Investment Securities (Tables)

9 Months Ended

Sep. 30, 2018

Investments, Debt and Equity Securities [Abstract]

Summary of Amortized Cost and Estimated Fair Value of Investment Securities

The amortized cost and estimated fair value of investment securities are summarized below. The majority of securities held are available-for-sale securities with fair value based on quoted prices for similar assets in active markets or quoted prices for identical assets in markets that are not active. Estimated fair values were obtained from an independent pricing service based upon market quotes.

	September 30, 2018
	Amortized Cost		Gross Unrealized Holding Gain		Gross Unrealized Holding Loss			Fair Value		Total Percent
	(Dollars in thousands)
Investment securities available-for-sale:
Residential mortgage-backed securities	$	1,570,072	$	1,014	$	(38,208	)	$	1,532,878		84.87	%
CMO/REMIC - residential		229,832		152		(6,167	)		223,817		12.39	%
Municipal bonds		50,022		308		(1,591	)		48,739		2.70	%
Other securities		797		-		-			797		0.04	%
Total available-for-sale securities	$	1,850,723	$	1,474	$	(45,966	)	$	1,806,231		100.00	%
Investment securities held-to-maturity:
Government agency/GSE	$	144,871	$	-	$	(5,129	)	$	139,742		19.09	%
Residential mortgage-backed securities		158,769		-		(5,502	)		153,267		20.92	%
CMO		216,980		-		(13,960	)		203,020		28.58	%
Municipal bonds		238,409		225		(7,908	)		230,726		31.41	%
Total held-to-maturity securities	$	759,029	$	225	$	(32,499)		$	726,755		100.00	%

	December 31, 2017
	Amortized Cost		Gross Unrealized Holding Gain		Gross Unrealized Holding Loss			Fair Value		Total Percent
	(Dollars in thousands)
Investment securities available-for-sale:
Residential mortgage-backed securities	$	1,747,780	$	11,231	$	(8,102	)	$	1,750,909		84.14	%
CMO/REMIC-residential		274,634		1,277		(2,082	)		273,829		13.16	%
Municipal bonds		54,966		774		(244	)		55,496		2.66	%
Other securities		751		-		-			751		0.04	%
Total available-for-sale securities	$	2,078,131	$	13,282	$	(10,428	)	$	2,080,985		100.00	%
Investment securities held-to-maturity:
Government agency/GSE	$	159,716	$	854	$	(2,134	)	$	158,436		19.25	%
Residential mortgage-backed securities		176,427		667		(382	)		176,712		21.26	%
CMO		225,072		-		(8,641	)		216,431		27.12	%
Municipal bonds		268,675		2,751		(3,790	)		267,636		32.37	%
Total held-to-maturity securities	$	829,890	$	4,272	$	(14,947)		$	819,215		100.00	%

Summary of Interest Income Earned on Investment Securities

The following table provides information about the amount of interest income earned on investment securities which is fully taxable and which is exempt from regular federal income tax.

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
	2018		2017		2018		2017
	(Dollars in thousands)
Investment securities available-for-sale:
Taxable	$	11,126	$	11,767	$	33,861	$	36,113
Tax-advantaged		395		473		1,225		1,774
Total interest income from available-for-sale securities		11,521		12,240		35,086		37,887
Investment securities held-to-maturity:
Taxable		2,961		3,111		8,887		9,591
Tax-advantaged		1,705		2,073		5,351		6,423
Total interest income from held-to-maturity securities		4,666		5,184		14,238		16,014
Total interest income from investment securities	$	16,187	$	17,424	$	49,324	$	53,901

Summary of Continuous Unrealized Loss Position of Securities

The tables below show the Company’s investment securities’ gross unrealized losses and fair value by investment category and length of time that individual securities have been in a continuous unrealized loss position at September 30, 2018 and December 31, 2017. Management has reviewed individual securities to determine whether a decline in fair value below the amortized cost basis is other-than-temporary. The unrealized losses on these securities were primarily attributed to changes in interest rates. The issuers of these securities have not, to our knowledge, evidenced any cause for default on these securities. These securities have fluctuated in value since their purchase dates as market rates have fluctuated. However, we have the ability to hold and do not have the intent to sell these securities. As such, management does not deem these securities to be Other-Than-Temporarily-Impaired (“OTTI”).

