Debt Securities Available-for-Sale

The following is a comparative summary of mortgage-backed and other debt securities available-for-sale at March 31, 2019, and December 31, 2018 (in thousands):



	March 31, 2019
			Gross		Gross		Estimated
	Amortized		unrealized		unrealized		fair
	cost		gains		losses		value
Mortgage-backed securities:
Pass-through certificates:
Government sponsored enterprises (GSE)	$	404,108	$	2,656	$	2,227	$	404,537
Real estate mortgage investment conduits (REMICs):
GSE	268,399		565		5,472		263,492
Non-GSE	58		—		1		57
	672,565		3,221		7,700		668,086
Other debt securities:
Municipal bonds	270		4		—		274
Corporate bonds	225,599		727		414		225,912
	225,869		731		414		226,186
Total debt securities available-for-sale	$	898,434	$	3,952	$	8,114	$	894,272



	December 31, 2018
			Gross		Gross		Estimated
	Amortized		unrealized		unrealized		fair
	cost		gains		losses		value
Mortgage-backed securities:
Pass-through certificates:
GSE	$	317,530	$	800	$	3,542	$	314,788
REMICs:
GSE	258,050		92		7,979		250,163
Non-GSE	59		—		1		58
	575,639		892		11,522		565,009
Other debt securities:
Municipal bonds	270		3		—		273
Corporate bonds	244,892		72		2,215		242,749
	245,162		75		2,215		243,022
Total debt securities available-for-sale	$	820,801	$	967	$	13,737	$	808,031

The following is a summary of the expected maturity distribution of debt securities available-for-sale, other than mortgage-backed securities, at March 31, 2019 (in thousands):



Available-for-sale	Amortized cost		Estimated fair value
Due in one year or less	$	44,901	$	44,947
Due after one year through five years	176,033		176,354
Due after five years through ten years	4,935		4,885
	$	225,869	$	226,186

Contractual maturities for mortgage-backed securities are not included above, as expected maturities on mortgage-backed securities may differ from contractual maturities as borrowers may have the right to call or prepay obligations with or without penalties.

Certain securities available-for-sale are pledged or encumbered to secure borrowings under Pledge Agreements and Repurchase Agreements and for other purposes required by law. At March 31, 2019, the fair value of debt securities available-for-sale that were pledged to secure borrowings and deposits was $484.7 million.

For the three months ended March 31, 2019, the Company had gross proceeds of $29.2 million on sales of debt securities available-for-sale, with gross realized gains of $155,000 and no gross realized losses. For the three months ended March 31, 2018, the Company had gross proceeds of $19.5 million on sales of debt securities available-for-sale, with gross realized gains of $60,000 and gross realized losses of $5,000. The Company recognized net gains of $1.1 million and $106,000, on its trading securities portfolio during the three months ended March 31, 2019, and March 31, 2018, respectively.

Gross unrealized losses on mortgage-backed and other debt securities available-for-sale, and the estimated fair value of the related securities, aggregated by security category and length of time that individual securities have been in a continuous unrealized loss position, at March 31, 2019, and December 31, 2018, were as follows (in thousands):



	March 31, 2019
	Less than 12 months				12 months or more				Total
	Unrealized		Estimated		Unrealized		Estimated		Unrealized		Estimated
	losses		fair value		losses		fair value		losses		fair value
Mortgage-backed securities:
Pass-through certificates:
GSE	$	170	$	34,164	$	2,057	$	96,411	$	2,227	$	130,575
REMICs:
GSE	8		19,136		5,464		170,787		5,472		189,923
Non-GSE					1		57		1		57
Other debt securities:
Corporate bonds	124		53,417		290		35,806		414		89,223
Total	$	302	$	106,717	$	7,812	$	303,061	$	8,114	$	409,778



	December 31, 2018
	Less than 12 months				12 months or more				Total
	Unrealized		Estimated		Unrealized		Estimated		Unrealized		Estimated
	losses		fair value		losses		fair value		losses		fair value
Mortgage-backed securities:
Pass-through certificates:
GSE	$	404	$	82,781	$	3,138	$	100,109	$	3,542	$	182,890
REMICs:
GSE	269		46,921		7,710		181,512		7,979		228,433
Non-GSE	—		—		1		58		1		58
Other debt securities:
Corporate bonds	1,703		173,219		512		25,675		2,215		198,894
Total	$	2,376	$	302,921	$	11,361	$	307,354	$	13,737	$	610,275

The Company held 50 pass-through mortgage-backed securities issued or guaranteed by GSEs, 45 REMIC mortgage-backed securities issued or guaranteed by GSEs, one REMIC mortgage-backed security not issued or guaranteed by a GSE, and seven corporate bonds that were in a continuous unrealized loss position of twelve months or greater at March 31, 2019. There were five pass-through mortgage-backed securities issued or guaranteed by GSEs, one REMIC mortgage-backed security issued or guaranteed by a GSE, and eight corporate bonds that were in an unrealized loss position of less than twelve months at March 31, 2019. All securities referred to above, other than one corporate security with a fair value of $5.0 million and an unrealized loss of $13,000, were rated investment grade at March 31, 2019. Management evaluated these securities and concluded that the declines in value relate to the general interest rate environment and are considered temporary. The securities cannot be prepaid in a manner that would result in the Company not receiving substantially all of its amortized cost. The Company neither has an intent to sell, nor is it more likely than not that the Company will be required to sell, the securities before the recovery of their amortized cost basis or, if necessary, maturity.

The fair values of our debt securities available-for-sale could decline in the future if the underlying performance of the collateral for the collateralized mortgage obligations or other securities deteriorates and our credit enhancement levels do not provide sufficient protections to our contractual principal and interest, which may result in other-than-temporary impairment in the future. The Company did not recognize any other-than-temporary impairment charges during the three months ended March 31, 2019, or March 31, 2018.