Note (4)—Investment securities:

The amortized cost of securities and their fair values at December 31, 2017 and 2016 are shown below:

	December 31, 2017
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
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 securities		7,870		1		(149	)		7,722
Total securities available-for-sale	$	548,898	$	3,067	$	(7,973	)	$	543,992

	December 31, 2016
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Securities Available-for-Sale
Debt securities
U.S. government agency securities	$	998	$	—	$	(13	)	$	985
Mortgage-backed securities - residential		450,874		939		(7,905	)		443,908
Municipals, tax exempt		116,034		3,003		(2,114	)		116,923
Treasury securities		11,809		—		(52	)		11,757
Total debt securities		579,715		3,942		(10,084	)		573,573
Equity securities		8,744		1		(135	)		8,610
Total securities available-for-sale	$	588,459	$	3,943	$	(10,219	)	$	582,183

Securities pledged at December 31, 2017 and 2016 had a carrying amount of $337,604 and $390,814, 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 December 31, 2017 and 2016 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.

	Year Ended December 31,
	2017				2016
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	905	$	925	$	9,290	$	9,352
Due in one to five years		28,332		28,878		25,520		26,340
Due in five to ten years		19,218		19,588		31,122		32,248
Due in over ten years		67,016		68,098		62,909		61,725
		115,471		117,489		128,841		129,665
Mortgage-backed securities - residential		425,557		418,781		450,874		443,908
Total debt securities	$	541,028	$	536,270	$	579,715	$	573,573

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

	Year Ended December 31,
	2017		2016
Proceeds from sales	$	94,743	$	271,148
Gross realized gains		1,277		4,755
Gross realized losses		48		348
Other-than-temporary-impairment	945			—

The Company also recognized $1 on gains related to the early call of available for sale securities during the year ended December 31, 2017.

The following tables show gross unrealized losses at December 31, 2017 and 2016, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	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

	December 31, 2016
	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	$	985	$	13	$	—	$	—	$	985	$	13
Mortgage-backed securities - residential		390,595		7,230		19,073		675		409,668		7,905
Municipals, tax exempt		43,132		2,114		—		—		43,132		2,114
Treasury securities		10,256		52		—		—		10,256		52
Total debt securities		444,968		9,409		19,073		675		464,041		10,084
Equity securities		—		—		3,126		135		3,126		135
	$	444,968	$	9,409	$	22,199	$	810	$	467,167	$	10,219

As of December 31, 2017 and 2016, the Company’s securities portfolio consisted of 294 and 329 securities, 124 and 151 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. 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.

When impairment of an equity security is considered to be other-than-temporary, the security is written down to its fair value and an impairment loss is recorded as a loss within noninterest income. The Company evaluated the near-term prospects of the equity investments in relation to the severity and duration of the impairment. Based on that evaluation, the Company concluded that it was probable that there had been adverse cash flows for one of the equity investments held. Additionally, the Company does not intend to hold the security long-term and it is unlikely the fair value would be recovered. Credit impairment losses of $945 and $0 was recognized during the years ended December 31, 2017 and 2016, respectively. Changes in the amount of credit related losses recognized in earnings for which OTTI has been recognized are as follows:

Balance as of January 1, 2017	$	—
Additions related to credit losses for which OTTI was not previously recognized		(945	)
Reductions for securities sold during the period		—
Reductions for securities where there is an intent to sell or requirement to sell		—
Increases in credit loss for which OTTI was previously recognized		—
Reductions for increases in cash flows expected to be collected		—
Balance as of December 31, 2017	$	(945	)