Investment Securities Available-For-Sale

The following table shows investment securities available-for-sale.



(Dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
March 31, 2018
U.S. Treasury and Federal agencies securities	$	510,739	$	7	$	(7,749	)	$	502,997
U.S. States and political subdivisions securities	98,740		321		(1,076		)	97,985
Mortgage-backed securities — Federal agencies	301,717		997		(6,384		)	296,330
Corporate debt securities	44,584		—		(528		)	44,056
Foreign government and other securities	700		8		—			708
Total debt securities available-for-sale	$	956,480	$	1,333	$	(15,737	)	$	942,076

December 31, 2017
U.S. Treasury and Federal agencies securities	$	471,508	$	57	$	(3,446	)	$	468,119
U.S. States and political subdivisions securities	116,260		648		(908		)	116,000
Mortgage-backed securities — Federal agencies	289,327		1,456		(2,873		)	287,910
Corporate debt securities	31,573		5		(284		)	31,294
Foreign government and other securities	700		10		—			710
Total debt securities available-for-sale	$	909,368	$	2,176	$	(7,511	)	$	904,033

At March 31, 2018 and December 31, 2017, the residential mortgage-backed securities held by the Company consisted primarily of GNMA, FNMA and FHLMC pass-through certificates which are guaranteed by those respective agencies of the United States government (Government Sponsored Enterprise, GSEs).

The following table shows the contractual maturities of investments in debt securities available-for-sale at March 31, 2018. Expected maturities will differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.



(Dollars in thousands)	Amortized Cost		Fair Value
Due in one year or less	$	73,984	$	73,935
Due after one year through five years	560,259		551,743
Due after five years through ten years	20,520		20,068
Due after ten years	—		—
Mortgage-backed securities	301,717		296,330
Total debt securities available-for-sale	$	956,480	$	942,076

The following table summarizes gross unrealized losses and fair value by investment category and age.



	Less than 12 Months					12 months or Longer					Total
(Dollars in thousands)	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
March 31, 2018
U.S. Treasury and Federal agencies securities	$	399,359	$	(4,388	)	$	88,465	$	(3,361	)	$	487,824	$	(7,749	)
U.S. States and political subdivisions securities	46,927		(484		)	18,067		(592		)	64,994		(1,076		)
Mortgage-backed securities - Federal agencies	175,903		(3,672		)	67,169		(2,712		)	243,072		(6,384		)
Corporate debt securities	34,146		(184		)	9,910		(344		)	44,056		(528		)
Foreign government and other securities	—		—			—		—			—		—
Total debt securities available-for-sale	$	656,335	$	(8,728	)	$	183,611	$	(7,009	)	$	839,946	$	(15,737	)

December 31, 2017
U.S. Treasury and Federal agencies securities	$	311,865	$	(1,161	)	$	89,617	$	(2,285	)	$	401,482	$	(3,446	)
U.S. States and political subdivisions securities	34,971		(287		)	24,909		(621		)	59,880		(908		)
Mortgage-backed securities - Federal agencies	137,169		(1,336		)	60,162		(1,537		)	197,331		(2,873		)
Corporate debt securities	13,747		(57		)	10,048		(227		)	23,795		(284		)
Foreign government and other securities	—		—			—		—			—		—
Total debt securities available-for-sale	$	497,752	$	(2,841	)	$	184,736	$	(4,670	)	$	682,488	$	(7,511	)

The initial indication of potential other-than-temporary-impairment (OTTI) for debt securities is a decline in fair value below amortized cost. Quarterly, the impaired securities are analyzed on a qualitative and quantitative basis in determining OTTI. Declines in the fair value of debt securities available-for-sale below their cost that are deemed to be other-than-temporary are reflected in earnings as realized losses to the extent the impairment is related to credit losses. The amount of impairment related to other factors is recognized in other comprehensive income. In estimating OTTI losses, the Company considers among other things, (i) the length of time and the extent to which fair value has been less than cost, (ii) the financial condition and near-term prospects of the issuer, and (iii) whether it is more likely than not that the Company will not have to sell any such securities before a recovery of cost.

At March 31, 2018, the Company does not have the intent to sell any of the debt securities available-for-sale in the table above and believes that it is more likely than not, that it will not have to sell any such securities before an anticipated recovery of cost. Primarily the unrealized losses on debt securities are due to increases in market rates over the yields available at the time the underlying securities were purchased. The fair value is expected to recover on all debt securities as they approach their maturity date or re-pricing date or if market yields for such investments decline. The Company does not believe any of the securities are impaired due to reasons of credit quality.

The following table shows the gross realized gains and losses from the securities available-for-sale portfolio, including marketable equity securities. Realized gains and losses of all securities are computed using the specific identification cost basis.



	Three Months Ended March 31,
(Dollars in thousands)	2018			2017
Gross realized gains	$	2		$	1,285
Gross realized losses	(347		)	—
OTTI losses	—			—
Net realized gains (losses)	$	(345	)	$	1,285

At March 31, 2018 and December 31, 2017, investment securities available-for-sale with carrying values of $262.74 million and $289.05 million, respectively, were pledged as collateral for security repurchase agreements and for other purposes.