INVESTMENT SECURITIES (Tables)

9 Months Ended

Sep. 30, 2016

INVESTMENT SECURITIES [Abstract]

Amortized Cost and Estimated Fair Value of Investment Securities

The amortized cost and estimated fair value of investment securities as of September 30, 2016 and December 31, 2015 are as follows:

	September 30, 2016								December 31, 2015
			Gross		Gross						Gross		Gross
	Amortized		Unrealized		Unrealized		Fair		Amortized		Unrealized		Unrealized		Fair
(000's omitted)	Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
Available-for-Sale Portfolio:
U.S. Treasury and agency securities	$	1,873,698	$	102,914	$	0	$	1,976,612	$	1,866,819	$	35,186	$	2,027	$	1,899,978
Obligations of state and political subdivisions		595,376		28,847		1		624,222		640,455		26,487		59		666,883
Government agency mortgage-backed securities		216,942		8,033		242		224,733		205,220		6,906		1,261		210,865
Corporate debt securities		5,735		39		0		5,774		16,672		66		58		16,680
Government agency collateralized mortgage obligations		10,086		418		0		10,504		12,862		446		0		13,308
Marketable equity securities		251		178		19		410		250		163		14		399
Total available-for-sale portfolio	$	2,702,088	$	140,429	$	262	$	2,842,255	$	2,742,278	$	69,254	$	3,419	$	2,808,113
Other Securities:
Federal Home Loan Bank common stock	$	11,682					$	11,682	$	19,317					$	19,317
Federal Reserve Bank common stock		19,781						19,781		16,050						16,050
Other equity securities		3,926						3,926		4,460						4,460
Total other securities	$	35,389					$	35,389	$	39,827					$	39,827

Summary of Investment Securities That Have Been in a Continuous Unrealized Loss Position for Less Than or Greater Than Twelve Months

A summary of investment securities that have been in a continuous unrealized loss position is as follows:

As of September 30, 2016

	Less than 12 Months						12 Months or Longer						Total
					Gross						Gross						Gross
			Fair		Unrealized				Fair		Unrealized				Fair		Unrealized
(000's omitted)		#	Value		Losses			#	Value		Losses			#	Value		Losses
Available-for-Sale Portfolio:
Obligations of state and political subdivisions		4	$	1,987	$	1		0	$	0	$	0		4	$	1,987	$	1
Government agency mortgage-backed securities		9		10,116		40		15		23,228		202		24		33,344		242
Government agency collateralized mortgage obligations		0		0		0		2		2		0		2		2		0
Marketable equity securities		0		0		0		1		82		19		1		82		19
Total available-for-sale investment portfolio		13	$	12,103	$	41		18	$	23,312	$	221		31	$	35,415	$	262

As of December 31, 2015

	Less than 12 Months						12 Months or Longer						Total
					Gross						Gross						Gross
			Fair		Unrealized				Fair		Unrealized				Fair		Unrealized
(000's omitted)		#	Value		Losses			#	Value		Losses			#	Value		Losses
Available-for-Sale Portfolio:
U.S. Treasury and agency obligations		9	$	353,844	$	2,027		0	$	0	$	0		9	$	353,844	$	2,027
Obligations of state and political subdivisions		18		8,804		34		2		735		25		20		9,539		59
Government agency mortgage-backed securities		17		24,178		161		19		30,103		1,100		36		54,281		1,261
Corporate debt securities		1		3,024		0		1		2,710		58		2		5,734		58
Government agency collateralized mortgage obligations		0		0		0		2		3		0		2		3		0
Marketable equity securities		1		87		14		0		0		0		1		87		14
Total available-for-sale investment portfolio		46	$	389,937	$	2,236		24	$	33,551	$	1,183		70	$	423,488	$	3,419

Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity

The amortized cost and estimated fair value of debt securities at September 30, 2016, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.  Securities not due at a single maturity date are shown separately.

	Available-for-Sale
	Amortized		Fair
(000's omitted)	Cost		Value
Due in one year or less	$	34,640	$	34,835
Due after one through five years		872,160		910,105
Due after five years through ten years		1,360,056		1,440,555
Due after ten years		207,953		221,113
Subtotal		2,474,809		2,606,608
Government agency mortgage-backed securities		216,942		224,733
Government agency collateralized mortgage obligations		10,086		10,504
Total	$	2,701,837	$	2,841,845