2. Securities

The following tables set forth the amortized cost and estimated fair value of securities available-for-sale and held-to-maturity at the dates indicated.

	At March 31, 2013
(In Thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Available-for-sale:
Residential mortgage-backed securities:
GSE (1) issuance REMICs and CMOs (2)	$	293,952	$	5,698	$	(447)	$	299,203
Non-GSE issuance REMICs and CMOs	10,118		7		(41)		10,084
GSE pass-through certificates	19,468		1,025		(2)		20,491
Total residential mortgage-backed securities	323,538		6,730		(490)		329,778
Obligations of GSEs	98,672		85		(162)		98,595
Fannie Mae stock	15		—		(14)		1
Total securities available-for-sale	$	422,225	$	6,815	$	(666)	$	428,374
Held-to-maturity:
Residential mortgage-backed securities:
GSE issuance REMICs and CMOs	$	1,622,615	$	26,039	$	(2,913)	$	1,645,741
Non-GSE issuance REMICs and CMOs	5,041		97		—		5,138
GSE pass-through certificates	209		5		(1)		213
Total residential mortgage-backed securities	1,627,865		26,141		(2,914)		1,651,092
Obligations of GSEs	80,923		134		(62)		80,995
Other	639		—		—		639
Total securities held-to-maturity	$	1,709,427	$	26,275	$	(2,976)	$	1,732,726

(1) Government-sponsored enterprise

(2) Real estate mortgage investment conduits and collateralized mortgage obligations

	At December 31, 2012
(In Thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Available-for-sale:
Residential mortgage-backed securities:
GSE issuance REMICs and CMOs	$	200,152	$	5,258	$	(583)	$	204,827
Non-GSE issuance REMICs and CMOs	11,296		9		(86)		11,219
GSE pass-through certificates	20,348		1,029		(2)		21,375
Total residential mortgage-backed securities	231,796		6,296		(671)		237,421
Obligations of GSEs	98,670		214		(5)		98,879
Fannie Mae stock	15		—		(15)		—
Total securities available-for-sale	$	330,481	$	6,510	$	(691)	$	336,300
Held-to-maturity:
Residential mortgage-backed securities:
GSE issuance REMICs and CMOs	$	1,693,437	$	27,787	$	(2,955)	$	1,718,269
Non-GSE issuance REMICs and CMOs	5,791		112		—		5,903
GSE pass-through certificates	257		6		(1)		262
Total residential mortgage-backed securities	1,699,485		27,905		(2,956)		1,724,434
Other	656		—		—		656
Total securities held-to-maturity	$	1,700,141	$	27,905	$	(2,956)	$	1,725,090

The following tables set forth the estimated fair values of securities with gross unrealized losses at the dates indicated, segregated between securities that have been in a continuous unrealized loss position for less than twelve months and those that have been in a continuous unrealized loss position for twelve months or longer at the dates indicated.

	At March 31, 2013
	Less Than Twelve Months				Twelve Months or Longer				Total
(In Thousands)	Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses
Available-for-sale:
GSE issuance REMICs and CMOs	$	23,645	$	(447)	$	—	$	—	$	23,645	$	(447)
Non-GSE issuance REMICs and CMOs	—		—		9,626		(41)		9,626		(41)
GSE pass-through certificates	55		(1)		45		(1)		100		(2)
Obligations of GSEs	64,827		(162)		—		—		64,827		(162)
Fannie Mae stock	—		—		1		(14)		1		(14)
Total temporarily impaired securities available-for-sale	$	88,527	$	(610)	$	9,672	$	(56)	$	98,199	$	(666)
Held-to-maturity:
GSE issuance REMICs and CMOs	$	430,788	$	(2,845)	$	9,212	$	(68)	$	440,000	$	(2,913)
GSE pass-through certificates	43		(1)		—		—		43		(1)
Obligations of GSEs	29,908		(62)		—		—		29,908		(62)
Total temporarily impaired securities held-to-maturity	$	460,739	$	(2,908)	$	9,212	$	(68)	$	469,951	$	(2,976)

	At December 31, 2012
	Less Than Twelve Months				Twelve Months or Longer				Total
(In Thousands)	Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses
Available-for-sale:
GSE issuance REMICs and CMOs	$	67,841	$	(583)	$	—	$	—	$	67,841	$	(583)
Non-GSE issuance REMICs and CMOs	—		—		10,709		(86)		10,709		(86)
GSE pass-through certificates	57		(1)		47		(1)		104		(2)
Obligations of GSEs	24,995		(5)		—		—		24,995		(5)
Fannie Mae stock	—		—		—		(15)		—		(15)
Total temporarily impaired securities available-for-sale	$	92,893	$	(589)	$	10,756	$	(102)	$	103,649	$	(691)
Held-to-maturity:
GSE issuance REMICs and CMOs	$	413,651	$	(2,759)	$	12,259	$	(196)	$	425,910	$	(2,955)
GSE pass-through certificates	48		(1)		—		—		48		(1)
Total temporarily impaired securities held-to-maturity	$	413,699	$	(2,760)	$	12,259	$	(196)	$	425,958	$	(2,956)

We held 42 securities which had an unrealized loss at March 31, 2013 and 41 at December 31, 2012. At March 31, 2013 and December 31, 2012, substantially all of the securities in an unrealized loss position had a fixed interest rate and the cause of the temporary impairment is directly related to the change in interest rates. In general, as interest rates rise, the fair value of fixed rate securities will decrease; as interest rates fall, the fair value of fixed rate securities will increase. During this period of historic low interest rates, securities backed by fixed rate residential mortgage loans have experienced accelerated rates of prepayments as interest rates have declined which has resulted in a decline in the estimated life of these securities and a decline in fair value. We generally view changes in fair value caused by changes in interest rates as temporary, which is consistent with our experience. None of the unrealized losses are related to credit losses. Therefore, at March 31, 2013 and December 31, 2012, the impairments are deemed temporary based on (1) the direct relationship of the decline in fair value to movements in interest rates, (2) the estimated remaining life and high credit quality of the investments and (3) the fact that we do not intend to sell these securities and it is not more likely than not that we will be required to sell these securities before their anticipated recovery of the remaining amortized cost basis and we expect to recover the entire amortized cost basis of the security.

There were no sales of securities from the available-for-sale portfolio during the three months ended March 31, 2013. During the three months ended March 31, 2012, proceeds from sales of securities from the available-for-sale portfolio totaled $54.3 million, resulting in gross realized gains totaling $2.5 million.

At March 31, 2013, available-for-sale debt securities excluding mortgage-backed securities had an amortized cost of $98.7 million, a fair value of $98.6 million and contractual maturities between 2021 and 2022. At March 31, 2013, held-to-maturity debt securities excluding mortgage-backed securities had an amortized cost and a fair value of $81.6 million and contractual maturities between 2020 and 2023. Actual maturities may differ from contractual maturities because issuers may have the right to prepay or call obligations with or without prepayment penalties.

The balance of accrued interest receivable for securities totaled $6.1 million at March 31, 2013 and $5.7 million at December 31, 2012.

At March 31, 2013, we held securities with an amortized cost of $179.6 million which are callable within one year and at various times thereafter.