

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Available for sale at June 30, 2019
U.S. Government-sponsored agency securities	$	33,494	$	453	$	—	$	33,947
State and municipal	685,123		30,835		200		715,758
U.S. Government-sponsored mortgage-backed securities	642,298		8,532		607		650,223
Corporate obligations	31		—		—		31
Total available for sale	1,360,946		39,820		807		1,399,959
Held to maturity at June 30, 2019
U.S. Government-sponsored agency securities	33,865		20		66		33,819
State and municipal	310,076		10,987		22		321,041
U.S. Government-sponsored mortgage-backed securities	347,524		5,257		226		352,555
Foreign investment	1,500		—		—		1,500
Total held to maturity	692,965		16,264		314		708,915
Total Investment Securities	$	2,053,911	$	56,084	$	1,121	$	2,108,874



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Available for sale at December 31, 2018
U.S. Government-sponsored agency securities	$	13,493	$	92	$	3	$	13,582
State and municipal	605,994		5,995		5,854		606,135
U.S. Government-sponsored mortgage-backed securities	530,209		634		8,396		522,447
Corporate obligations	31		—		—		31
Total available for sale	1,149,727		6,721		14,253		1,142,195
Held to maturity at December 31, 2018
U.S. Government-sponsored agency securities	22,618		—		545		22,073
State and municipal	197,909		2,858		872		199,895
U.S. Government-sponsored mortgage-backed securities	268,860		713		3,323		266,250
Foreign investment	1,000		—		1		999
Total held to maturity	490,387		3,571		4,741		489,217
Total Investment Securities	$	1,640,114	$	10,292	$	18,994	$	1,631,412

The change in unrealized gains/losses from December 31, 2018 to June 30, 2019 is primarily due to the changes in interest rates. The longer term points on the yield curve have declined since year-end which increases the fair value of securities held in the portfolio.

The amortized cost and fair value of available for sale and held to maturity securities at June 30, 2019 and December 31, 2018, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties.



	Available for Sale				Held to Maturity
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Maturity Distribution at June 30, 2019:
Due in one year or less	$	1,131	$	1,138	$	3,784	$	3,782
Due after one through five years	3,752		3,851		46,941		46,914
Due after five through ten years	74,311		76,604		78,716		81,769
Due after ten years	639,454		668,143		216,000		223,895
	718,648		749,736		345,441		356,360
U.S. Government-sponsored mortgage-backed securities	642,298		650,223		347,524		352,555
Total Investment Securities	$	1,360,946	$	1,399,959	$	692,965	$	708,915



	Available for Sale				Held to Maturity
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Maturity Distribution at December 31, 2018
Due in one year or less	$	13,092	$	13,144	$	4,732	$	4,730
Due after one through five years	5,311		5,378		49,054		48,473
Due after five through ten years	73,280		74,411		62,873		64,163
Due after ten years	527,835		526,815		104,868		105,601
	619,518		619,748		221,527		222,967
U.S. Government-sponsored mortgage-backed securities	530,209		522,447		268,860		266,250
Total Investment Securities	$	1,149,727	$	1,142,195	$	490,387	$	489,217

The following tables show the Corporation’s gross unrealized losses and fair value, aggregated by investment category and length of time the individual securities have been in a continuous unrealized loss position at June 30, 2019, and December 31, 2018:



	Less than 12 Months				12 Months or Longer				Total
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Temporarily Impaired Available for Sale Securities at June 30, 2019
State and municipal	$	7,699	$	16	$	7,080	$	184	$	14,779	$	200
U.S. Government-sponsored mortgage-backed securities	7,791		15		75,152		592		82,943		607
Total Temporarily Impaired Available for Sale Securities	15,490		31		82,232		776		97,722		807
Temporarily Impaired Held to Maturity Securities at June 30, 2019
U.S. Government-sponsored agency securities	—		—		15,454		66		15,454		66
State and municipal	6,421		22		—		—		6,421		22
U.S. Government-sponsored mortgage-backed securities	74		—		36,614		226		36,688		226
Total Temporarily Impaired Held to Maturity Securities	6,495		22		52,068		292		58,563		314
Total Temporarily Impaired Investment Securities	$	21,985	$	53	$	134,300	$	1,068	$	156,285	$	1,121



