(3)	SECURITIES

The following table summarizes securities held for investment and securities available for sale:

	March 31, 2018		December 31, 2017
	(Dollars in thousands)
Held for investment, at cost (fair value: $2,086 and $2,303, respectively)	$	2,079	$	2,292
Available for sale, at fair value		491,022		467,703
Total	$	493,101	$	469,995

The following table summarizes the amortized cost and estimated fair values of securities held for investment:


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
March 31, 2018	(Dollars in thousands)
Mortgage backed securities (1)	$	174	$	7	$	—		$	181
States and political subdivisions		1,405		1		(1	)		1,405
Other securities		500		—		—			500
Total	$	2,079	$	8	$	(1	)	$	2,086
December 31, 2017
Mortgage backed securities (1)	$	187	$	10	$	—		$	197
States and political subdivisions		1,605		3		(2	)		1,606
Other securities		500		—		—			500
Total	$	2,292	$	13	$	(2	)	$	2,303

The following table summarizes the amortized cost and estimated fair values of securities available for sale:


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
March 31, 2018	(Dollars in thousands)
U.S. treasuries	$	344,978	$	74	$	(3,803	)	$	341,249
U.S. federal agencies		86,172		11		(283	)		85,900
Mortgage backed securities (1)		18,114		165		(594	)		17,685
States and political subdivisions		39,654		412		(143	)		39,923
Other securities (2)		7,088		71		(894	)		6,265
Total	$	496,006	$	733	$	(5,717	)	$	491,022
December 31, 2017
U.S. treasuries	$	314,905	$	—	$	(2,103	)	$	312,802
U.S. federal agencies		89,098		82		(329	)		88,851
Mortgage backed securities (1)		18,358		204		(586	)		17,976
States and political subdivisions		41,937		554		(121	)		42,370
Other securities (2)		6,527		71		(894	)		5,704
Total	$	470,825	$	911	$	(4,033	)	$	467,703

(1)

Primarily consists of FHLMC, FNMA, GNMA and mortgage backed securities through U.S. agencies.

(2)

Primarily consists of equity securities.

The maturities of securities held for investment and available for sale are summarized in the following table using contractual maturities. Actual maturities may differ from contractual maturities due to obligations that are called or prepaid. For purposes of the maturity table, mortgage-backed securities, which are not due at a single maturity date, have been presented at their contractual maturity.

	March 31, 2018				December 31, 2017
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
	(Dollars in thousands)
Held for Investment
Contractual maturity of debt securities:
Within one year	$	1,036	$	1,036	$	1,036	$	1,034
After one year but within five years		422		422		623		627
After five years but within ten years		613		620		625		633
After ten years		8		8		8		9
Total	$	2,079	$	2,086	$	2,292	$	2,303
Available for Sale
Contractual maturity of debt securities:
Within one year	$	162,621	$	162,261	$	113,225	$	112,974
After one year but within five years		268,010		264,525		289,038		287,058
After five years but within ten years		5,616		5,819		6,222		6,500
After ten years		52,671		52,152		55,813		55,467
Total debt securities		488,918		484,757		464,298		461,999
Equity securities		7,088		6,265		6,527		5,704
Total	$	496,006	$	491,022	$	470,825	$	467,703

The following table is a summary of the Company’s book value of securities that were pledged as collateral for public funds on deposit, repurchase agreements and for other purposes as required or permitted by law:

	March 31, 2018		December 31, 2017
	(Dollars in thousands)
Book value of pledged securities	$	414,121	$	440,069