Securities (Tables)

9 Months Ended

Sep. 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 September 30, 2019 and December 31, 2018 are summarized as follows (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
September 30, 2019:
Securities available-for-sale:
U.S. Treasury securities	$	48,635	$	31	$	4	$	48,662
U.S. government agency securities	92,668		412		834		92,246
Mortgage-backed securities	1,318,953		19,229		3,665		1,334,517
State and municipal securities	1,658,734		54,839		13,687		1,699,886
Asset-backed securities	163,334		601		1,202		162,733
Corporate notes and other	55,667		565		841		55,391
	$	3,337,991	$	75,677	$	20,233	$	3,393,435
Securities held-to-maturity:
State and municipal securities	$	189,684	$	13,137	$	—	$	202,821
	$	189,684	$	13,137	$	—	$	202,821



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	1,259,267		1,126		30,739		1,229,654
Asset-backed securities	379,107		820		4,345		375,582
Corporate notes and other	69,399		170		2,523		67,046
	$	3,146,023	$	5,275	67,612		$	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 September 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
September 30, 2019:	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	63,488	$	63,507	$	1,394	$	1,394
Due in one year to five years	16,772		16,986		—		—
Due in five years to ten years	106,774		107,322		5,775		5,877
Due after ten years	1,668,670		1,708,370		182,515		195,550
Mortgage-backed securities	1,318,953		1,334,517		—		—
Asset-backed securities	163,334		162,733		—		—
	$	3,337,991	$	3,393,435	$	189,684	$	202,821

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

At September 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 September 30, 2019
U.S. Treasury securities	$	9,622	$	4	$	—	$	—	$	9,622	$	4
U.S. government agency securities	2,942		5		33,247		829		36,189		834
Mortgage-backed securities	116,784		515		210,395		3,150		327,179		3,665
State and municipal securities	214,033		1,874		383,023		11,813		597,056		13,687
Asset-backed securities	69,921		699		57,709		503		127,630		1,202
Corporate notes	14,959		120		12,053		721		27,012		841
Total temporarily-impaired securities	$	428,261	$	3,217	$	696,427	$	17,016	$	1,124,688	$	20,233

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



	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
State and municipal securities	1,044,757		30,780		198,610		4,078		1,243,367		34,858
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	$	1,586,756	$	38,920	$	1,161,369	$	32,811	$	2,748,125	$	71,731