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, 2016
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	107,312	$	348	$	—		$	107,660
Obligations of states and political subdivisions	36,486		630		(485		)	36,631
Agency mortgage-backed securities	319,345		1,101		(3,940		)	316,506
Total securities available for sale	$	463,143	$	2,079	$	(4,425	)	$	460,797

Held to maturity securities:
Obligations of states and political subdivisions	$	14,759	$	11	$	(242	)	$	14,528
Agency mortgage-backed securities	65,704		45		(638		)	65,111
Total securities held to maturity	$	80,463	$	56	$	(880	)	$	79,639

	December 31, 2015
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	98,699	$	309	$	—		$	99,008
Obligations of states and political subdivisions	40,700		1,343		(342		)	41,701
Agency mortgage-backed securities	311,516		2,046		(2,501		)	311,061
Total securities available for sale	$	450,915	$	3,698	$	(2,843	)	$	451,770

Held to maturity securities:
Obligations of states and political subdivisions	$	14,831	$	63	$	(50	)	$	14,844
Agency mortgage-backed securities	28,883		—		(286		)	28,597
Total securities held to maturity	$	43,714	$	63	$	(336	)	$	43,441

At December 31, 2016, and 2015, 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. Available for sale securities having a fair value of $407.3 million and $334.4 million at December 31, 2016, and December 31, 2015, 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, 2016, 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 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	$	52,457	$	52,574	$	658	$	655
Due after one year through five years	76,529		77,254		5,609		5,559
Due after five years through ten years	11,912		11,842		7,380		7,241
Due after ten years	2,900		2,620		1,112		1,073
Mortgage-backed securities	319,345		316,507		65,704		65,111
	$	463,143	$	460,797	$	80,463	$	79,639

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



	December 31, 2016
	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	21,361		408		3,553		320		24,914		728
Agency mortgage-backed securities	267,734		4,084		12,883		493		280,617		4,577
	$	289,095	$	4,492	$	16,436	$	813	$	305,531	$	5,305

	December 31, 2015
	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	2,199		12		9,395		380		11,594		392
Agency mortgage-backed securities	189,229		2,050		21,020		737		210,249		2,787
	$	191,428	$	2,062	$	30,415	$	1,117	$	221,843	$	3,179

The unrealized losses at both December 31, 2016, and 2015, 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, 2016 and 2015, 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)	2016		2015			2014
Gross gains realized	$	86	$	63		$	—
Gross losses realized	—		(40		)	—
Proceeds from sales	2,493		41,069			—

Other Investments, At Cost

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 $4.4 million 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 include the Company's investment in unconsolidated trusts used to issue preferred securities to third parties (see Note 11 – Subordinated Debentures) and various private equity investments.