SECURITIES

The following tables summarize the amortized cost and estimated fair values of AFS and HTM securities, as of the dates indicated:



	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
June 30, 2017
AFS Securities:
Obligations of states and political subdivisions	$	7,235	$	157	$	—		$	7,392
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises	524,635		2,280		(5,239		)	521,676
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises	279,588		268		(4,984		)	274,872
Subordinated corporate bonds	5,483		193		—			5,676
Total AFS debt securities	816,941		2,898		(10,223		)	809,616
Equity securities	632		610		—			1,242
Total AFS securities	$	817,573	$	3,508	$	(10,223	)	$	810,858
HTM Securities:
Obligations of states and political subdivisions	$	94,340	$	1,037	$	(369	)	$	95,008
Total HTM securities	$	94,340	$	1,037	$	(369	)	$	95,008
December 31, 2016
AFS Securities:
Obligations of states and political subdivisions	$	8,848	$	153	$	—		$	9,001
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises	485,222		2,515		(7,115		)	480,622
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises	289,046		265		(5,421		)	283,890
Subordinated corporate bonds	5,481		132		—			5,613
Total AFS debt securities	788,597		3,065		(12,536		)	779,126
Equity securities	632		109		—			741
Total AFS securities	$	789,229	$	3,174	$	(12,536	)	$	779,867
HTM Securities:
Obligations of states and political subdivisions	$	94,609	$	618	$	(631	)	$	94,596
Total HTM securities	$	94,609	$	618	$	(631	)	$	94,596

Net unrealized losses on AFS securities at June 30, 2017 included in AOCI amounted to $4.4 million, net of a deferred tax benefit of $2.3 million. Net unrealized losses on AFS securities at December 31, 2016 included in AOCI amounted to $6.1 million, net of a deferred tax benefit of $3.3 million.

During the first six months of 2017, the Company purchased investment securities totaling $97.3 million, all of which were designated as AFS securities.

During the first six months of 2016, the Company purchased investment securities totaling $108.4 million. The Company designated $98.7 million as AFS securities and $9.7 million as HTM securities.

Impaired Securities

Management periodically reviews the Company’s investment portfolio 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 of investment securities that were in a continuous loss position at June 30, 2017 and December 31, 2016, 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
June 30, 2017
AFS Securities:
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises	$	364,378	$	(4,139	)	$	29,988	$	(1,100	)	$	394,366	$	(5,239	)
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises	116,495		(1,561		)	91,652		(3,423		)	208,147		(4,984		)
Total AFS securities	$	480,873	$	(5,700	)	$	121,640	$	(4,523	)	$	602,513	$	(10,223	)
HTM Securities:
Obligations of states and political subdivisions	$	20,686	$	(369	)	$	—	$	—		$	20,686	$	(369	)
Total HTM securities	$	20,686	$	(369	)	$	—	$	—		$	20,686	$	(369	)
December 31, 2016
AFS Securities:
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises	$	348,579	$	(5,780	)	$	29,496	$	(1,335	)	$	378,075	$	(7,115	)
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises	163,412		(2,906		)	74,212		(2,515		)	237,624		(5,421		)
Total AFS securities	$	511,991	$	(8,686	)	$	103,708	$	(3,850	)	$	615,699	$	(12,536	)
HTM Securities:
Obligations of states and political subdivisions	$	42,805	$	(631	)	$	—	$	—		$	42,805	$	(631	)
Total HTM securities	$	42,805	$	(631	)	$	—	$	—		$	42,805	$	(631	)

At June 30, 2017 and December 31, 2016, the Company held 187 and 209 investment securities with a fair value of $623.2 million and $658.5 million that were in an unrealized loss position totaling $10.6 million and $13.2 million, respectively, that were considered temporary. Of these, MBS and CMOs with a fair value of $121.6 million and $103.7 million were in an unrealized loss position, and have been in an unrealized loss position for 12 months or more, totaling $4.5 million and $3.9 million at June 30, 2017 and December 31, 2016, respectively. The unrealized loss was reflective of current interest rates in excess of the yield received on investments and is not indicative of an overall change in credit quality or other factors with the Company's investment portfolio. At June 30, 2017 and December 31, 2016, gross unrealized losses on the Company's AFS and HTM securities were 2% of the respective investment securities fair value.

The Company has the intent and ability to retain its investment securities in an unrealized loss position at June 30, 2017 until the decline in value has recovered.

Sale of Securities

The following table details the Company's sales of AFS securities for the period indicated below:



	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Proceeds from sales of securities	$	—	$	84	$	—	$	84
Gross realized gains	—		4		—		4
Gross realized losses	—		—		—		—

The Company did not sell any securities during the three and six months ended June 30, 2017. For the three and six months ended June 30, 2016, the Company sold certain AFS securities with a total carrying value of $80,000 and recorded net gains on the sale of AFS securities of $4,000 within non-interest income in the consolidated statements of income. The Company had not previously recorded any OTTI on these securities sold.

The cost basis of securities sold is measured on a specific identification basis.

FHLBB and FRB Stock

As of June 30, 2017 and December 31, 2016, the Company's investment in FHLBB stock was $21.8 million and $17.8 million, respectively. As of June 30, 2017 and December 31, 2016, the Company's investment in FRB stock was $5.4 million.

Securities Pledged

At June 30, 2017 and December 31, 2016, securities with an amortized cost of $606.8 million and $597.3 million and estimated fair values of $600.5 million and $589.7 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 debt securities by contractual maturity at June 30, 2017, 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 Securities
Due in one year or less	$	1,631	$	1,639
Due after one year through five years	103,620		103,833
Due after five years through ten years	162,740		162,857
Due after ten years	548,950		541,287
	$	816,941	$	809,616
HTM Securities
Due in one year or less	$	758	$	762
Due after one year through five years	4,769		4,835
Due after five years through ten years	5,043		5,140
Due after ten years	83,770		84,271
	$	94,340	$	95,008