Investment Securities (Tables)

3 Months Ended

Mar. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Schedule of amortized cost and estimated fair value of securities

The amortized cost and estimated fair value of securities were as follows:

	March 31, 2020
	Amortized  Cost		Gross Unrealized Gain		Gross Unrealized Loss			Estimated Fair Value
	(Dollars in thousands)
Investment securities available-for-sale:
U.S. Treasury	$	30,179	$	2,654	$	—		$	32,833
Agency	228,715		19,350		(299		)	247,766
Corporate	174,161		2,658		(786		)	176,033
Municipal bonds	391,992		15,602		(497		)	407,097
Collateralized mortgage obligations	9,346		311		(1		)	9,656
Mortgage-backed securities	441,156		23,220		—			464,376
Total investment securities available-for-sale	1,275,549		63,795		(1,583		)	1,337,761
Investment securities held-to-maturity:
Mortgage-backed securities	32,865		1,685		—			34,550
Other	1,688		—		—			1,688
Total investment securities held-to-maturity	34,553		1,685		—			36,238
Total investment securities	$	1,310,102	$	65,480	$	(1,583	)	$	1,373,999

	December 31, 2019
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Estimated Fair Value
	(Dollars in thousands)
Investment securities available-for-sale:
U.S. Treasury	$	60,457	$	3,137	$	(39	)	$	63,555
Agency	240,348		7,686		(1,676		)	246,358
Corporate	149,150		2,217		(14		)	151,353
Municipal bonds	384,032		13,450		(184		)	397,298
Collateralized mortgage obligations	9,869		123		(8		)	9,984
Mortgage-backed securities	494,404		7,603		(2,171		)	499,836
Total investment securities available-for-sale	1,338,260		34,216		(4,092		)	1,368,384
Investment securities held-to-maturity:
Mortgage-backed securities	36,114		922		—			37,036
Other	1,724		—		—			1,724
Total investment securities held-to-maturity	37,838		922		—			38,760
Total investment securities	$	1,376,098	$	35,138	$	(4,092	)	$	1,407,144

Schedule of number, fair value and gross unrealized holding losses of the Company's investment securities by investment category and length of time that the securities have been in a continuous loss position

The table below shows the number, fair value and gross unrealized holding losses of the Company’s investment securities by investment category and length of time that the securities have been in a continuous loss position.

	March 31, 2020
	Less than 12 Months					12 Months or Longer						Total
	Number	Fair Value		Gross Unrealized Losses		Number	Fair Value		Gross Unrealized Losses			Number	Fair Value		Gross Unrealized Losses
	(Dollars in thousands)
Investment securities available-for-sale:
U.S. Treasury	—	$	—	$	—	—	$	—	$	—		—	$	—	$	—
Agency	—	—		—		9	12,166		(299		)	9	12,166		(299		)
Corporate	—	—		—		8	47,012		(786		)	8	47,012		(786		)
Municipal bonds	—	—		—		5	19,663		(497		)	5	19,663		(497		)
Collateralized mortgage obligations	—	—		—		1	565		(1		)	1	565		(1		)
Mortgage-backed securities.	—	—		—		—	—		—			—	—		—
Total investment securities available-for-sale	—	—		—		23	79,406		(1,583		)	23	79,406		(1,583		)
Investment securities held-to-maturity:
Mortgage-backed securities: residential	—	—		—		—	—		—			—	—		—
Other	—	—		—		—	—		—			—	—		—
Total investment securities held-to-maturity	—	—		—		—	—		—			—	—		—
Total investment securities	—	$	—	$	—	23	$	79,406	$	(1,583	)	23	$	79,406	$	(1,583	)

	December 31, 2019
	Less than 12 Months						12 Months or Longer						Total
	Number	Fair Value		Gross Unrealized Losses			Number	Fair Value		Gross Unrealized Losses			Number	Fair Value		Gross Unrealized Losses
	(Dollars in thousands)
Investment securities available-for-sale:
U.S. Treasury	1	$	10,194	$	(39	)	—	$	—	$	—		1	$	10,194	$	(39	)
Agency	13	102,874		(1,340		)	9	13,514		(336		)	22	116,388		(1,676		)
Corporate	1	1,017		(14		)	—	—		—			1	1,017		(14		)
Municipal bonds	12	30,541		(184		)	—	—		—			12	30,541		(184		)
Collateralized mortgage obligations	—	—		—			1	603		(8		)	1	603		(8		)
Mortgage-backed securities.	18	130,014		(1,681		)	11	26,886		(490		)	29	156,900		(2,171		)
Total investment securities available-for-sale	45	274,640		(3,258		)	21	41,003		(834		)	66	315,643		(4,092		)
Investment securities held-to-maturity:
Mortgage-backed securities	—	—		—			—	—		—			—	—		—
Total investment securities held-to-maturity	—	—		—			—	—		—			—	—		—
Total investment securities	45	$	274,640	$	(3,258	)	21	$	41,003	$	(834	)	66	$	315,643	$	(4,092	)

Schedule of amortized cost and estimated fair value of investment securities available for sale by contractual maturity

The amortized cost and estimated fair value of investment securities at March 31, 2020, by contractual maturity are shown in the table below.

