AVAILABLE-FOR-SALE SECURITIES (Tables)

12 Months Ended

Dec. 31, 2016

AVAILABLE-FOR-SALE SECURITIES [Abstract]

Amortized cost and estimated fair values of available-for-sale securities

	2016
		Gross	Gross	Estimated
	Amortized	Unrealized	Unrealized	Fair
	Cost	Gains	Losses	Value
	(In thousands)
U.S. Government agencies	$   1,794,231	$        1,261	$        6,065	$   1,789,427
U.S. Government agency issued residential
mortgage-backed securities	176,476	1,665	1,898	176,243
U.S. Government agency issued commercial
mortgage-backed securities	171,840	1,648	1,209	172,279
Obligations of states and political subdivisions	346,609	15,547	2,151	360,005
FHLB and other securities	32,436	1,286	-	33,722
Total	$   2,521,592	$      21,407	$      11,323	$   2,531,676
	2015
		Gross	Gross	Estimated
	Amortized	Unrealized	Unrealized	Fair
	Cost	Gains	Losses	Value
	(In thousands)
U.S. Government agencies	$   1,246,261	$           826	$        2,447	$   1,244,640
U.S. Government agency issued residential
mortgage-backed securities	138,759	1,957	176	140,540
U.S. Government agency issued commercial
mortgage-backed securities	261,544	2,414	3,265	260,693
Obligations of states and political subdivisions	394,769	22,813	83	417,499
FHLB and other securities	18,112	845	-	18,957
Total	$   2,059,445	$      28,855	$        5,971	$   2,082,329

Amortized cost and estimated fair value of available-for-sale securities by contractual maturity

		Estimated	Weighted
	Amortized	Fair	Average
	Cost	Value	Yield
	(Dollars in thousands)
Maturing in one year or less	$      548,060	$      548,347	0.96	%
Maturing after one year through five years	1,331,619	1,326,489	1.30
Maturing after five years through ten years	53,517	54,418	5.71
Maturing after ten years	240,080	253,900	5.47
Mortgage-backed securities	348,316	348,522	2.13
Total	$   2,521,592	$   2,531,676

Temporarily impaired available-for-sale securities with continuous unrealized loss positions

	2016
	Less Than 12 Months		12 Months or Longer		Total
	Fair	Unrealized	Fair	Unrealized	Fair	Unrealized
	Value	Losses	Value	Losses	Value	Losses
	(In thousands)
U.S. Government agencies	$      1,082,573	$            6,065	$                    -	$                   -	$      1,082,573	$            6,065
U.S. Government agency issued residential
mortgage-backed securities	71,599	1,783	15,375	115	86,974	1,898
U.S. Government agency issued commercial
mortgage-backed securities	129,940	1,084	14,385	125	144,325	1,209
Obligations of states and political subdivisions	46,798	2,151	-	-	46,798	2,151
Total	$      1,330,910	$          11,083	$           29,760	$               240	$      1,360,670	$          11,323
	2015
	Less Than 12 Months		12 Months or Longer		Total
	Fair	Unrealized	Fair	Unrealized	Fair	Unrealized
	Value	Losses	Value	Losses	Value	Losses
	(In thousands)
U.S. Government agencies	$         762,568	$            2,447	$                    -	$                   -	$         762,568	$            2,447
U.S. Government agency issued residential
mortgage-backed securities	34,238	176	-	-	34,238	176
U.S. Government agency issued commercial
mortgage-backed securities	193,621	2,710	31,166	555	224,787	3,265
Obligations of states and political subdivisions	13,576	70	2,856	13	16,432	83
Total	$      1,004,003	$            5,403	$           34,022	$               568	$      1,038,025	$            5,971