Securities (Tables)

6 Months Ended

Jun. 30, 2019

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, 2019 and December 31, 2018 are summarized as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
June 30, 2019:
Securities available-for-sale:
U.S. Treasury securities	$	48,883	$	34	$	—	$	48,917
U.S. government agency securities	55,907		111		995		55,023
Mortgage-backed securities	1,289,189		9,155		6,431		1,291,913
State and municipal securities	1,572,847		64,161		506		1,636,502
Asset-backed securities	169,457		942		976		169,423
Corporate notes and other	56,179		462		1,513		55,128
	$	3,192,462	$	74,865	$	10,421	$	3,256,906
Securities held-to-maturity:
State and municipal securities	$	190,928	$	9,639	$	1	$	200,566
	$	190,928	$	9,639	$	1	$	200,566



December 31, 2018:
Securities available-for-sale:
U.S. Treasury securities	$	30,325	$	—	$	25	$	30,300
U.S. government agency securities	71,456		49		1,346		70,159
Mortgage-backed securities	1,336,469		3,110		28,634		1,310,945
State and municipal securities	1,244,471		3,785		18,602		1,229,654
Asset-backed securities	379,107		820		4,345		375,582
Corporate notes and other	69,399		170		2,523		67,046
	$	3,131,227	$	7,934	55,475		$	3,083,686
Securities held-to-maturity:
State and municipal securities	$	194,282	$	152	$	1,303	$	193,131
	$	194,282	$	152	$	1,303	$	193,131

Amortized Cost and Fair Value of Debt Securities by Contractual Maturity

The amortized cost and fair value of debt securities as of June 30, 2019 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, 2019:	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	64,432	$	64,479	$	1,401	$	1,401
Due in one year to five years	18,158		18,203		1,020		1,022
Due in five years to ten years	85,576		85,416		5,779		5,866
Due after ten years	1,565,650		1,627,472		182,728		192,277
Mortgage-backed securities	1,289,189		1,291,913		—		—
Asset-backed securities	169,457		169,423		—		—
	$	3,192,462	$	3,256,906	$	190,928	$	200,566

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

At June 30, 2019 and December 31, 2018, 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, 2019
U.S. Treasury securities	$	—	$	—	$	250	$	—	$	250	$	—
U.S. government agency securities	2,064		9		35,391		986		37,455		995
Mortgage-backed securities	84,937		535		471,224		5,896		556,161		6,431
State and municipal securities	76,291		489		11,663		53		87,954		542
Asset-backed securities	104,510		775		22,373		201		126,883		976
Corporate notes	17,337		508		10,502		1,005		27,839		1,513
Total temporarily-impaired securities	$	285,139	$	2,316	$	551,403	$	8,141	$	836,542	$	10,457

At December 31, 2018
U.S. Treasury securities	$	30,054	$	22	$	246	$	3	$	30,300	$	25
U.S. government agency securities	13,697		328		42,539		1,018		56,236		1,346
Mortgage-backed securities	203,299		2,134		882,231		26,500		1,085,530		28,634
State and municipal securities	805,821		18,643		198,610		4,078		1,004,431		22,721
Asset-backed securities	268,677		4,118		11,828		227		280,505		4,345
Corporate notes	26,272		1,538		25,915		985		52,187		2,523
Total temporarily-impaired securities	$	1,347,820	$	26,783	$	1,161,369	$	32,811	$	2,509,189	$	59,594