Investments

The amortized cost and fair value of securities available for sale are as follows:



	December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available for sale:
Mortgage-backed securities	$	227,607	$	650	$	(3,210	)	$	225,047
Utah Housing Corporation bonds	20,000		—		(959		)	19,041
Total	$	247,607	$	650	$	(4,169	)	$	244,088

	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available for sale:
Mortgage-backed securities	$	196,406	$	929	$	(3,042	)	$	194,293
Utah Housing Corporation bonds	15,000		—		(690		)	14,310
Total	$	211,406	$	929	$	(3,732	)	$	208,603

The following table summarizes the amount of gross unrealized losses for our mortgage-backed securities and Utah Housing Corporation bonds and the estimated fair value by length of time the securities have been in an unrealized loss position:



	Less than 12 months					12 months or more					Total
	Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value
As of December 31, 2017:
Mortgage-backed securities	$	(772	)	$	77,356	$	(2,438	)	$	110,500	$	(3,210	)	$	187,856
Utah Housing Corporation bonds	(77		)	4,923		(882		)	14,118		(959		)	19,041
Total	$	(849	)	$	82,279	$	(3,320	)	$	124,618	$	(4,169	)	$	206,897

As of December 31, 2016:
Mortgage-backed securities	$	(2,423	)	$	129,549	$	(619	)	$	10,885	$	(3,042	)	$	140,434
Utah Housing Corporation bonds	(690		)	14,310		—			—		(690		)	14,310
Total	$	(3,113	)	$	143,859	$	(619	)	$	10,885	$	(3,732	)	$	154,744

Our investment portfolio is comprised primarily of mortgage-backed securities issued by Ginnie Mae, Fannie Mae and Freddie Mac, with amortized costs of $110.2 million, $70.8 million, and $46.6 million, respectively, at December 31, 2017. We own these securities to meet our requirements under the Community Reinvestment Act. As of December 31, 2017, there were 62 of 92 separate mortgage-backed securities with unrealized losses in our investment portfolio. As of December 31, 2017, 31 of the 62 securities in a net loss position were issued under Ginnie Mae programs that carry a full faith and credit guarantee from the U.S. Government. The remaining securities in a net loss position carry a principal and interest guarantee by Fannie Mae. As of December 31, 2016, there were 48 of 84 separate mortgage-backed securities with unrealized losses in our investment portfolio. Twenty-one of the 48 securities in a net loss position were issued by Ginnie Mae. We have the ability and the intent to hold these securities for a period of time sufficient for the market price to recover to at least the adjusted amortized cost of the security.

We also invest in Utah Housing Corporation bonds for the purpose of complying with the Community Reinvestment Act. These bonds are Aa3 rated by Moody’s Investors Service. The amortized cost of the investment on the consolidated balance sheet at December 31, 2017 was $20 million. We have the intent and ability to hold these bonds for a period of time sufficient for the market price to recover to at least the adjusted amortized cost of the security.

As of December 31, 2017, the amortized cost and fair value of securities, by contractual maturities, are summarized below. Contractual maturities versus actual maturities may differ due to the effect of prepayments.



Year of Maturity	Amortized Cost		Estimated Fair Value
2038	$	272	$	293
2039	3,406		3,606
2042	10,993		10,487
2043	37,438		37,534
2044	28,301		28,206
2045	41,082		40,484
2046	48,785		47,771
2047	77,330		75,707
Total	$	247,607	$	244,088

The mortgage-backed securities have been pledged to the FRB as collateral against any advances and accrued interest under the Primary Credit lending program sponsored by the FRB. We had $218.4 million and $188.0 million par value of mortgage-backed securities pledged to this borrowing facility at December 31, 2017 and 2016, respectively, as discussed further in Note 9, “Borrowings.”