The carrying amounts and fair values of investment securities at June 30, 2018 and December 31, 2017 are summarized as follows:



	June 30, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Fair Value
	(in thousands)
Held-to-maturity debt securities
Tax-exempt	$	280,186	$	2,080	$	(7,548	)	$	274,718

Available-for-sale debt securities
CDO	$	50	$	21,795	$	—		$	21,845
Commercial MBS issued by GSEs	109,010		49		(6,364		)	102,695
Corporate debt securities	105,036		119		(5,175		)	99,980
Private label residential MBS	856,917		35		(25,565		)	831,387
Residential MBS issued by GSEs	1,618,253		216		(58,696		)	1,559,773
Tax-exempt	493,052		5,767		(6,481		)	492,338
Trust preferred securities	32,000		—		(3,383		)	28,617
U.S. government sponsored agency securities	64,000		—		(4,093		)	59,907
U.S. treasury securities	2,496		—		(23		)	2,473
Total AFS debt securities	$	3,280,814	$	27,981	$	(109,780	)	$	3,199,015



	December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Fair Value
	(in thousands)
Held-to-maturity debt securities
Tax-exempt	$	255,050	$	4,514	$	(3,250	)	$	256,314

Available-for-sale debt securities
CDO	$	50	$	21,807	$	—		$	21,857
Commercial MBS issued by GSEs	113,069		46		(4,038		)	109,077
Corporate debt securities	105,044		261		(1,822		)	103,483
Private label residential MBS	874,261		756		(6,493		)	868,524
Residential MBS issued by GSEs	1,719,188		810		(30,703		)	1,689,295
Tax-exempt	501,988		10,893		(1,971		)	510,910
Trust preferred securities	32,000		—		(3,383		)	28,617
U.S. government sponsored agency securities	64,000		—		(2,538		)	61,462
U.S. treasury securities	2,496		—		(14		)	2,482

Available-for-sale equity securities (1)
CRA investments	51,133		—		(517		)	50,616
Preferred stock	52,172		1,160		(136		)	53,196
Total AFS securities	$	3,515,401	$	35,733	$	(51,615	)	$	3,499,519

(1)

The Company's equity securities consist of CRA investments and preferred stock. Effective January 1, 2018, the Company adopted the amendments within ASU 2016-01, "Recognition and Measurement of Financial Assets and Financial Liabilities," which requires that fair value changes in equity securities be recognized as part of non-interest income. Prior to January 1, 2018, equity securities were classified as part of AFS securities. On a prospective basis, equity securities will be reported separately.

The fair value of the Company's equity securities at June 30, 2018 totaled $143.5 million, which consisted of CRA investments of $50.8 million and preferred stock of $92.7 million. The portion of unrealized gains and losses related to equity securities still held at the reporting date is calculated as follows:



	Three Months Ended June 30, 2018			Six Months Ended June 30, 2018
	(in thousands)
Net (losses) gains on equity securities	$	(685	)	$	(1,759	)
Less: Net gains (losses) on equity securities sold	—			—
Unrealized (losses) gains on equity securities still held at the reporting date	$	(685	)	$	(1,759	)

The Company conducts an OTTI analysis on a quarterly basis. The initial indication of OTTI for both debt and equity securities is a decline in the market value below the amount recorded for an investment, and taking into account the severity and duration of the decline. Another potential indication of OTTI is a downgrade below investment grade. In determining whether an impairment is OTTI, the Company considers the length of time and the extent to which the market value has been below cost, recent events specific to the issuer, including investment downgrades by rating agencies and economic conditions of its industry, and the Company’s ability and intent to hold the investment for a period of time sufficient to allow for any anticipated recovery. For marketable equity securities, the Company also considers the issuer’s financial condition, capital strength, and near-term prospects.

For debt securities, for the purpose of an OTTI analysis, the Company also considers the cause of the price decline (general level of interest rates, credit spreads, and industry and issuer-specific factors), the issuer’s financial condition, near-term prospects, and current ability to make future payments in a timely manner, as well as the issuer’s ability to service debt, and any change in agencies’ ratings at the evaluation date from the acquisition date and any likely imminent action.

