INVESTMENT SECURITIES

The following table presents the amortized cost and fair value of the investment securities portfolio as of the dates indicated:



($ in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2018
Securities available-for-sale:
SBA loan pool securities	$	910	$	—	$	(22	)	$	888
U.S. government agency and U.S. government sponsored enterprise residential mortgage-backed securities	472,581		—		(33,113		)	439,468
Non-agency residential mortgage-backed securities	439		12		—			451
Non-agency commercial mortgage-backed securities	135,558		—		(2,854		)	132,704
Collateralized loan obligations	1,481,415		6,835		(1,929		)	1,486,321
Total securities available-for-sale	$	2,090,903	$	6,847	$	(37,918	)	$	2,059,832
December 31, 2017
Securities available-for-sale:
SBA loan pool securities	$	1,056	$	2	$	—		$	1,058
U.S. government agency and U.S. government sponsored enterprise residential mortgage-backed securities	492,255		10		(15,336		)	476,929
Non-agency residential mortgage-backed securities	741		16		(1		)	756
Non-agency commercial mortgage-backed securities	305,172		5,339		—			310,511
Collateralized loan obligations	1,691,455		11,129		(266		)	1,702,318
Corporate debt securities	76,714		7,183		—			83,897
Total securities available-for-sale	$	2,567,393	$	23,679	$	(15,603	)	$	2,575,469

During the three months ended June 30, 2017, the Company evaluated its securities held-to-maturity and determined that certain securities no longer adhered to the Company’s strategic focus and could be sold or reinvested to potentially improve the Company’s liquidity position or duration profile. Accordingly, the Company was no longer able to assert that it had the intent to hold these securities until maturity. As a result, the Company transferred all $740.9 million of its securities held-to-maturity to securities available-for-sale, which resulted in a pre-tax increase to accumulated other comprehensive income of $22.0 million as of June 30, 2017. Due to the transfer, the Company’s ability to assert that it has the intent and ability to hold held-to-maturity debt securities will be limited for the foreseeable future.

During the three months ended March 31, 2018, the Company completed the sale of all remaining corporate debt securities, totaling $76.8 million, to reposition its securities available-for-sale portfolio. At September 30, 2018, the Company's investment securities portfolio consisted of SBA loan pool securities, mortgage-backed securities, and collateralized loan obligations. The expected maturities of these types of securities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

At September 30, 2018 and December 31, 2017, there were no holdings of any one issuer, other than the U.S. Government and its agencies, in an amount greater than 10 percent of the Company's stockholders’ equity.

The following table presents proceeds from sales and calls of securities available-for-sale and the associated gross gains and losses realized through earnings upon the sales and calls of securities available-for-sale for the periods indicated:



	Three Months Ended September 30,				Nine Months Ended September 30,
($ in thousands)	2018		2017		2018		2017
Gross realized gains on sales and calls of securities available-for-sale	$	13	$	7,625	$	5,532	$	12,080
Gross realized losses on sales and calls of securities available-for-sale	—		—		—		—
Net realized gains on sales and calls of securities available-for-sale	$	13	$	7,625	$	5,532	$	12,080
Proceeds from sales and calls of securities available-for-sale	$	283,114	$	312,961	$	896,070	$	1,199,551

Investment securities with carrying values of $139.8 million and $564.4 million as of September 30, 2018 and December 31, 2017, respectively, were pledged to secure FHLB advances, public deposits, repurchase agreements, and for other purposes as required or permitted by law.

The following table summarizes the investment securities with unrealized losses by security type and length of time in a continuous unrealized loss position as of the dates indicated:



	Less Than 12 Months					12 Months or Longer					Total
($ in thousands)	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
September 30, 2018
Securities available-for-sale:
SBA loan pool securities	$	888	$	(22	)	$	—	$	—		$	888	$	(22	)
U.S. government agency and U.S. government sponsored enterprise residential mortgage-backed securities	$	14,964	$	(376	)	$	424,417	$	(32,737	)	$	439,381	$	(33,113	)
Non-agency residential mortgage-backed securities	78		—			44		—			122		—
Non-agency commercial mortgage-backed securities	132,703		(2,854		)	—		—			132,703		(2,854		)
Collateralized loan obligations	335,446		(1,929		)	—		—			335,446		(1,929		)
Total securities available-for-sale	$	484,079	$	(5,181	)	$	424,461	$	(32,737	)	$	908,540	$	(37,918	)
December 31, 2017
Securities available-for-sale:
U.S. government agency and U.S. government sponsored enterprise residential mortgage-backed securities	$	4,880	$	(35	)	$	470,092	$	(15,301	)	$	474,972	$	(15,336	)
Non-agency residential mortgage-backed securities	—		—			148		(1		)	148		(1		)
Collateralized loan obligations	104,334		(266		)	—		—			104,334		(266		)
Total securities available-for-sale	$	109,214	$	(301	)	$	470,240	$	(15,302	)	$	579,454	$	(15,603	)

The Company did not record other-than-temporary-impairment (OTTI) for investment securities for the three and nine months ended September 30, 2018 or 2017.

At September 30, 2018, the Company’s securities available-for-sale portfolio consisted of 151 securities, 76 of which were in an unrealized loss position. At December 31, 2017, the Company’s securities available-for-sale portfolio consisted of 191 securities, 33 of which were in an unrealized loss position.

The Company monitors its securities portfolio to ensure it has adequate credit support. The majority of unrealized losses are related to the Company's mortgage-backed securities issued by U.S government sponsored entities and agencies. The Company also considers the lowest credit rating for identification of potential OTTI for other securities. As of September 30, 2018, nearly all of the Company's non-agency mortgage-backed securities or collateralized loan obligations investment securities in an unrealized loss position received an investment grade credit rating. The decline in fair value is attributable to changes in interest rates, and not credit quality. The Company believes there was no OTTI as of September 30, 2018 and does not have the intent to sell its securities in an unrealized loss position and further believes it is not likely that it will be required to sell these securities before their anticipated recovery.