Investments

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



	As of December 31, 2015
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available for sale:
Mortgage-backed securities	$	196,402	$	1,370	$	(2,381	)	$	195,391

	As of December 31, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available for sale:
Mortgage-backed securities	$	167,740	$	2,686	$	(1,492	)	$	168,934

The following table summarizes the amount of gross unrealized losses for our mortgage-backed securities 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, 2015:
Mortgage-backed securities	$	(827	)	$	73,802	$	(1,554	)	$	39,271	$	(2,381	)	$	113,073

As of December 31, 2014:
Mortgage-backed securities	$	(27	)	$	12,147	$	(1,465	)	$	41,462	$	(1,492	)	$	53,609

Our investment portfolio is comprised of mortgage-backed securities issued by Ginnie Mae, Fannie Mae and Freddie Mac, with amortized costs of $93.6 million, $78.7 million, and $24.1 million, respectively, at December 31, 2015. We own these securities to meet our requirements under the Community Reinvestment Act. As of December 31, 2015, there were 35 of 74 separate mortgage-backed securities with unrealized losses in our investment portfolio. Fourteen of the 35 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, 2014, there were 13 of 56 separate mortgage-backed securities with unrealized losses in our investment portfolio. Nine of the 13 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.

As of December 31, 2015, 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	$	284	$	307
2039	7,539		8,054
2042	22,336		21,282
2043	59,961		60,165
2044	47,833		47,815
2045	58,449		57,768
Total	$	196,402	$	195,391

In October 2013, we sold our asset-backed security portfolio for a gain of $63.8 million. We no longer hold asset-backed securities in our investment portfolio.

The mortgage-backed securities have been pledged to the FRB as collateral against any advances and accrued interest under the Primary Credit program or any other program sponsored by the FRB. We had $188.3 million and $160.9 million par value of mortgage-backed securities pledged to this borrowing facility at December 31, 2015 and 2014, respectively, as discussed further in Note 9, “Borrowings.”