The following table summarizes the amortized costs and estimated fair values of AFS and HTM securities, as of the dates indicated:



	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2018
AFS Investments (carried at fair value):
Obligations of states and political subdivisions	$	94,430	$	216	$	(894	)	$	93,752
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises	466,613		583		(13,524		)	453,672
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises	351,958		1,007		(10,071		)	342,894
Subordinated corporate bonds	20,398		23		(47		)	20,374
Total AFS investments	$	933,399	$	1,829	$	(24,536	)	$	910,692
HTM Investments (carried at amortized cost):
Obligations of states and political subdivisions	$	1,307	$	8	$	(24	)	$	1,291
Total HTM investments	$	1,307	$	8	$	(24	)	$	1,291
December 31, 2017
AFS Investments (carried at fair value):
Obligations of states and political subdivisions	$	7,232	$	103	$	—		$	7,335
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises	510,176		597		(7,471		)	503,302
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises	279,575		14		(6,790		)	272,799
Subordinated corporate bonds	5,484		173		—			5,657
Equity investments⁽¹⁾	554		252		—			806
Total AFS investments	$	803,021	$	1,139	$	(14,261	)	$	789,899
HTM Securities (carried at amortized cost):
Obligations of states and political subdivisions	$	94,073	$	1,077	$	(237	)	$	94,913
Total HTM investments	$	94,073	$	1,077	$	(237	)	$	94,913

(1)

As of December 31, 2017, equity investments with a readily determinable fair value were designated and presented as AFS investments on the consolidated statements of condition. Upon adoption of ASU 2016-01, effective January 1, 2018, these investments were no longer eligible for designation, accounting and presentation as AFS. At December 31, 2018, the Company's equity investments with a readily determinable fair value were presented within other investments on the consolidated statements of condition. Refer to Note 1 for further details.

At December 31, 2018 and 2017, net unrealized losses on AFS investments included in AOCI amounted to $17.8 million, net of a deferred tax benefit of $4.9 million, and $10.3 million, net of a deferred tax benefit of $2.8 million, respectively.

For the year ended December 31, 2018 and 2017, the Company purchased debt investments of $232.2 million and $170.5 million, respectively, all of which were designated as AFS investments.

Impaired AFS and HTM Investments

Management periodically reviews the Company’s AFS and HTM investments to determine the cause, magnitude and duration of declines in the fair value of each security. Thorough evaluations of the causes of the unrealized losses are performed to determine whether the impairment is temporary or other-than-temporary in nature. Considerations such as the ability of the securities to meet cash flow requirements, levels of credit enhancements, risk of curtailment, and recoverability of invested amount over a reasonable period of time, and the length of time the security is in a loss position, for example, are applied in determining OTTI. Once a decline in value is determined to be other-than-temporary, the cost basis of the security is permanently reduced and a corresponding charge to earnings is recognized.

The following table presents the estimated fair values and gross unrealized losses on AFS and HTM investments that were in a continuous loss position at December 31, 2018 and 2017, by length of time that individual securities in each category have been in a continuous loss position:



	Less Than 12 Months					12 Months or More					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
December 31, 2018
AFS Investments:
Obligations of states and political subdivisions	$	36,218	$	(281	)	$	28,437	$	(613	)	$	64,655	$	(894	)
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises	46,459		(252		)	364,430		(13,272		)	410,889		(13,524		)
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises	5,956		(40		)	227,461		(10,031		)	233,417		(10,071		)
Subordinated corporate bonds	11,378		(26		)	966		(21		)	12,344		(47		)
Total AFS investments	$	100,011	$	(599	)	$	621,294	$	(23,937	)	$	721,305	$	(24,536	)
HTM Investments:
Obligations of states and political subdivisions	$	509	$	(5	)	$	411	$	(19	)	$	920	$	(24	)
Total HTM investments	$	509	$	(5	)	$	411	$	(19	)	$	920	$	(24	)
December 31, 2017
AFS Investments:
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises	$	221,466	$	(2,393	)	$	233,971	$	(5,078	)	$	455,437	$	(7,471	)
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises	102,612		(696		)	164,389		(6,094		)	267,001		(6,790		)
Total AFS investments	$	324,078	$	(3,089	)	$	398,360	$	(11,172	)	$	722,438	$	(14,261	)
HTM Investments:
Obligations of states and political subdivisions	$	9,317	$	(57	)	$	9,436	$	(180	)	$	18,753	$	(237	)
Total HTM investments	$	9,317	$	(57	)	$	9,436	$	(180	)	$	18,753	$	(237	)

At December 31, 2018 and 2017, the Company held 302 and 209 debt investments classified as AFS and HTM with a fair value of $722.2 million and $741.2 million that were in an unrealized loss position totaling $24.6 million and $14.5 million, respectively, that were considered temporary. Of these, MBS and CMOs with a fair value of $591.9 million and $398.4 million were in an unrealized loss position, and have been in an unrealized loss position for 12 months or more totaling $23.3 million and $11.2 million at December 31, 2018 and 2017, respectively. The unrealized loss was reflective of current interest rates in excess of the yield received on debt investments and is not indicative of an overall change in credit quality or other factors with the Company's AFS and HTM investment portfolio. At December 31, 2018 and 2017, gross unrealized losses on the Company's AFS and HTM investments were 3.4% and 2%, respectively, of its respective fair value.

The Company has the intent and ability to retain its debt investments in an unrealized loss position at December 31, 2018 until the decline in value has recovered.

Sale of AFS Investments

The following table details the Company’s sales of investments for the period indicated below:



	For The Year Ended December 31,
	2018			2017			2016
Proceeds from sales of AFS investments	$	56,155		$	20,366		$	28,850
Gross realized gains	32			869			125
Gross realized losses	(695		)	(14		)	(74		)

For the year ended December 31, 2018, 2017, and 2016, the Company sold certain AFS investments with a total carrying value of $56.8 million, $19.5 million, and $28.8 million, respectively, and recorded net (losses) gains on the sale of AFS investments of ($663,000), $855,000, and $51,000, respectively, within non-interest income in the consolidated statements of income. The Company had not previously recorded any OTTI on these securities sold.

AFS and HTM Investments Pledged

At December 31, 2018 and 2017, AFS and HTM investments with an amortized cost of $734.1 million and $702.5 million, respectively, and estimated fair values of $714.4 million and $691.2 million, respectively, were pledged to secure FHLBB advances, public deposits, and securities sold under agreements to repurchase, and for other purposes required or permitted by law.

Contractual Maturities

The amortized cost and estimated fair values of AFS and HTM investments by contractual maturity at December 31, 2018 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.



	Amortized Cost		Fair Value
AFS Investments
Due in one year or less	$	17,046	$	16,987
Due after one year through five years	68,064		66,560
Due after five years through ten years	247,274		241,539
Due after ten years	601,015		585,606
	$	933,399	$	910,692
HTM Investments
Due in one year or less	$	—	$	—
Due after one year through five years	—		—
Due after five years through ten years	1,307		1,291
Due after ten years	—		—
	$	1,307	$	1,291