Note (3)—Investment securities:

The amortized cost of securities and their fair values at March 31, 2018 and December 31, 2017 are shown below:

	March 31, 2018
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Investment Securities
Available-for-sale debt securities
U.S. government agency securities	$	999	$	—	$	(17	)	$	982
Mortgage-backed securities - residential		486,907		237		(14,214	)		472,930
Municipals, tax exempt		113,492		1,582		(1,916	)		113,158
Treasury securities		7,356		—		(178	)		7,178
Total	$	608,754	$	1,819	$	(16,325	)	$	594,248

As of March 31, 2018, the Company also had $3,099 in marketable equity securities recorded at fair value. A loss of $38 was recognized due to changes in fair value of these securities during the three months ended March 31, 2018. As of January 1, 2018, the Company adopted ASU 2016-01 (See Note 1) and reclassified $3,604 of other securities without readily determinable market values to other assets.

	December 31, 2017
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Investment Securities
Available-for-sale debt securities
U.S. government agency securities	$	999	$	—	$	(13	)	$	986
Mortgage-backed securities - residential		425,557		374		(7,150	)		418,781
Municipals, tax exempt		107,127		2,692		(568	)		109,251
Treasury securities		7,345		—		(93	)		7,252
Total debt securities		541,028		3,066		(7,824	)		536,270
Equity and other securities		7,870		1		(149	)		7,722
Total investment securities	$	548,898	$	3,067	$	(7,973	)	$	543,992

Securities pledged at March 31, 2018 and December 31, 2017 had a carrying amount of $427,995 and $337,604, respectively, and were pledged to secure Federal Home Loan Bank advances, a Federal Reserve Bank line of credit, public deposits and repurchase agreements.

The amortized cost and fair value of debt securities by contractual maturity at March 31, 2018 and December 31, 2017 are shown below. Maturities may differ from contractual maturities in mortgage-backed securities because the mortgage underlying the security may be called or repaid without any penalties. Therefore, mortgage-backed securities are not included in the maturity categories in the following maturity summary.

	March 31, 2018				December 31, 2017
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	5,715	$	5,841	$	905	$	925
Due in one to five years		24,165		24,396		28,332		28,878
Due in five to ten years		19,817		19,960		19,218		19,588
Due in over ten years		72,150		71,121		67,016		68,098
		121,847		121,318		115,471		117,489
Mortgage-backed securities - residential		486,907		472,930		425,557		418,781
Total debt securities	$	608,754	$	594,248	$	541,028	$	536,270

Sales and impairment of available-for-sale securities were as follows:

	Three Months Ended March 31,
	2018		2017
Proceeds from sales	$	221	$	—
Gross realized gains		—		—
Gross realized losses		9		—

The Company also recognized $1 in gains related to the early call of available for sale securities during the three months ended March 31, 2017.

The following tables show gross unrealized losses at March 31, 2018 and December 31, 2017, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	March 31, 2018
	Less than 12 months				12 months or more				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized loss
U.S. government agency securities	$	—	$	—	$	982	$	17	$	982	$	17
Mortgage-backed securities - residential		163,771		3,236		274,285		10,978		438,056		14,214
Municipals, tax exempt		30,104		762		19,186		1,154		49,290		1,916
Treasury securities		7,177		178		—		—		7,177	$	178
Total debt securities	$	201,052	$	4,176	$	294,453	$	12,149	$	495,505	$	16,325

	December 31, 2017
	Less than 12 months				12 months or more				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized loss
U.S. government agency securities	$	—	$	—	$	986	$	13	$	986	$	13
Mortgage-backed securities - residential		107,611		980		290,258		6,170		397,869		7,150
Municipals, tax exempt		7,354		101		20,112		467		27,466		568
Treasury securities		7,252		93		—		—		7,252		93
Total debt securities		122,217		1,174		311,356		6,650		433,573		7,824
Equity securities		—		—		3,050		149		3,050		149
	$	122,217	$	1,174	$	314,406	$	6,799	$	436,623	$	7,973

As of March 31, 2018 and December 31, 2017, the Company’s securities portfolio consisted of 307 and 294 securities, 171 and 124 of which were in an unrealized loss position, respectively.

The Company evaluates securities with unrealized losses for other-than-temporary impairment (OTTI) on a quarterly basis and recorded no OTTI for the three months ended March 31, 2018 and 2017. Impairment is assessed at the individual security level. The Company considers an investment security impaired if the fair value of the security is less than its cost or amortized cost basis. For debt securities, the unrealized losses associated with these investment securities are primarily driven by interest rates and are not due to the credit quality of the securities. The Company currently does not intend to sell those investments with unrealized losses, and it is unlikely that the Company will be required to sell the investments before recovery of their amortized cost bases, which may be maturity.

As of March 31, 2018, the Company had a trade date payable related to securities purchases amounting to $3,912 that had not yet settled.