	Due in One Year or Less				Due after One Year through Five Years				Due after Five Years through Ten Years				Due after Ten Years				Total
	Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(Dollars in thousands)
Investment securities available-for-sale:
U.S. Treasury	$	—	$	—	$	20,155	$	21,555	$	10,024	$	11,278	$	—	$	—	$	30,179	$	32,833
Agency	1,000		1,019		40,613		43,765		155,152		166,661		31,950		36,321		228,715		247,766
Corporate	—		—		—		—		174,161		176,033		—		—		174,161		176,033
Municipal bonds	9,920		9,607		1,848		1,952		30,979		32,648		349,245		362,890		391,992		407,097
Collateralized mortgage obligations	—		—		—		—		566		565		8,780		9,091		9,346		9,656
Mortgage-backed securities	—		—		2,236		2,436		196,338		208,414		242,582		253,526		441,156		464,376
Total investment securities available-for-sale	10,920		10,626		64,852		69,708		567,220		595,599		632,557		661,828		1,275,549		1,337,761
Investment securities held-to-maturity:
Mortgage-backed securities	—		—		—		—		—		—		32,865		34,550		32,865		34,550
Other	—		—		—		—		—		—		1,688		1,688		1,688		1,688
Total investment securities held-to-maturity	—		—		—		—		—		—		34,553		36,238		34,553		36,238
Total investment securities	$	10,920	$	10,626	$	64,852	$	69,708	$	567,220	$	595,599	$	667,110	$	698,066	$	1,310,102	$	1,373,999

Schedule of Investment Securities by External Credit Rating

The following table summarizes the Company’s investment securities portfolio by Moody’s external rating equivalent and by vintage as of March 31, 2020:

	Vintage
	2020		2019		2018		2017		2016		Prior		Total
	(Dollars in thousands)
Investment securities available-for-sale
U.S. Treasury
Aaa - Aa3	$	—	$	—	$	22,091	$	10,742	$	—	$	—	$	32,833
A1 - A3	—		—		—		—		—		—		—
Baa1 - Baa3	—		—		—		—		—		—		—
Agency
Aaa - Aa3	—		30,350		111,128		9,668		16,063		68,391		235,600
A1 - A3	—		—		—		—		—		—		—
Baa1 - Baa3	—		—		—		—		5,521		6,645		12,166
Corporate debt
Aaa - Aa3	—		—		—		—		—		—		—
A1 - A3	—		19,858		—		—		10,772		—		30,630
Baa1 - Baa3	20,015		42,353		31,435		18,080		20,514		13,006		145,403
Municipal bonds
Aaa - Aa3	19,663		258,095		32,219		39,913		18,950		23,775		392,615
A1 - A3	—		—		—		—		1,800		2,270		4,070
Baa1 - Baa3	—		5,731		—		3,357		—		1,324		10,412
Collateralized mortgage obligations
Aaa - Aa3	—		—		—		—		—		9,656		9,656
A1 - A3	—		—		—		—		—		—		—
Baa1 - Baa3	—		—		—		—		—		—		—
Mortgage-backed securities
Aaa - Aa3	24,063		156,697		54,080		86,204		45,811		97,521		464,376
A1 - A3	—		—		—		—		—		—		—
Baa1 - Baa3	—		—		—		—		—		—		—
Total investment securities available-for-sale	63,741		513,084		250,953		167,964		119,431		222,588		1,337,761
Investment securities held-to-maturity
Mortgage-backed securities
Aaa - Aa3	—		—		10,332		8,104		5,396		9,033		32,865
A1 - A3	—		—		—		—		—		—		—
Baa1 - Baa3	—		—		—		—		—		—		—
Other
Aaa - Aa3	—		—		—		—		—		—		—
A1 - A3	—		—		—		—		—		—		—
Baa1 - Baa3	—		—		672		—		—		1,016		1,688
Total investment securities held-to-maturity	—		—		11,004		8,104		5,396		10,049		34,553
Total investment securities	$	63,741	$	513,084	$	261,957	$	176,068	$	124,827	$	232,637	$	1,372,314