INVESTMENTS

The amortized cost and fair value of investment securities classified as available for sale and held to maturity at June 30, 2017 and December 31, 2016, are as follows:



	June 30, 2017
(Dollars in thousands)	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities available for sale
U.S. Treasury	$	1,619,225	$	—	$	3,091	$	1,616,134
Government agency	40,080		1		—		40,081
Mortgage-backed securities	4,822,517		1,951		52,226		4,772,242
Equity securities	78,753		27,106		—		105,859
Corporate bonds	54,412		331		38		54,705
Other	7,630		15		216		7,429
Total investment securities available for sale	$	6,622,617	$	29,404	$	55,571	$	6,596,450

	December 31, 2016
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
U.S. Treasury	$	1,650,675	$	579	$	935	$	1,650,319
Government agency	40,291		107		—		40,398
Mortgage-backed securities	5,259,466		2,809		86,850		5,175,425
Equity securities	71,873		11,634		—		83,507
Corporate bonds	49,367		195		—		49,562
Other	7,615		—		246		7,369
Total investment securities available for sale	$	7,079,287	$	15,324	$	88,031	$	7,006,580

	June 30, 2017
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities held to maturity
Mortgage-backed securities	$	80	$	6	$	—	$	86

	December 31, 2016
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Mortgage-backed securities	$	98	$	6	$	—	$	104

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. Investments in equity securities and corporate bonds represent positions in securities of other financial institutions. Other includes investments in trust preferred securities of financial institutions. 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. Equity securities do not have a stated maturity date.



	June 30, 2017				December 31, 2016
(Dollars in thousands)	Cost		Fair value		Cost		Fair value
Investment securities available for sale
Non-amortizing securities maturing in:
One year or less	$	549,914	$	548,822	$	842,798	$	842,947
One through five years	1,109,391		1,107,393		848,168		847,770
Five through 10 years	54,412		54,705		49,367		49,562
Over 10 years	7,630		7,429		7,615		7,369
Mortgage-backed securities	4,822,517		4,772,242		5,259,466		5,175,425
Equity securities	78,753		105,859		71,873		83,507
Total investment securities available for sale	$	6,622,617	$	6,596,450	$	7,079,287	$	7,006,580
Investment securities held to maturity
Mortgage-backed securities held to maturity	$	80	$	86	$	98	$	104

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



	Three months ended June 30						Six months ended June 30
(Dollars in thousands)	2017			2016			2017			2016
Gross gains on sales of investment securities available for sale	$	3,353		$	12,555		$	3,356		$	17,488
Gross losses on sales of investment securities available for sale	(2		)	(26		)	(29		)	(331		)
Total realized securities gains	$	3,351		$	12,529		$	3,327		$	17,157

The following table provides information regarding securities with unrealized losses as of June 30, 2017 and December 31, 2016.



	June 30, 2017
	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	$	1,616,134	$	3,091	$	—	$	—	$	1,616,134	$	3,091
Mortgage-backed securities	4,101,002		47,735		339,826		4,491		4,440,828		52,226
Corporate bonds	5,000		38		—		—		5,000		38
Other	5,299		216		—		—		5,299		216
Total	$	5,727,435	$	51,080	$	339,826	$	4,491	$	6,067,261	$	55,571

	December 31, 2016
	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	$	807,822	$	935	$	—	$	—	$	807,822	$	935
Mortgage-backed securities	4,442,700		82,161		362,351		4,689		4,805,051		86,850
Other	7,369		246		—		—		7,369		246
Total	$	5,257,891	$	83,342	$	362,351	$	4,689	$	5,620,242	$	88,031

Investment securities with an aggregate fair value of $339.8 million and $362.4 million had continuous unrealized losses for more than 12 months with a corresponding aggregate unrealized loss of $4.5 million and $4.7 million as of June 30, 2017 and December 31, 2016, respectively. As of June 30, 2017, all 52 of these investments are government sponsored enterprise-issued mortgage-backed securities. None of the unrealized losses identified as of June 30, 2017 or December 31, 2016 relate to the marketability of the securities or the issuers' ability to honor redemption obligations. Rather, the unrealized losses relate to changes in interest rates relative to when the investment securities were purchased. 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 $4.71 billion at June 30, 2017 and $4.55 billion at December 31, 2016 were pledged as collateral to secure public funds on deposit and certain short-term borrowings, and for other purposes as required by law.