Securities (Tables)

3 Months Ended

Mar. 31, 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 March 31, 2020 and December 31, 2019 are summarized as follows (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
March 31, 2020:
Securities available-for-sale:
U.S. Treasury securities	$	72,809	$	391	$	—	$	73,200
U.S. government agency securities	92,162		1,237		1,072		92,327
Mortgage-backed securities	1,558,424		63,092		2,936		1,618,580
State and municipal securities	1,060,142		17,916		41,439		1,036,619
Asset-backed securities	160,004		47		13,591		146,460
Corporate notes and other	66,207		310		3,139		63,378
	$	3,009,748	$	82,993	$	62,177	$	3,030,564
Securities held-to-maturity:
State and municipal securities	$	1,059,405	$	14,019	$	22,333	$	1,051,091
	$	1,059,405	$	14,019	$	22,333	$	1,051,091
Allowance for credit losses - securities held-to-maturity	(148)
Securities held-to-maturity, net of allowance for credit losses	$	1,059,257


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 March 31, 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
March 31, 2020:	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	73,838	$	74,226	$	1,055	$	1,055
Due in one year to five years	10,770		10,946		—		—
Due in five years to ten years	149,431		148,673		5,768		5,863
Due after ten years	1,057,281		1,031,679		1,052,582		1,044,173
Mortgage-backed securities	1,558,424		1,618,580		—		—
Asset-backed securities	160,004		146,460		—		—
	$	3,009,748	$	3,030,564	$	1,059,405	$	1,051,091

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

At March 31, 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 March 31, 2020
U.S. Treasury securities	$	—	$	—	$	—	$	—	$	—	$	—
U.S. government agency securities	—		—		26,858		1,072		26,858		1,072
Mortgage-backed securities	127,612		1,599		61,820		1,337		189,432		2,936
State and municipal securities	137,622		6,616		487,471		35,555		625,093		42,171
Asset-backed securities	80,904		7,905		48,125		5,686		129,029		13,591
Corporate notes	19,269		1,439		8,300		1,700		27,569		3,139
Total temporarily-impaired securities	$	365,407	$	17,559	$	632,574	$	45,350	$	997,981	$	62,909

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