INVESTMENT SECURITIES (Tables)

12 Months Ended

Dec. 31, 2019

INVESTMENT SECURITIES [Abstract]

Amortized Cost and Estimated Fair Value of Investment Securities

The amortized cost and estimated fair value of investment securities as of December 31 are as follows:

	2019								2018
(000's omitted)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Available-for-Sale Portfolio:
U.S. Treasury and agency securities	$	2,030,060	$	21,674	$	7,975	$	2,043,759	$	2,036,474	$	2,190	$	14,911	$	2,023,753
Obligations of state and political subdivisions		497,852		14,382		26		512,208		453,640		6,563		1,049		459,154
Government agency mortgage-backed securities		428,491		5,478		1,107		432,862		390,234		1,526		9,283		382,477
Corporate debt securities		2,527		1		0		2,528		2,588		0		42		2,546
Government agency collateralized mortgage obligations		52,621		482		32		53,071		69,342		60		1,283		68,119
Total available-for-sale portfolio	$	3,011,551	$	42,017	$	9,140	$	3,044,428	$	2,952,278	$	10,339	$	26,568	$	2,936,049
Equity and other Securities:
Equity securities, at fair value	$	251	$	200	$	0	$	451	$	251	$	200	$	19	$	432
Federal Home Loan Bank common stock		7,246		0		0		7,246		8,768		0		0		8,768
Federal Reserve Bank common stock		30,922		0		0		30,922		30,690		0		0		30,690
Other equity securities, at adjusted cost		4,546		750		0		5,296		4,969		750		0		5,719
Total equity and other securities	$	42,965	$	950	$	0	$	43,915	$	44,678	$	950	$	19	$	45,609

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 for less than or greater than twelve months is as follows:

As of December 31, 2019

	Less than 12 Months						12 Months or Longer						Total
(000's omitted)		#	Fair Value		Gross Unrealized Losses			#	Fair Value		Gross Unrealized Losses			#	Fair Value		Gross Unrealized Losses
Available-for-Sale Portfolio:
U.S. Treasury and agency securities		12	$	592,678	$	7,970		5	$	25,998	$	5		17	$	618,676	$	7,975
Obligations of state and political subdivisions		21		22,716		26		0		0		0		21		22,716		26
Government agency mortgage-backed securities		50		89,237		341		52		52,975		766		102		142,212		1,107
Government agency collateralized mortgage obligations		5		5,971		14		5		4,405		18		10		10,376		32
Total available-for-sale investment portfolio		88	$	710,602	$	8,351		62	$	83,378	$	789		150	$	793,980	$	9,140

As of December 31, 2018

	Less than 12 Months						12 Months or Longer						Total
(000's omitted)		#	Fair Value		Gross Unrealized Losses			#	Fair Value		Gross Unrealized Losses			#	Fair Value		Gross Unrealized Losses
Available-for-Sale Portfolio:
U.S. Treasury and agency securities		7	$	473,082	$	682		64	$	1,213,276	$	14,229		71	$	1,686,358		14,911
Obligations of state and political subdivisions		118		55,671		216		97		51,753		833		215		107,424		1,049
Government agency mortgage-backed securities		43		47,708		258		181		253,931		9,025		224		301,639		9,283
Corporate debt securities		0		0		0		1		2,546		42		1		2,546		42
Government agency collateralized mortgage obligations		1		66		0		41		63,112		1,283		42		63,178		1,283
Total available-for-sale investment portfolio		169	$	576,527	$	1,156		384	$	1,584,618	$	25,412		553	$	2,161,145	$	26,568
Equity and other Securities:
Equity securities, at fair value		1	$	82	$	19		0	$	0	$	0		1	$	82	$	19
Total equity and other securities		1	$	82	$	19		0	$	0	$	0		1	$	82	$	19

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

The amortized cost and estimated fair value of debt securities at December 31, 2019, 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
(000's omitted)	Amortized Cost		Fair Value
Due in one year or less	$	677,169	$	680,805
Due after one through five years		905,531		925,987
Due after five years through ten years		453,320		456,833
Due after ten years		494,419		494,870
Subtotal		2,530,439		2,558,495
Government agency mortgage-backed securities		428,491		432,862
Government agency collateralized mortgage obligations		52,621		53,071
Total	$	3,011,551	$	3,044,428