Note 11 - Fair Value Measurements (Details) - Assets and Liabilities Measured at Fair Value on a Recurring Basis - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Securities available-for-sale
Securities available-for-sale	$ 1,545,699	$ 1,318,935
Assets	1,548,057	1,320,838
Liabilities
Liabilities	7,296	9,633
US Treasury Securities [Member]
Securities available-for-sale
Securities available-for-sale	300,110	664,004
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale
Securities available-for-sale	50,127
Collateralized Mortgage Backed Securities [Member]
Securities available-for-sale
Securities available-for-sale	1,101,403	544,303
Collateralized Mortgage Obligations [Member]
Securities available-for-sale
Securities available-for-sale	40	45
Corporate Debt Securities [Member]
Securities available-for-sale
Securities available-for-sale	74,399	94,472
Mutual Funds [Member]
Securities available-for-sale
Securities available-for-sale	5,844	5,866
Preferred Stock of Government Sponsored Entities [Member]
Securities available-for-sale
Securities available-for-sale	3,544	3,224
Other Equity Securities [Member]
Securities available-for-sale
Securities available-for-sale	10,232	7,021
Warrant [Member]
Securities available-for-sale
Assets	32	27
Foreign Exchange Contract [Member]
Securities available-for-sale
Assets	2,326	1,876
Liabilities
Liabilities	3,201	5,007
Interest Rate Swap [Member]
Liabilities
Liabilities	4,095	4,626
Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
Securities available-for-sale	305,954	669,870
Assets	305,954	669,870
Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]
Securities available-for-sale
Securities available-for-sale	300,110	664,004
Fair Value, Inputs, Level 1 [Member] | Mutual Funds [Member]
Securities available-for-sale
Securities available-for-sale	5,844	5,866
Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Securities available-for-sale	1,239,745	649,065
Assets	1,242,071	650,941
Liabilities
Liabilities	7,296	9,633
Fair Value, Inputs, Level 2 [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale
Securities available-for-sale	50,127
Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Backed Securities [Member]
Securities available-for-sale
Securities available-for-sale	1,101,403	544,303
Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Obligations [Member]
Securities available-for-sale
Securities available-for-sale	40	45
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Securities available-for-sale
Securities available-for-sale	74,399	94,472
Fair Value, Inputs, Level 2 [Member] | Preferred Stock of Government Sponsored Entities [Member]
Securities available-for-sale
Securities available-for-sale	3,544	3,224
Fair Value, Inputs, Level 2 [Member] | Other Equity Securities [Member]
Securities available-for-sale
Securities available-for-sale	10,232	7,021
Fair Value, Inputs, Level 2 [Member] | Foreign Exchange Contract [Member]
Securities available-for-sale
Assets	2,326	1,876
Liabilities
Liabilities	3,201	5,007
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Liabilities
Liabilities	4,095	4,626
Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Assets	32	27
Fair Value, Inputs, Level 3 [Member] | Warrant [Member]
Securities available-for-sale
Assets	$ 32	$ 27