	Less than 12 Months				12 Months or Longer				Total
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Temporarily Impaired Available for Sale Securities at December 31, 2018
U.S. Government-sponsored agency securities	$	1,490	$	3	$	—	$	—	$	1,490	$	3
State and municipal	234,431		3,958		38,028		1,896		272,459		5,854
U.S. Government-sponsored mortgage-backed securities	196,601		2,400		217,121		5,996		413,722		8,396
Total Temporarily Impaired Available for Sale Securities	432,522		6,361		255,149		7,892		687,671		14,253
Temporarily Impaired Held to Maturity Securities at December 31, 2018
U.S. Government-sponsored agency securities	—		—		22,073		545		22,073		545
State and municipal	14,952		369		16,786		503		31,738		872
U.S. Government-sponsored mortgage-backed securities	102,828		876		87,268		2,447		190,096		3,323
Foreign investment	—		—		999		1		999		1
Total Temporarily Impaired Held to Maturity Securities	117,780		1,245		127,126		3,496		244,906		4,741
Total Temporarily Impaired Investment Securities	$	550,302	$	7,606	$	382,275	$	11,388	$	932,577	$	18,994



	June 30, 2019			December 31, 2018
Investments reported at less than historical cost:
Historical cost	$	157,406		$	951,571
Fair value	156,285			932,577
Gross unrealized losses	$	1,121		$	18,994
Percent of the Corporation's investment portfolio	7.5		%	57.1		%

The Corporation's management believes the decline in fair value for these securities was temporary. Should the impairment of any of these securities become other-than-temporary, the cost basis of the investment will be reduced and the resulting loss recognized in net income during the period the other-than-temporary-impairment ("OTTI") is identified. The Corporation’s management has evaluated all securities with unrealized losses for OTTI and concluded no OTTI existed at June 30, 2019.

In determining the fair value of the investment securities portfolio, the Corporation utilizes a third party for portfolio accounting services, including market value input, for those securities classified as Level 1 and Level 2 in the fair value hierarchy. The Corporation has obtained an understanding of what inputs are being used by the vendor in pricing the portfolio and how the vendor classified these securities based upon these inputs. From these discussions, the Corporation’s management is comfortable that the classifications are proper. The Corporation has gained trust in the data for two reasons: (a) independent spot testing of the data is conducted by the Corporation through obtaining market quotes from various brokers on a periodic basis; and (b) actual gains or loss resulting from the sale of certain securities has proven the data to be accurate over time. Fair value of securities classified as Level 3 in the valuation hierarchy was determined using a discounted cash flow model that incorporated market estimates of interest rates and volatility in markets that have not been active.

The unrealized losses on the Corporation's investments in securities of state and political subdivisions and U.S. Government-Sponsored Agency securities were caused by interest rate increases. The contractual terms of those investments do not permit the issuer to settle the securities at a price less than the amortized cost basis of the investments. Because the Corporation does not intend to sell the investments and it is not more likely than not that the Corporation will be required to sell the investments before recovery of their amortized cost basis, which may be maturity, the Corporation does not consider those investments to be other-than-temporarily impaired at June 30, 2019. The state and municipal securities portfolio contains unrealized losses of $200,000 on seven securities and $22,000 on two securities in the available for sale and held to maturity portfolios, respectively. The U.S. Government-Sponsored Agency securities portfolio contains no unrealized losses in the available for sale portfolio and $66,000 on three securities in the held to maturity portfolio.

The unrealized losses on the Corporation's investment in mortgage-backed securities were a result of interest rate changes. The Corporation expects to recover the amortized cost basis over the term of the securities. Because the decline in market value is attributable to changes in interest rates and not credit quality, and because the Corporation does not intend to sell the investments and it is not more likely than not that the Corporation will be required to sell the investments before recovery of their amortized cost basis, which may be maturity, the Corporation does not consider those investments to be other-than-temporarily impaired at June 30, 2019. The mortgage-backed securities portfolio contains unrealized losses of $607,000 on twenty-nine securities and $226,000 on fourteen securities in the available for sale and held to maturity portfolios, respectively. All these securities are issued by a U.S. government-sponsored entity.