Note 6 - Investment Securities (Tables)

6 Months Ended

Jun. 30, 2015

Investments, Debt and Equity Securities [Abstract]

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

	June 30, 2015
			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
	(In thousands)
Securities Available-for-Sale
U.S. treasury securities	$	299,911	$	199	$	-	$	300,110
U.S. government sponsored entities		49,975		152		-		50,127
Mortgage-backed securities		1,110,298		759		9,654		1,101,403
Collateralized mortgage obligations		70		-		30		40
Corporate debt securities		74,949		528		1,078		74,399
Mutual funds		6,000		-		156		5,844
Preferred stock of government sponsored entities		2,811		733		-		3,544
Other equity securities		3,628		6,606		2		10,232
Total	$	1,547,642	$	8,977	$	10,920	$	1,545,699

	December 31, 2014
			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		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	$	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	$	299,913	$	300,112
Due after one year through five years		88,156		89,227
Due after five years through ten years		45,607		44,609
Due after ten years (1)		1,113,966		1,111,751
Total	$	1,547,642	$	1,545,699

Schedule of Unrealized Loss on Investments [Table Text Block]

	June 30, 2015
	Temporarily impaired securities
	Less than 12 months				12 months or longer				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
	(Dollars in thousands)
Securities Available-for-Sale
Mortgage-backed securities	$	1,087,436	$	9,653	$	6	$	1	$	1,087,442	$	9,654
Collateralized mortgage obligations		-		-		40		30		40		30
Corporate debt securities		-		-		43,922		1,078		43,922		1,078
Mutual funds		-		-		5,844		156		5,844		156
Other equity securities		18		2		-		-		18		2
Total	$	1,087,454	$	9,655	$	49,812	$	1,265	$	1,137,266	$	10,920

	December 31, 2014
	Temporarily impaired securities
	Less than 12 months				12 months or longer				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
	(Dollars in thousands)
Securities Available-for-Sale
U.S. treasury securities	$	374,153	$	265	$	-	$	-	$	374,153	$	265
Mortgage-backed securities		-		-		425,090		6,386		425,090		6,386
Collateralized mortgage obligations		-		-		45		34		45		34
Corporate debt securities		-		-		63,753		1,247		63,753		1,247
Mutual funds		-		-		5,866		134		5,866		134
Preferred stock of government sponsored entities		2,448		3,733		-		-		2,448		3,733
Total	$	376,601	$	3,998	$	494,754	$	7,801	$	871,355	$	11,799