Note 4 - Investment Securities (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

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

	As of December 31, 2016
			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
	(In thousands)
Securities Available-for-Sale
U.S. treasury securities	$	489,839	$	35	$	857	$	489,017
U.S. government sponsored entities		400,000		-		9,669		390,331
Mortgage-backed securities		339,241		309		3,290		336,260
Collateralized mortgage obligations		48		-		20		28
Corporate debt securities		74,965		247		862		74,350
Mutual funds		6,500		-		270		6,230
Preferred stock of government sponsored entities		2,811		4,497		-		7,308
Other equity securities		3,608		7,213		-		10,821
Total securities available-for-sale	$	1,317,012	$	12,301	$	14,968	$	1,314,345

	As of December 31, 2015
			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		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

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	$	339,879	$	339,823
Due after one year through five years		553,130		544,585
Due after five years through ten years		75,111		72,733
Due after ten years (1)		348,892		357,204
Total	$	1,317,012	$	1,314,345

Schedule of Unrealized Loss on Investments [Table Text Block]

	As of December 31, 2016
	Temporarily Impaired Securities
	Less than 12 months						12 months or longer						Total
	Fair		Unrealized		No. of		Fair		Unrealized		No. of		Fair		Unrealized		No. of
	Value		Losses		Issuances		Value		Losses		Issuances		Value		Losses		Issuances
	(Dollars in thousands)
Securities Available-for-Sale
U.S. treasury securities	$	299,088	$	857		6	$	-	$	-		-	$	299,088	$	857		6
U.S. government sponsored entities		390,331		9,669		8		-		-		-		390,331		9,669		8
Mortgage-backed securities		328,236		3,288		16		62		2		3		328,298		3,290		19
Collateralized mortgage obligations		-		-		-		28		20		1		28		20		1
Corporate debt securities		-		-		-		29,138		862		2		29,138		862		2
Mutual funds		-		-		-		6,230		270		1		6,230		270		1
Total securities available-for-sale	$	1,017,655	$	13,814		30	$	35,458	$	1,154		7	$	1,053,113	$	14,968		37

	As of December 31, 2015
	Temporarily Impaired Securities
	Less than 12 months						12 months or longer						Total
	Fair		Unrealized		No. of		Fair		Unrealized		No. of		Fair		Unrealized		No. of
	Value		Losses		Issuances		Value		Losses		Issuances		Value		Losses		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