Note 6 - Investment Securities (Details) - Temporarily Impaired Securities (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Securities Available-for-Sale
Investment Securities - Less than 12 Months - Fair Value	$ 914,384	$ 877,208
Investment Securities - Less than 12 Months - Unrealized Losses	49,750	64,562
Investment Securities - 12 Months or longer - Fair Value	102,495	106,378
Investment Securities- 12 Months or longer - Unrealized Losses	3,739	5,246
Investment Securities - Fair Value	1,016,879	983,586
Investment Securities - Unrealized Losses	53,489	69,808
Collateralized Mortgage Backed Securities [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value	888,606	792,012
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses	49,748	64,526
Securities Available-for-Sale - 12 Months or longer - Fair Value	151	272
Securities Available-for-Sale - 12 Months or longer - Unrealized Losses	1	2
Securities Available-for-Sale - Fair Value	888,757	792,284
Securities Available-for-Sale - Unrealized Losses	49,749	64,528
Collateralized Mortgage Obligations [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value		68
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses		4
Securities Available-for-Sale - 12 Months or longer - Fair Value	43	301
Securities Available-for-Sale - 12 Months or longer - Unrealized Losses	39	50
Securities Available-for-Sale - Fair Value	43	369
Securities Available-for-Sale - Unrealized Losses	39	54
Corporate Debt Securities [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value	25,778	9,970
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses	2	30
Securities Available-for-Sale - 12 Months or longer - Fair Value	96,544	100,081
Securities Available-for-Sale - 12 Months or longer - Unrealized Losses	3,456	4,919
Securities Available-for-Sale - Fair Value	122,322	110,051
Securities Available-for-Sale - Unrealized Losses	3,458	4,949
Mutual Funds [Member]
Securities Available-for-Sale
Securities Available-for-Sale - 12 Months or longer - Fair Value	5,757	5,724
Securities Available-for-Sale - 12 Months or longer - Unrealized Losses	243	275
Securities Available-for-Sale - Fair Value	5,757	5,724
Securities Available-for-Sale - Unrealized Losses	243	275
Total [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value	914,384	877,208
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses	49,750	64,562
Securities Available-for-Sale - 12 Months or longer - Fair Value	102,495	106,378
Securities Available-for-Sale - 12 Months or longer - Unrealized Losses	3,739	5,246
Securities Available-for-Sale - Fair Value	1,016,879	983,586
Securities Available-for-Sale - Unrealized Losses	53,489	69,808
US Treasury Securities [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value		75,064
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses		1
Securities Available-for-Sale - Fair Value		75,064
Securities Available-for-Sale - Unrealized Losses		1
Mortgage Backed Securities Non Agency [Member]
Securities Available-for-Sale
Securities Available-for-Sale - Less than 12 Months - Fair Value		94
Securities Available-for-Sale - Less than 12 Months - Unrealized Losses		1
Securities Available-for-Sale - Fair Value		94
Securities Available-for-Sale - Unrealized Losses		$ 1