INVESTMENT SECURITIES (Tables)

12 Months Ended

Dec. 31, 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 December 31 are as follows:

	2016								2015
(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	$	1,876,358	$	28,522	$	2,118	$	1,902,762	$	1,866,819	$	35,186	$	2,027	$	1,899,978
Obligations of state and political subdivisions		582,655		13,389		1,054		594,990		640,455		26,487		59		666,883
Government agency mortgage-backed securities		232,657		5,040		2,467		235,230		205,220		6,906		1,261		210,865
Corporate debt securities		5,716		2		31		5,687		16,672		66		58		16,680
Government agency collateralized mortgage obligations		9,225		310		0		9,535		12,862		446		0		13,308
Marketable equity securities		252		200		0		452		250		163		14		399
Total available-for-sale portfolio	$	2,706,863	$	47,463	$	5,670	$	2,748,656	$	2,742,278	$	69,254	$	3,419	$	2,808,113
Other Securities:
Federal Home Loan Bank common stock	$	12,191					$	12,191	$	19,317					$	19,317
Federal Reserve Bank common stock		19,781						19,781		16,050						16,050
Other equity securities		3,764						3,764		4,460						4,460
Total other securities	$	35,736					$	35,736	$	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 for less than or greater than twelve months is as follows:

As of December 31, 2016

		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	13	$	449,242	$	2,118	0	$	0	$	0	13	$	449,242	$	2,118
Obligations of state and political subdivisions	197		102,106		1,054	0		0		0	197		102,106		1,054
Government agency mortgage-backed securities	57		83,862		1,637	15		21,788		830	72		105,650		2,467
Corporate debt securities	1		2,677		31	0		0		0	1		2,677		31
Government agency collateralized mortgage obligations	0		0		0	2		2		0	2		2		0
Total available-for-sale investment portfolio	268	$	637,887	$	4,840	17	$	21,790	$	830	285	$	659,677	$	5,670

As of December 31, 2015

		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	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 December 31, 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
(000's omitted)	Amortized Cost		Fair Value
Due in one year or less	$	37,994	$	38,212
Due after one through five years		923,434		939,357
Due after five years through ten years		1,302,156		1,319,913
Due after ten years		201,145		205,957
Subtotal		2,464,729		2,503,439
Government agency mortgage-backed securities		232,657		235,230
Government agency collateralized mortgage obligations		9,225		9,535
Total	$	2,706,611	$	2,748,204

Cash Flow Information on Investment Securities

Cash flow information on investment securities for the years ended December 31 is as follows:

(000's omitted)	2016		2015		2014
Gross gains on sales of investment securities	$	0	$	3	$	0
Gross losses on sales of investment securities		0		7		0