The Company has reviewed securities for which there is an unrealized loss in accordance with its accounting policy for OTTI described above and determined that there are no impairment charges for the three and six months ended June 30, 2018 and 2017. The Company does not consider any securities to be other-than-temporarily impaired as of June 30, 2018 and December 31, 2017. No assurance can be made that OTTI will not occur in future periods.

Information pertaining to securities with gross unrealized losses at June 30, 2018 and December 31, 2017, aggregated by investment category and length of time that individual securities have been in a continuous loss position follows:



	June 30, 2018
	Less Than Twelve Months				More Than Twelve Months				Total
	Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value
	(in thousands)
Held-to-maturity debt securities
Tax-exempt	$	7,548	$	121,943	$	—	$	—	$	7,548	$	121,943

Available-for-sale debt securities
Commercial MBS issued by GSEs	$	325	$	11,688	$	6,039	$	89,172	$	6,364	$	100,860
Corporate debt securities	2,825		57,176		2,350		37,650		5,175		94,826
Private label residential MBS	16,820		601,595		8,745		200,707		25,565		802,302
Residential MBS issued by GSEs	26,183		923,747		32,513		616,712		58,696		1,540,459
Tax-exempt	2,762		155,941		3,719		67,341		6,481		223,282
Trust preferred securities	—		—		3,383		28,617		3,383		28,617
U.S. government sponsored agency securities	131		4,869		3,962		55,038		4,093		59,907
U.S. treasury securities	23		2,473		—		—		23		2,473
Total AFS securities	$	49,069	$	1,757,489	$	60,711	$	1,095,237	$	109,780	$	2,852,726



	December 31, 2017
	Less Than Twelve Months				More Than Twelve Months				Total
	Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value
	(in thousands)
Held-to-maturity debt securities
Tax-exempt	$	3,250	$	107,921	$	—	$	—	$	3,250	$	107,921

Available-for-sale debt securities
Commercial MBS issued by GSEs	$	161	$	13,565	$	3,877	$	93,641	$	4,038	$	107,206
Corporate debt securities	1,398		78,602		424		19,576		1,822		98,178
Private label residential MBS	3,115		480,885		3,378		188,710		6,493		669,595
Residential MBS issued by GSEs	13,875		999,478		16,828		523,270		30,703		1,522,748
Tax-exempt	17		6,159		1,954		69,674		1,971		75,833
Trust preferred securities	—		—		3,383		28,617		3,383		28,617
U.S. government sponsored agency securities	14		4,986		2,524		56,476		2,538		61,462
U.S. treasury securities	14		2,482		—		—		14		2,482

Available-for-sale equity securities
CRA investments	—		—		517		50,616		517		50,616
Preferred stock	136		7,357		—		—		136		7,357
Total AFS securities	$	18,730	$	1,593,514	$	32,885	$	1,030,580	$	51,615	$	2,624,094

At June 30, 2018 and December 31, 2017, the Company’s unrealized losses relate primarily to market interest rate increases since the securities' original purchase date. The total number of securities in an unrealized loss position at June 30, 2018 is 391, compared to 302 at December 31, 2017. In analyzing an issuer’s financial condition, management considers whether the securities are issued by the federal government or its agencies, whether downgrades by bond rating agencies have occurred, and industry analysis reports. Since material downgrades have not occurred and management does not intend to sell the debt securities in an unrealized loss position in the foreseeable future, none of the securities described in the above table or in this paragraph are deemed to be OTTI.

The amortized cost and fair value of securities as of June 30, 2018, by contractual maturities, are shown below. MBS are shown separately as individual MBS are comprised of pools of loans with varying maturities. Therefore, these securities are listed separately in the maturity summary.



