Note 6 - Investment Securities (Details) - Investment Securities (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Securities Available-for-Sale
Available-for-sale Securities - Fair Value	$ 1,339,989	$ 1,586,668
Total investment securities - Amortized Cost	1,354,885	1,637,965
Total investment securities - Gross Unrealized Gains	11,654	18,511
Total investment securities - Gross Unrealized Losses	26,550	69,808
Total investment securities - Fair Value	1,339,989	1,586,668
US Treasury Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	565,091	460,095
Securities Available-for-sale, Gross Unrealized Gains	73	99
Securities Available-for-sale, Gross Unrealized Losses	1	1
Available-for-sale Securities - Fair Value	565,163	460,193
Collateralized Mortgage Backed Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	680,556	1,010,294
Securities Available-for-sale, Gross Unrealized Gains	1,210	7,049
Securities Available-for-sale, Gross Unrealized Losses	24,897	64,529
Available-for-sale Securities - Fair Value	656,869	952,814
Collateralized Mortgage Obligations [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	81	5,929
Securities Available-for-sale, Gross Unrealized Gains		231
Securities Available-for-sale, Gross Unrealized Losses	35	54
Available-for-sale Securities - Fair Value	46	6,106
Corporate Debt Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	94,938	154,955
Securities Available-for-sale, Gross Unrealized Gains	848	298
Securities Available-for-sale, Gross Unrealized Losses	1,449	4,949
Available-for-sale Securities - Fair Value	94,337	150,304
Mutual Funds [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	6,000	6,000
Securities Available-for-sale, Gross Unrealized Losses	167	275
Available-for-sale Securities - Fair Value	5,833	5,725
Preferred Stock Of Government Sponsored Entities Member
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	4,611	569
Securities Available-for-sale, Gross Unrealized Gains	6,885	10,834
Securities Available-for-sale, Gross Unrealized Losses	1
Available-for-sale Securities - Fair Value	11,495	11,403
Other Equity Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	3,608
Securities Available-for-sale, Gross Unrealized Gains	2,638
Available-for-sale Securities - Fair Value	6,246
Total [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	1,354,885	1,637,965
Securities Available-for-sale, Gross Unrealized Gains	11,654	18,511
Securities Available-for-sale, Gross Unrealized Losses	26,550	69,808
Available-for-sale Securities - Fair Value	1,339,989	1,586,668
Asset-backed Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost		123
Available-for-sale Securities - Fair Value		$ 123