Investment Securities

The carrying values and estimated fair values of investment securities at the periods indicated are presented below:



(In Thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
March 31, 2018
Securities available for sale
U.S. Treasury and government sponsored entities		$245,429		$—		$2,111		$243,318
Municipal securities	13,805		18		47		13,776
Corporate bonds	34,152		317		—		34,469
Collateralized loan obligations	6,000		11		1		6,010
Total securities available for sale		$299,386		$346		$2,159		$297,573
December 31, 2017
Securities available for sale
U.S. Treasury and government sponsored entities		$250,794		$3		$1,336		$249,461
Municipal securities	14,395		72		46		14,421
Corporate bonds	36,654		478		—		37,132
Collateralized loan obligations	6,000		5		—		6,005
Total securities available for sale		$307,843		$558		$1,382		$307,019

Gross unrealized losses on investment securities and the fair value of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at March 31, 2018 and December 31, 2017 were as follows:



	Less Than 12 Months				More Than 12 Months				Total
(In Thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
March 31, 2018:
Securities Available for Sale
U.S. Treasury and government sponsored entities		$120,700		$1,269		$122,618		$842		$243,318		$2,111
Collateralized loan obligations	3,000		1		—		—		3,000		1
Municipal securities	4,697		18		2,294		29		6,991		47
Total		$128,397		$1,288		$124,912		$871		$253,309		$2,159

December 31, 2017:
Securities Available for Sale
U.S. Treasury and government sponsored entities		$116,331		$496		$122,605		$840		$238,936		$1,336
Municipal securities	3,994		17		2,298		29		6,292		46
Total		$120,325		$513		$124,903		$869		$245,228		$1,382

The unrealized losses on investments in U.S. treasury and government sponsored entities, collateralized loan obligations, and municipal securities in both periods were caused by changes in interest rates. At March 31, 2018 and December 31, 2017, respectively, there were 26 and 24 available-for-sale securities with unrealized losses that have been in a loss position for less than twelve months. There were 17 securities as of March 31, 2018 and December 31, 2017 that have been in an unrealized loss position for more than twelve months. The contractual terms of the investments in a loss position do not permit the issuer to settle the securities at a price less than the amortized cost of the investment. Because it is more likely than not that the Company will hold these investments until a market price recovery or maturity, these investments are not considered other-than-temporarily impaired.

At March 31, 2018 and December 31, 2017, $51.9 million and $51.6 million in securities were pledged for deposits and borrowings, respectively.

The amortized cost and estimated fair values of debt securities and preferred stock at March 31, 2018, are distributed by contractual maturity as shown below. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Although preferred stock has no stated maturity, it is aggregated in the calculation of weighted average yields presented below in the category of investments that mature in ten years or more.



(In Thousands)	Amortized Cost		Fair Value		Weighted Average Yield
US Treasury and government sponsored entities
Within 1 year		$97,714		$97,467	1.08	%
1-5 years	147,715		145,851		1.71	%
Total		$245,429		$243,318	1.46	%
Corporate bonds
Within 1 year		$2,000		$2,000	2.37	%
1-5 years	21,703		21,891		2.63	%
5-10 years	10,449		10,578		3.05	%
Total		$34,152		$34,469	2.74	%
Collateralized loan obligations
1-5 years		$3,000		$2,999	3.04	%
Over 10 years	3,000		3,011		3.51	%
Total		$6,000		$6,010	3.27	%
Preferred stock
Over 10 years		$5,373		$5,527	6.36	%
Total		$5,373		$5,527	6.36	%
Municipal securities
Within 1 year		$3,202		$3,198	1.80	%
1-5 years	10,603		10,578		2.67	%
Total		$13,805		$13,776	2.47	%

The proceeds and resulting gains and losses, computed using specific identification, from sales of investment securities for the three months ending March 31, 2018 and 2017, are as follows:



(In Thousands)	Proceeds		Gross Gains		Gross Losses
Three Months Ended March 31, 2018
Available for sale securities		$—		$—		$—
Three Months Ended March 31, 2017
Available for sale securities		$10,010		$14		$—

A summary of interest income for the three months ending March 31, 2018 and 2017, on available for sale investment securities and marketable securities is as follows:



(In Thousands)	2018		2017
US Treasury and government sponsored entities		$890		$778
Other	360		289
Total taxable interest income		$1,250		$1,067
Municipal securities		$86		$97
Total tax-exempt interest income		$86		$97
Total		$1,336		$1,164