Note 6 - Investment Securities (Details) - Investment Securities (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Securities Available-for-Sale
Available-for-sale Securities - Fair Value	$ 1,578,897	$ 1,586,668
Total investment securities - Amortized Cost	1,617,014	1,637,965
Total investment securities - Gross Unrealized Gains	15,372	18,511
Total investment securities - Gross Unrealized Losses	53,489	69,808
Total investment securities - Fair Value	1,578,897	1,586,668
US Treasury Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	475,139	460,095
Securities Available-for-sale, Gross Unrealized Gains	120	99
Securities Available-for-sale, Gross Unrealized Losses		1
Available-for-sale Securities - Fair Value	475,259	460,193
Collateralized Mortgage Backed Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	969,042	1,010,294
Securities Available-for-sale, Gross Unrealized Gains	1,860	7,049
Securities Available-for-sale, Gross Unrealized Losses	49,749	64,529
Available-for-sale Securities - Fair Value	921,153	952,814
Collateralized Mortgage Obligations [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	82	5,929
Securities Available-for-sale, Gross Unrealized Gains		231
Securities Available-for-sale, Gross Unrealized Losses	39	54
Available-for-sale Securities - Fair Value	43	6,106
Corporate Debt Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	165,716	154,955
Securities Available-for-sale, Gross Unrealized Gains	423	298
Securities Available-for-sale, Gross Unrealized Losses	3,458	4,949
Available-for-sale Securities - Fair Value	162,681	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	243	275
Available-for-sale Securities - Fair Value	5,757	5,725
Preferred Stock Of Government Sponsored Entities Member
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	535	569
Securities Available-for-sale, Gross Unrealized Gains	12,909	10,834
Available-for-sale Securities - Fair Value	13,444	11,403
Other Equity Securities [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	500
Securities Available-for-sale, Gross Unrealized Gains	60
Available-for-sale Securities - Fair Value	560
Total [Member]
Securities Available-for-Sale
Securities Available-for-sale, Amortized Cost	1,617,014	1,637,965
Securities Available-for-sale, Gross Unrealized Gains	15,372	18,511
Securities Available-for-sale, Gross Unrealized Losses	53,489	69,808
Available-for-sale Securities - Fair Value	1,578,897	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