	June 30, 2018
	Amortized Cost		Estimated Fair Value
	(in thousands)
Held-to-maturity
Due in one year or less	$	1,200	$	1,241
After one year through five years	24,818		24,608
After ten years	254,168		248,869
Total HTM securities	$	280,186	$	274,718

Available-for-sale
Due in one year or less	$	4,015	$	4,016
After one year through five years	15,904		16,144
After five years through ten years	252,097		244,948
After ten years	424,618		440,054
Mortgage-backed securities	2,584,180		2,493,853
Total AFS securities	$	3,280,814	$	3,199,015

The following tables summarize the carrying amount of the Company’s investment ratings position as of June 30, 2018 and December 31, 2017:



	June 30, 2018
	AAA		Split-rated AAA/AA+		AA+ to AA-		A+ to A-		BBB+ to BBB-		BB+ and below		Unrated		Totals
	(in thousands)
Held-to-maturity debt securities
Tax-exempt	$	—	$	—	$	—	$	—	$	—	$	—	$	280,186	$	280,186

Available-for-sale debt securities
CDO	$	—	$	—	$	—	$	—	$	—	$	21,845	$	—	$	21,845
Commercial MBS issued by GSEs	—		102,695		—		—		—		—		—		102,695
Corporate debt securities	—		—		—		71,780		28,200		—		—		99,980
Private label residential MBS	791,921		—		36,359		464		1,092		1,551		—		831,387
Residential MBS issued by GSEs	—		1,559,773		—		—		—		—		—		1,559,773
Tax-exempt	62,616		24,515		222,071		179,682		—		—		3,454		492,338
Trust preferred securities	—		—		—		—		28,617		—		—		28,617
U.S. government sponsored agency securities	—		59,907		—		—		—		—		—		59,907
U.S. treasury securities	—		2,473		—		—		—		—		—		2,473
Total AFS securities (1)	$	854,537	$	1,749,363	$	258,430	$	251,926	$	57,909	$	23,396	$	3,454	$	3,199,015

Equity securities
CRA investments	$	—	$	25,026	$	—	$	—	$	—	$	—	$	25,767	$	50,793
Preferred stock	—		—		—		9,875		64,073		3,983		14,766		92,697
Total equity securities (1)	$	—	$	25,026	$	—	$	9,875	$	64,073	$	3,983	$	40,533	$	143,490


(1)	Where ratings differ, the Company uses an average of the available ratings by major credit agencies.



	December 31, 2017
	AAA		Split-rated AAA/AA+		AA+ to AA-		A+ to A-		BBB+ to BBB-		BB+ and below		Unrated		Totals
	(in thousands)
Held-to-maturity debt securities
Tax-exempt	$	—	$	—	$	—	$	—	$	—	$	—	$	255,050	$	255,050

Available-for-sale debt securities
CDO	$	—	$	—	$	—	$	—	$	—	$	21,857	$	—	$	21,857
Commercial MBS issued by GSEs	—		109,077		—		—		—		—		—		109,077
Corporate debt securities	—		—		—		74,293		29,190		—		—		103,483
Private label residential MBS	809,242		—		55,161		1,350		931		1,840		—		868,524
Residential MBS issued by GSEs	—		1,689,295		—		—		—		—		—		1,689,295
Tax-exempt	64,893		25,280		249,200		167,994		—		—		3,543		510,910
Trust preferred securities	—		—		—		—		28,617		—		—		28,617
U.S. government sponsored agency securities	—		61,462		—		—		—		—		—		61,462
U.S. treasury securities	—		2,482		—		—		—		—		—		2,482

Available-for-sale equity securities
CRA investments	—		25,349		—		—		—		—		25,267		50,616
Preferred stock	—		—		—		10,388		23,822		4,104		14,882		53,196
Total AFS securities (1)	$	874,135	$	1,912,945	$	304,361	$	254,025	$	82,560	$	27,801	$	43,692	$	3,499,519


(1)	Where ratings differ, the Company uses an average of the available ratings by major credit agencies.

Securities with carrying amounts of approximately $724.4 million and $913.7 million at June 30, 2018 and December 31, 2017, respectively, were pledged for various purposes as required or permitted by law.

The following table presents gross gains and losses on sales of investment securities:



	Three Months Ended June 30,					Six Months Ended June 30,
	2018		2017			2018		2017
	(in thousands)
Gross gains	$	—	$	78		$	—	$	713
Gross losses	—		(125		)	—		(125		)
Net gains on sales of investment securities	$	—	$	(47	)	$	—	$	588