	September 30, 2018
	Less Than 12 Months					12 Months or Longer					Total
	Fair Value		Gross Unrealized Holding Losses			Fair Value		Gross Unrealized Holding Losses			Fair Value		Gross Unrealized Holding Losses
	(Dollars in thousands)
Investment securities available-for-sale:
Residential mortgage-backed securities	$	1,193,435	$	(24,475	)	$	287,707	$	(13,733	)	$	1,481,142	$	(38,208	)
CMO/REMIC - residential		139,064		(3,053	)		60,925		(3,114	)		199,989		(6,167	)
Municipal bonds		11,257		(389	)		12,987		(1,202	)		24,244		(1,591	)
Total available-for-sale securities	$	1,343,756	$	(27,917	)	$	361,619	$	(18,049	)	$	1,705,375	$	(45,966	)
Investment securities held-to-maturity:
Government agency/GSE	$	99,203	$	(2,326	)	$	40,539	$	(2,803	)	$	139,742	$	(5,129	)
Residential mortgage-backed securities		101,083		(3,206	)		52,184		(2,296	)		153,267		(5,502	)
CMO		-		-			203,020		(13,960	)		203,020		(13,960	)
Municipal bonds		116,918		(2,143	)		67,284		(5,765	)		184,202		(7,908	)
Total held-to-maturity securities	$	317,204	$	(7,675	)	$	363,027	$	(24,824	)	$	680,231	$	(32,499	)
	December 31, 2017
	Less Than 12 Months					12 Months or Longer					Total
	Fair Value		Gross Unrealized Holding Losses			Fair Value		Gross Unrealized Holding Losses			Fair Value		Gross Unrealized Holding Losses
	(Dollars in thousands)
Investment securities available-for-sale:
Residential mortgage-backed securities	$	414,091	$	(1,828	)	$	303,746	$	(6,274	)	$	717,837	$	(8,102	)
CMO/REMIC - residential		95,137		(487	)		71,223		(1,595	)		166,360		(2,082	)
Municipal bonds		946		(4	)		13,956		(240	)		14,902		(244	)
Total available-for-sale securities	$	510,174	$	(2,319	)	$	388,925	$	(8,109	)	$	899,099	$	(10,428	)
Investment securities held-to-maturity:
Government agency/GSE	$	18,950	$	(27	)	$	43,495	$	(2,107	)	$	62,445	$	(2,134	)
Residential mortgage-backed securities		51,297		(188	)		55,306		(194	)		106,603		(382	)
CMO		-		-			216,431		(8,641	)		216,431		(8,641	)
Municipal bonds		32,069		(492	)		66,217		(3,298	)		98,286		(3,790	)
Total held-to-maturity securities	$	102,316	$	(707	)	$	381,449	$	(14,240	)	$	483,765	$	(14,947	)

Summary of Amortized Cost and Fair Value of Debt Securities by Contractual Maturity

Mortgage-backed and CMO/REMIC securities are included in maturity categories based upon estimated average lives which incorporate estimated prepayment speeds.

	September 30, 2018
	Available-for-sale				Held-to-maturity
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(Dollars in thousands)
Due in one year or less	$	19,806	$	19,964	$	-	$	-
Due after one year through five years		1,676,348		1,637,053		315,036		298,729
Due after five years through ten years		113,539		109,910		172,281		167,824
Due after ten years		41,030		39,304		271,712		260,202
Total investment securities	$	1,850,723	$	1,806,231	$	759,029	$	726,755