	369	430
Securities Available-for-sale, Gross Unrealized Losses	54	34
Securities Available-for-sale, Fair Value	8,946	10,168
Asset-backed Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	136	145
Securities Available-for-sale, Gross Unrealized Gains	0	0
Securities Available-for-sale, Gross Unrealized Losses	4	4
Securities Available-for-sale, Fair Value	132	141
Corporate Debt Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	264,949	349,973
Securities Available-for-sale, Gross Unrealized Gains	657	106
Securities Available-for-sale, Gross Unrealized Losses	9,149	14,102
Securities Available-for-sale, Fair Value	256,457	335,977
Securities Held-to-Maturity
Securities Held-to-Maturity, Amortized Cost	9,974
Securities Held-to-Maturity, Gross Unrealized Gains	69
Securities Held-to-Maturity, Gross Unrealized Losses	0
Securities Held-to-Maturity, Fair Value	10,043
Mutual Funds Member
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	6,000	6,000
Securities Available-for-sale, Gross Unrealized Gains	48	79
Securities Available-for-sale, Gross Unrealized Losses	13	0
Securities Available-for-sale, Fair Value	6,035	6,079
Preferred Stock Of Government Sponsored Entities Member
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	569	569
Securities Available-for-sale, Gross Unrealized Gains	3,987	1,766
Securities Available-for-sale, Gross Unrealized Losses	0	0
Securities Available-for-sale, Fair Value	4,556	2,335
Trust Preferred Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost		9,964
Securities Available-for-sale, Gross Unrealized Gains		151
Securities Available-for-sale, Gross Unrealized Losses		0
Securities Available-for-sale, Fair Value		$ 10,115

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Investment securities at fair value.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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