NOTE D: INVESTMENT SECURITIES

The amortized cost and estimated fair value of investment securities as of September 30, 2017 and December 31, 2016 are as follows:

	September 30, 2017								December 31, 2016
(000's omitted)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Available-for-Sale Portfolio:
U.S. Treasury and agency securities	$	2,040,820	$	33,703	$	382	$	2,074,141	$	1,876,358	$	28,522	$	2,118	$	1,902,762
Obligations of state and political subdivisions		540,810		17,175		26		557,959		582,655		13,389		1,054		594,990
Government agency mortgage-backed securities		342,838		4,398		2,314		344,922		232,657		5,040		2,467		235,230
Corporate debt securities		2,663		0		1		2,662		5,716		2		31		5,687
Government agency collateralized mortgage obligations		93,922		275		148		94,049		9,225		310		0		9,535
Marketable equity securities		251		276		0		527		252		200		0		452
Total available-for-sale portfolio	$	3,021,304	$	55,827	$	2,871	$	3,074,260	$	2,706,863	$	47,463	$	5,670	$	2,748,656

Other Securities:
Federal Home Loan Bank common stock	$	8,837					$	8,837	$	12,191					$	12,191
Federal Reserve Bank common stock		30,690						30,690		19,781						19,781
Certificates of deposit		5,581						5,581		0						0
Other equity securities		5,850						5,850		3,764						3,764
Total other securities	$	50,958					$	50,958	$	35,736					$	35,736

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

As of September 30, 2017

	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		24	$	201,051	$	382		0	$	0	$	0		24	$	201,051	$	382
Obligations of state and political subdivisions		9		4,386		21		1		365		5		10		4,751		26
Government agency mortgage-backed securities		94		142,538		1,049		27		35,781		1,265		121		178,319		2,314
Corporate debt securities		1		2,662		1		0		0		0		1		2,662		1
Government agency collateralized mortgage obligations		27		62,406		148		2		2		0		29		62,408		148
Total available-for-sale investment portfolio		155	$	413,043	$	1,601		30	$	36,148	$	1,270		185	$	449,191	$	2,871

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

The unrealized losses reported pertaining to securities issued by the U.S. government and its sponsored entities, include treasuries, agencies, and mortgage-backed securities issued by Ginnie Mae, Fannie Mae, and Freddie Mac, which are currently rated AAA by Moody’s Investor Services, AA+ by Standard & Poor’s and are guaranteed by the U.S. government. The majority of the obligations of state and political subdivisions and corporations carry a credit rating of A or better. Additionally, a majority of the obligations of state and political subdivisions carry a secondary level of credit enhancement. The Company does not intend to sell these securities, nor is it more likely than not that the Company will be required to sell these securities prior to recovery of the amortized cost. The unrealized losses in the portfolios are primarily attributable to changes in interest rates. As such, management does not believe any individual unrealized loss as of September 30, 2017 represents OTTI.

The amortized cost and estimated fair value of debt securities at September 30, 2017, 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	$	43,083	$	43,270
Due after one through five years		1,507,979		1,531,059
Due after five years through ten years		832,917		852,985
Due after ten years		200,314		207,448
Subtotal		2,584,293		2,634,762
Government agency mortgage-backed securities		342,838		344,922
Government agency collateralized mortgage obligations		93,922		94,049
Total	$	3,021,053	$	3,073,733

As of September 30, 2017, $310.7 million of U.S. Treasury securities were pledged as collateral for securities sold under agreement to repurchase. All securities sold under agreement to repurchase as of September 30, 2017 have an overnight and continuous maturity.