INVESTMENTS

The following table presents the amortized cost, gross unrealized gains and losses and fair value of securities available for sale and held to maturity:



	December 31, 2018
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	99,926	$	—	$	(1,428	)	$	98,498
Obligations of states and political subdivisions	26,566		327		(83		)	26,810
Agency mortgage-backed securities	596,825		1,160		(11,849		)	586,136
U.S. Treasury Bills	9,962		—		(37		)	9,925
Total securities available for sale	$	733,279	$	1,487	$	(13,397	)	$	721,369

Held to maturity securities:
Obligations of states and political subdivisions	$	12,506	$	16	$	(114	)	$	12,408
Agency mortgage-backed securities	53,173		—		(1,647		)	51,526
Total securities held to maturity	$	65,679	$	16	$	(1,761	)	$	63,934

	December 31, 2017
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	99,878	$	6	$	(660	)	$	99,224
Obligations of states and political subdivisions	34,181		674		(213		)	34,642
Agency mortgage-backed securities	513,082		727		(6,293		)	507,516
Total securities available for sale	$	647,141	$	1,407	$	(7,166	)	$	641,382

Held to maturity securities:
Obligations of states and political subdivisions	$	14,031	$	69	$	(46	)	$	14,054
Agency mortgage-backed securities	59,718		16		(330		)	59,404
Total securities held to maturity	$	73,749	$	85	$	(376	)	$	73,458

At December 31, 2018, and 2017, there were no holdings of securities of any one issuer in an amount greater than 10% of shareholders’ equity, other than the U.S. Government agencies and sponsored enterprises. The agency mortgage-backed securities are all issued by U.S. Government-sponsored enterprises. Securities having a fair value of $433.7 million and $500.0 million at December 31, 2018, and December 31, 2017, respectively, were pledged as collateral to secure deposits of public institutions and for other purposes as required by law or contract provisions.

The amortized cost and estimated fair value of debt securities at December 31, 2018, by contractual maturity, are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. The weighted average life of the agency mortgage-backed securities is approximately 4 years.



	Available for sale				Held to maturity
(in thousands)	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Due in one year or less	$	22,357	$	22,213	$	—	$	—
Due after one year through five years	100,084		98,876		2,080		2,063
Due after five years through ten years	11,881		12,038		10,426		10,345
Due after ten years	2,132		2,106		—		—
Agency mortgage-backed securities	596,825		586,136		53,173		51,526
	$	733,279	$	721,369	$	65,679	$	63,934

The following table represents a summary of investment securities that had an unrealized loss:



	December 31, 2018
	Less than 12 months				12 months or more				Total
(in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Obligations of U.S. Government-sponsored enterprises	$	19,622	$	322	$	78,876	$	1,106	$	98,498	$	1,428
Obligations of states and political subdivisions	3,102		15		14,156		182		17,258		197
Agency mortgage-backed securities	87,357		2,211		389,770		11,285		477,127		13,496
U.S. Treasury Bills	—		—		9,925		37		9,925		37
	$	110,081	$	2,548	$	492,727	$	12,610	$	602,808	$	15,158

	December 31, 2017
	Less than 12 months				12 months or more				Total
(in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Obligations of states and political subdivisions	$	13,951	$	259	$	—	$	—	$	13,951	$	259
Agency mortgage-backed securities	469,655		6,034		12,229		589		481,884		6,623
	$	572,915	$	6,953	$	12,229	$	589	$	585,144	$	7,542

The unrealized losses at both December 31, 2018, and 2017, were primarily attributable to changes in market interest rates since the securities were purchased. Management systematically evaluates investment securities for other-than-temporary declines in fair value on a quarterly basis. This analysis requires management to consider various factors, which include among other considerations (1) the present value of the cash flows expected to be collected compared to the amortized cost of the security, (2) duration and magnitude of the decline in value, (3) the financial condition of the issuer or issuers, (4) structure of the security, and (5) the intent to sell the security or whether it is more likely than not that the Company would be required to sell the security before its anticipated recovery in market value. At December 31, 2018 and 2017, management performed its quarterly analysis of all securities with an unrealized loss and concluded no individual securities were other-than-temporarily impaired.

The gross gains and losses realized from sales of available for sale investment securities were as follows:



	December 31,
(in thousands)	2018		2017		2016
Gross gains realized	$	9	$	22	$	86
Gross losses realized	—		—		—
Proceeds from sales	1,451		144,076		2,493

Other Investments, At Cost

At both December 31, 2018, and 2017, other investments, at cost, totaled $26.7 million. As a member of the FHLB system administered by the Federal Housing Finance Agency, the Bank is required to maintain a minimum investment in capital stock with the FHLB Des Moines consisting of membership stock and activity-based stock. The FHLB capital stock of $9.2 million, and $12.9 million at December 31, 2018, and 2017, respectively, is recorded at cost, which represents redemption value, and is included in other investments in the consolidated balance sheets. The remaining amounts in other investments primarily include various investments in SBICs and the Company’s investment in unconsolidated trusts used to issue preferred securities to third parties (see Note 10 – Subordinated Debentures).