Note 4 - Investment Securities (Tables)

12 Months Ended

Dec. 31, 2015

Investments, Debt and Equity Securities [Abstract]

Schedule of Available-for-sale Securities Reconciliation [Table Text Block]

	As of December 31, 2015
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
Securities Available-for-Sale
U.S. treasury securities	$	284,678	$	5	$	395		284,288
U.S. government sponsored entities		150,000		-		1,840		148,160
Mortgage-backed securities		1,073,108		560		11,399		1,062,269
Collateralized mortgage obligations		63		-		27		36
Corporate debt securities		74,955		425		1,525		73,855
Mutual funds		6,000		-		167		5,833
Preferred stock of government sponsored entities		2,811		633		228		3,216
Other equity securities		4,108		4,929		342		8,695
Total securities available-for-sale	$	1,595,723	$	6,552	$	15,923	$	1,586,352

	As of December 31, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
Securities Available-for-Sale
U.S. treasury securities	$	664,206	$	63	$	265		664,004
Mortgage-backed securities		549,296		1,393		6,386		544,303
Collateralized mortgage obligations		79		-		34		45
Corporate debt securities		94,943		776		1,247		94,472
Mutual funds		6,000				134		5,866
Preferred stock of government sponsored entities		6,276		681		3,733		3,224
Other equity securities		3,608		3,413				7,021
Total securities available-for-sale	$	1,324,408	$	6,326	$	11,799	$	1,318,935

Investments Classified by Contractual Maturity Date [Table Text Block]

	Securities Available-for-Sale
	Amortized Cost		Fair Value
	(In thousands)
Due in one year or less	$	184,963	$	184,956
Due after one year through five years		135,698		135,924
Due after five years through ten years		195,539		192,291
Due after ten years (1)		1,079,523		1,073,181
Total	$	1,595,723	$	1,586,352

Schedule of Unrealized Loss on Investments [Table Text Block]

	As of December 15, 2015
	Temporarily Impaired Securities
	Less than 12 months						12 months or longer						Total
	Fair Value		Unrealized Losses		No. of Issuances		Fair Value		Unrealized Losses		No. of Issuances		Fair Value		Unrealized Losses		No. of Issuances
	(Dollars in thousands)
Securities Available-for-Sale
U.S. treasury securities	$	224,289	$	395		5	$	-	$	-		-	$	224,289	$	395		5
U.S. government sponsored entities		148,160		1,840		3		-		-		-		148,160		1,840		3
Mortgage-backed securities		1,025,342		11,398		35		6		1		2		1,025,348		11,399		37
Collateralized mortgage obligations		-		-		-		36		27		1		36		27		1
Corporate debt securities		9,950		50		1		43,525		1,475		3		53,475		1,525		4
Mutual funds		-		-		-		5,833		167		1		5,833		167		1
Preferred stock of government sponsored entities		2,488		228		2		-		-		-		2,488		228		2
Other equity securities		158		342		1		-		-		-		158		342		1
Total securities available-for-sale	$	1,410,387	$	14,253		47	$	49,400	$	1,670		7	$	1,459,787	$	15,923		54

	As of December 31, 2014
	Temporarily Impaired Securities
	Less than 12 months						12 months or longer						Total
	Fair Value		Unrealized Losses		No. of Issuances		Fair Value		Unrealized Losses		No. of Issuances		Fair Value		Unrealized Losses		No. of Issuances
	(Dollars in thousands)
Securities Available-for-Sale
U.S. treasury securities	$	374,153	$	265		6	$	-	$	-		-	$	374,153	$	265		6
Mortgage-backed securities		-		-		-		425,090		6,386		16		425,090		6,386		16
Collateralized mortgage obligations		-		-		-		45		34		1		45		34		1
Corporate debt securities		-		-		-		63,753		1,247		4		63,753		1,247		4
Mutual funds		-		-		-		5,866		134		1		5,866		134		1
Preferred stock of government sponsored entities		2,448		3,733		2		-		-		-		2,448		3,733		2
Total securities available-for-sale	$	376,601	$	3,998		8	$	494,754	$	7,801		22	$	871,355	$	11,799		30