Note (3)—Investment securities:

The amortized cost of securities and their fair values at September 30, 2017 and December 31, 2016 are shown below:

	September 30, 2017
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Securities Available-for-Sale
Debt securities
U.S. government agency securities	$	999	$	—	$	(7	)	$	992
Mortgage-backed securities - residential		423,174		586		(4,966	)		418,794
Municipals, tax exempt		104,957		2,657		(664	)		106,950
Treasury securities		8,836		—		(17	)		8,819
Total debt securities		537,966		3,243		(5,654	)		535,555
Equity securities		7,853		1		(127	)		7,727
Total securities available-for-sale	$	545,819	$	3,244	$	(5,781	)	$	543,282

	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 September 30, 2017 and December 31, 2016 had a carrying amount of $349,685 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 September 30, 2017 and December 31, 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.

	September 30, 2017				December 31, 2016
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	2,036	$	2,037	$	9,290	$	9,352
Due in one to five years		27,722		28,535		25,520		26,340
Due in five to ten years		17,362		17,851		31,122		32,248
Due in over ten years		67,672		68,338		62,909		61,725
		114,792		116,761		128,841		129,665
Mortgage-backed securities - residential		423,174		418,794		450,874		443,908
Total debt securities	$	537,966	$	535,555	$	579,715	$	573,573

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Proceeds from sales	$	82,585	$	1,668	$	94,743	$	270,663
Gross realized gains		1,199		416		1,276		4,755
Gross realized losses		—		—		48		348
Other-than-temporary-impairment	945			—	945			—

The Company also recognized $1 in gains related to the early call of available for sale securities during the nine months ended September 30, 2017.

The following tables show gross unrealized losses at September 30, 2017 and December 31, 2016, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	September 30, 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	$	—	$	—	$	993	$	7	$	993	$	7
Mortgage-backed securities - residential		354,240		3,800		40,115		1,166		394,355		4,966
Municipals, tax exempt		35,240		493		4,155		171		39,395		664
Treasury securities		8,819		17		—		—		8,819	$	17
Total debt securities		398,299		4,310		45,263		1,344		443,562		5,654
Equity securities		—		—		3,054		127		3,054		127
	$	398,299	$	4,310	$	48,317	$	1,471	$	446,616	$	5,781

	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 September 30, 2017 and December 31, 2016, the Company’s securities portfolio consisted of 288 and 329 securities, 134 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. As such, a credit impairment loss of $945 was recognized as of September 30, 2017. 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 sale or requirement to sale		—
Increases in credit loss for which OTTI was previously recognized		—
Reductions for increases in cash flows expected to be collected		—
Balance as of September 30, 2017	$	(945	)