INVESTMENT SECURITIES

The following tables detail the amortized cost and the estimated fair value of our available-for-sale and held-to-maturity investment securities:



(Dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Available-for-sale securities:
December 31, 2017
CMO	$	250,592	$	88	$	4,141	$	246,539
FNMA MBS	479,218		941		6,172		473,987
FHLMC MBS	88,681		118		924		87,875
GNMA MBS	29,300		209		411		29,098
Other investments	643		—		20		623
	$	848,434	$	1,356	$	11,668	$	838,122
December 31, 2016
GSE	$	35,061	$	9	$	60	$	35,010
CMO	264,607		566		3,957		261,216
FNMA MBS	414,218		950		9,404		405,764
FHLMC MBS	64,709		135		1,330		63,514
GNMA MBS	28,540		303		427		28,416
Other investments	626		—		3		623
	$	807,761	$	1,963	$	15,181	$	794,543

(Dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Held-to-Maturity Securities :⁽¹⁾
December 31, 2017
State and political subdivisions	$	161,186	$	1,758	$	91	$	162,853
December 31, 2016
State and political subdivisions	$	164,346	$	271	$	1,385	$	163,232

(1)

Held-to-maturity securities transferred from available-for-sale are included in held-to-maturity at fair value at the time of transfer. The amortized cost of held-to-maturity securities included net unrealized gains of $1.6 million and $2.2 million at December 31, 2017 and December 31, 2016, respectively, related to securities transferred, which are offset in Accumulated Other Comprehensive (Loss) Income, net of tax.

The scheduled maturities of investment securities available for sale and held to maturity at December 31, 2017 and December 31, 2016 are presented in the table below:



	Available for Sale
(Dollars in thousands)	Amortized Cost		Fair Value
2017 ⁽¹⁾⁽²⁾
Within one year	$	—	$	—
After one year but within five years	20,051		19,825
After five years but within ten years	179,812		175,583
After ten years	647,928		642,091
	$	847,791	$	837,499
2016 ⁽¹⁾
Within one year	$	16,009	$	16,017
After one year but within five years	19,052		18,992
After five years but within ten years	276,635		270,300
After ten years	495,439		488,611
	$	807,135	$	793,920

	Held to Maturity
(Dollars in thousands)	Amortized Cost		Fair Value
2017 ⁽¹⁾
Within one year	$	322	$	320
After one year but within five years	5,895		5,894
After five years but within ten years	18,751		18,873
After ten years	136,218		137,766
	$	161,186	$	162,853
2016 ⁽¹⁾
Within one year	$	—	$	—
After one year but within five years	6,168		6,162
After five years but within ten years	8,882		8,870
After ten years	149,296		148,200
	$	164,346	$	163,232


(1)	Actual maturities could differ from contractual maturities.


(2)	Included in the investment portfolio, but not in the table above, is a mutual fund with an amortized cost and fair value as of December 31, 2017 of $0.6 million and $0.6 million, respectively, which has no stated maturity.

MBS have expected maturities that differ from their contractual maturities. These differences arise because borrowers have the right to call or prepay obligations with or without a prepayment penalty.

Investment securities with fair market values aggregating $688.2 million and $562.5 million were pledged as collateral for retail customer repurchase agreements, municipal deposits, and other obligations as of December 31, 2017 and 2016, respectively.

During 2017, we sold $457.0 million of investment securities categorized as available for sale, resulting in realized gains of $2.1 million and realized losses of less than $0.1 million. During 2016, we sold $201.8 million of investment securities categorized as available for sale, resulting in realized gains of $2.4 million and less than $0.1 million of realized losses. The cost basis of all investment securities sales is based on the specific identification method. During 2015, we sold $192.8 million of investment securities categorized as available for sale, resulting in realized gains of $1.5 million and less than $0.1 million of realized losses. the cost basis of all investment securities sales is based on the specific identification method.

As of December 31, 2017, and December 31, 2016, our investment securities portfolio had remaining unamortized premiums of $14.1 million and $18.0 million, respectively, and unaccreted discounts of $1.3 million and $0.4 million, respectively.

For those investment securities with unrealized losses, the table below shows our gross unrealized losses and fair value by investment category and length of time that individual securities were in a continuous unrealized loss position at December 31, 2017.



	Duration of Unrealized Loss Position
	Less than 12 months				12 months or longer				Total
(Dollars in thousands) Available-for-sale securities:	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
CMO	$	146,726	$	1,820	$	77,149	$	2,321	$	223,875	$	4,141
FHLMC MBS	204,921		1,479		126,342		4,693		331,263		6,172
FNMA MBS	42,514		269		21,405		655		63,919		924
GNMA MBS	4,615		56		14,782		355		19,397		411
Other investments	—		—		624		20		624		20
Total temporarily impaired investments	$	398,776	$	3,624	$	240,302	$	8,044	$	639,078	$	11,668
	Less than 12 months				12 months or longer				Total
(Dollars in thousands) Held-to-maturity securities	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
State and political subdivisions	$	23,404	$	59	$	5,625	$	32	$	29,029	$	91
Total temporarily impaired investments	$	23,404	$	59	$	5,625	$	32	$	29,029	$	91



	Less than 12 months				12 months or longer				Total
(Dollars in thousands)	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
Available-for-sale securities:	Value		Loss		Value		Loss		Value		Loss
GSE	$	21,996	$	60	$	—	$	—	$	21,996	$	60
CMO	160,572		3,867		4,654		90		165,226		3,957
FNMA MBS	50,878		1,330		—		—		50,878		1,330
FHLMC MBS	300,403		9,404		—		—		300,403		9,404
GNMA MBS	16,480		427		—		—		16,480		427
Other investments	623		3		—		—		623		3
Total temporarily impaired investments	$	550,952	$	15,091	$	4,654	$	90	$	555,606	$	15,181
	Less than 12 months				12 months or longer				Total
(Dollars in thousands)	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
Held-to-maturity securities	Value		Loss		Value		Loss		Value		Loss
State and political subdivisions	$	112,642	$	1,374	$	695	$	11	$	113,337	$	1,385
Total temporarily impaired investments	$	112,642	$	1,374	$	695	$	11	$	113,337	$	1,385

At December 31, 2017, we owned investment securities totaling $668.1 million for which the amortized cost basis exceeded fair value. Total unrealized losses on these securities were $11.8 million at December 31, 2017. The temporary impairment is the result of changes in market interest rates subsequent to the purchase of the securities. Our investment portfolio is reviewed each quarter for indications of other than temporary impairment. This review includes analyzing the length of time and the extent to which the fair value has been lower than the amortized cost, the financial condition and near-term prospects of the issuer, including any specific events which may influence the operations of the issuer and our intent and ability to hold the investment for a period of time sufficient to allow for full recovery of the unrealized loss. We evaluate our intent and ability to hold securities based upon our investment strategy for the particular type of security and our cash flow needs, liquidity position, capital adequacy and interest rate risk position. In addition, we do not have the intent to sell, nor is it more likely-than-not we will be required to sell these securities before we are able to recover the amortized cost basis.

All securities, with the exception of one having a fair value of $0.8 million at December 31, 2017, were AA- rated or better at the time of purchase and remained investment grade at December 31, 2017. All securities were evaluated for OTTI at December 31, 2017 and 2016. The result of this evaluation showed no OTTI as of December 31, 2017 or 2016. The weighted average duration of MBS was 5.2 years at December 31, 2017.