Securities (Tables)

6 Months Ended

Jun. 30, 2020

Investments, Debt and Equity Securities [Abstract]

Summary of Amortized Cost and Fair Value of Available-for-sale and Held-to-maturity Securities

The amortized cost and fair value of securities available-for-sale and held-to-maturity at June 30, 2020 and December 31, 2019 are summarized as follows (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
June 30, 2020:
Securities available-for-sale:
U.S. Treasury securities	$	72,482	$	130	$	—	$	72,612
U.S. government agency securities	74,939		1,404		32		76,311
Mortgage-backed securities	1,661,910		77,923		1,387		1,738,446
State and municipal securities	1,182,925		28,447		31,643		1,179,729
Asset-backed securities	142,504		521		2,610		140,415
Corporate notes and other	106,923		499		4,657		102,765
	$	3,241,683	$	108,924	$	40,329	$	3,310,278
Securities held-to-maturity:
State and municipal securities	$	1,048,223	$	19,387	$	6,377	$	1,061,233
	$	1,048,223	$	19,387	$	6,377	$	1,061,233
Allowance for credit losses - securities held-to-maturity	(188)
Securities held-to-maturity, net of allowance for credit losses	$	1,048,035


December 31, 2019:
Securities available-for-sale:
U.S. Treasury securities	$	72,862	$	19	$	14	$	72,867
U.S. government agency securities	80,096		306		710		79,692
Mortgage-backed securities	1,458,894		12,789		7,776		1,463,907
State and municipal securities	1,669,606		52,096		7,249		1,714,453
Asset-backed securities	153,963		302		1,293		152,972
Corporate notes and other	56,212		635		743		56,104
	$	3,491,633	$	66,147	17,785		$	3,539,995
Securities held-to-maturity:
State and municipal securities	$	188,996	$	12,221	$	—	$	201,217
	$	188,996	$	12,221	$	—	$	201,217

Amortized Cost and Fair Value of Debt Securities by Contractual Maturity

The amortized cost and fair value of debt securities as of June 30, 2020 by contractual maturity are shown below. Actual maturities may differ from contractual maturities of mortgage- and asset-backed securities since the mortgages and assets underlying the securities may be called or prepaid with or without penalty. Therefore, these securities are not included in the maturity categories in the following summary (in thousands):


	Available-for-sale						Held-to-maturity
June 30, 2020:	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	73,636	$	73,774	$	—	$	—
Due in one year to five years	9,378		9,640		1,000		1,047
Due in five years to ten years	173,763		174,310		2,905		2,979
Due after ten years	1,180,492		1,173,693		1,044,318		1,057,207
Mortgage-backed securities	1,661,910		1,738,446		—		—
Asset-backed securities	142,504		140,415		—		—
	$	3,241,683	$	3,310,278	$	1,048,223	$	1,061,233

Classification of Investments According to Term of Unrealized Losses of Less than Twelve Months or Twelve Months or Longer

At June 30, 2020 and December 31, 2019, the following investments had unrealized losses. The table below classifies these investments according to the term of the unrealized losses of less than twelve months or twelve months or longer (in thousands):


	Investments with an Unrealized Loss of less than 12 months						Investments with an Unrealized Loss of 12 months or longer						Total Investments with an Unrealized Loss
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
At June 30, 2020
U.S. Treasury securities	$	—	$	—	$	—	$	—	$	—	$	—
U.S. government agency securities	—		—		6,507		32		6,507		32
Mortgage-backed securities	59,233		614		43,978		773		103,211		1,387
State and municipal securities	182,186		3,557		496,371		28,448		678,557		32,005
Asset-backed securities	59,994		1,260		54,376		1,350		114,370		2,610
Corporate notes	43,808		1,548		18,650		3,109		62,458		4,657
Total temporarily-impaired securities	$	345,221	$	6,979	$	619,882	$	33,712	$	965,103	$	40,691

At December 31, 2019
U.S. Treasury securities	$	40,505	$	14	$	—	$	—	$	40,505	$	14
U.S. government agency securities	1,222		1		30,892		709		32,114		710
Mortgage-backed securities	458,881		5,102		163,767		2,674		622,648		7,776
State and municipal securities	204,958		1,938		244,884		5,311		449,842		7,249
Asset-backed securities	75,488		796		59,816		497		135,304		1,293
Corporate notes	—		—		16,908		743		16,908		743
Total temporarily-impaired securities	$	781,054	$	7,851	$	516,267	$	9,934	$	1,297,321	$	17,785