Securities (Tables)

3 Months Ended

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

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
March 31, 2019:
Securities available-for-sale:
U.S. Treasury securities	$	48,612	$	5	$	5	$	48,612
U.S. government agency securities	68,219		25		1,275		66,969
Mortgage-backed securities	1,372,248		3,798		16,325		1,359,721
State and municipal securities	1,423,313		30,366		2,948		1,450,731
Asset-backed securities	269,941		1,026		1,957		269,010
Corporate notes and other	56,062		302		1,401		54,963
	$	3,238,395	$	35,522	$	23,911	$	3,250,006
Securities held-to-maturity:
State and municipal securities	$	194,043	$	4,979	$	12	$	199,010
	$	194,043	$	4,979	$	12	$	199,010

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 March 31, 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
March 31, 2019:	Amortized Cost		Fair Value		Amortized  Cost		Fair Value
Due in one year or less	$	63,866	$	63,860	$	325	$	326
Due in one year to five years	22,546		22,533		5,679		5,678
Due in five years to ten years	103,720		103,272		7,962		8,003
Due after ten years	1,406,074		1,431,610		180,077		185,003
Mortgage-backed securities	1,372,248		1,359,721		—		—
Asset-backed securities	269,941		269,010		—		—
	$	3,238,395	$	3,250,006	$	194,043	$	199,010

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

At March 31, 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 March 31, 2019
U.S. Treasury securities	$	29,824	$	3	$	248	$	2	$	30,072	$	5
U.S. government agency securities	6,631		58		51,280		1,217		57,911		1,275
Mortgage-backed securities	82,112		565		987,424		15,760		1,069,536		16,325
State and municipal securities	161,772		2,622		80,686		509		242,458		3,131
Asset-backed securities	152,062		1,534		26,675		423		178,737		1,957
Corporate notes	10,672		719		19,871		682		30,543		1,401
Total temporarily-impaired securities	$	443,073	$	5,501	$	1,166,184	$	18,593	$	1,609,257	$	24,094
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