Note 11 - Fair Value Measurements (Details) - Assets and Liabilities Measured at Fair Value on a Recurring Basis (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Securities available-for-sale
Available-for-sale Securities - Fair Value	$ 1,578,897	$ 1,586,668
Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	481,576	465,917
Total Assets	481,576	465,917
Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	1,097,321	1,120,751
Total Assets	1,102,417	1,131,869
Liabilities
Total Liabilities	3,324	6,140
Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Total Assets	28	30
Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	1,578,897	1,586,668
Total Assets	1,584,021	1,597,816
Liabilities
Total Liabilities	3,324	6,140
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	475,259	460,193
US Treasury Securities [Member] | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	475,259	460,193
US Treasury Securities [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	475,259	460,193
Mortgage-backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	921,153	952,815
Mortgage-backed Securities [Member] | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	921,153	952,815
Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	43	6,106
Collateralized Mortgage Obligations [Member] | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	43	6,106
Collateralized Mortgage Obligations [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	43	6,106
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	162,681	150,304
Corporate Debt Securities [Member] | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	162,681	150,304
Corporate Debt Securities [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	162,681	150,304
Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	5,757	5,724
Mutual Funds [Member] | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	5,757	5,724
Mutual Funds [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	5,757	5,725
Preferred Stock Of Government Sponsored Entities Member | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	13,444	11,403
Preferred Stock Of Government Sponsored Entities Member | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	13,444	11,403
Preferred Stock Of Government Sponsored Entities Member
Securities available-for-sale
Available-for-sale Securities - Fair Value	13,444	11,403
Other Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	560
Other Equity Securities [Member] | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	560
Other Equity Securities [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value	560
Warrant [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Total Assets	28	30
Warrant [Member] | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Total Assets	28	30
Option Contracts Member | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Total Assets	3
Liabilities
Total Liabilities	2
Option Contracts Member | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Total Assets	3
Liabilities
Total Liabilities	2
Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Total Assets	5,093	6,182
Liabilities
Total Liabilities	3,322	6,140
Foreign Exchange Contract [Member] | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Total Assets	5,093	6,182
Liabilities
Total Liabilities	3,322	6,140
Trust Preferred Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value		123
Trust Preferred Securities [Member] | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Available-for-sale Securities - Fair Value		123
Trading Securities Member | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Total Assets		4,936
Trading Securities Member | Estimate of Fair Value Measurement [Member]
Securities available-for-sale
Total Assets		$ 4,936