INVESTMENTS

The amortized cost and fair value of investment securities classified as available for sale and held to maturity at March 31, 2015 and December 31, 2014, are as follows:



	March 31, 2015
(Dollars in thousands)	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities available for sale
U.S. Treasury	$	2,237,002	$	9,966	$	2	$	2,246,966
Government agency	988,563		2,382		51		990,894
Mortgage-backed securities	3,785,912		27,006		5,669		3,807,249
Total investment securities available for sale	$	7,011,477	$	39,354	$	5,722	$	7,045,109

	December 31, 2014
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
U.S. Treasury	$	2,626,900	$	2,922	$	152	$	2,629,670
Government agency	908,362		702		247		908,817
Mortgage-backed securities	3,628,187		16,964		11,847		3,633,304
Municipal securities	125		1		—		126
Total investment securities available for sale	$	7,163,574	$	20,589	$	12,246	$	7,171,917

	March 31, 2015
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities held to maturity
Mortgage-backed securities	$	441	$	18	$	—	$	459

	December 31, 2014
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Mortgage-backed securities	$	518	$	26	$	—	$	544

Investments in mortgage-backed securities primarily represent securities issued by the Government National Mortgage Association, Federal National Mortgage Association and Federal Home Loan Mortgage Corporation.The following table provides the amortized cost and fair value by contractual maturity. Expected maturities will differ from contractual maturities on certain securities because borrowers and issuers may have the right to call or prepay obligations with or without prepayment penalties. Repayments of mortgage-backed securities are dependent on the repayments of the underlying loan balances.



	March 31, 2015				December 31, 2014
(Dollars in thousands)	Cost		Fair value		Cost		Fair value
Investment securities available for sale
Non-amortizing securities maturing in:
One year or less	$	504,826	$	505,182	$	447,866	$	447,992
One through five years	2,720,739		2,732,678		3,087,521		3,090,621
Mortgage-backed securities	3,785,912		3,807,249		3,628,187		3,633,304
Total investment securities available for sale	$	7,011,477	$	7,045,109	$	7,163,574	$	7,171,917
Investment securities held to maturity
Mortgage-backed securities held to maturity	$	441	$	459	$	518	$	544

For each period presented, securities gains (losses) included the following:



	Three months ended March 31
(Dollars in thousands)	2015			2014
Gross gains on sales of investment securities available for sale	$	5,135		$	—
Gross losses on sales of investment securities available for sale	(9		)	—
Total securities gains	$	5,126		$	—

The following table provides information regarding securities with unrealized losses as of March 31, 2015 and December 31, 2014.



	March 31, 2015
	Less than 12 months				12 months or more				Total
(Dollars in thousands)	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Investment securities available for sale:
U.S. Treasury	$	13,024	$	2	$	—	$	—	$	13,024	$	2
Government agency	69,660		51		—		—		69,660		51
Mortgage-backed securities	562,616		1,645		317,685		4,024		880,301		5,669
Total	$	645,300	$	1,698	$	317,685	$	4,024	$	962,985	$	5,722

	December 31, 2014
	Less than 12 months				12 months or more				Total
	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Investment securities available for sale:
U.S. Treasury	$	338,612	$	151	$	1,015	$	1	$	339,627	$	152
Government agency	261,288		247		—		—		261,288		247
Mortgage-backed securities	573,374		1,805		831,405		10,042		1,404,779		11,847
Total	$	1,173,274	$	2,203	$	832,420	$	10,043	$	2,005,694	$	12,246

Investment securities with an aggregate fair value of $317.7 million and $832.4 million had continuous unrealized losses for more than 12 months as of March 31, 2015 and December 31, 2014, with an aggregate unrealized loss of $4.0 million and $10.0 million, respectively. As of March 31, 2015, all 38 of these investments are government sponsored enterprise-issued mortgage-backed securities. None of the unrealized losses identified as of March 31, 2015 or December 31, 2014 relate to the marketability of the securities or the issuer’s ability to honor redemption obligations. For all periods presented, BancShares had the ability and intent to retain these securities for a period of time sufficient to recover all unrealized losses. Therefore, none of the securities were deemed to be other than temporarily impaired.

Investment securities having an aggregate carrying value of $4.45 billion at March 31, 2015 and $4.37 billion at December 31, 2014 were pledged as collateral to secure public funds on deposit and certain short-term borrowings, and for other purposes as required by law.