Securities (Tables)

6 Months Ended

Jun. 30, 2017

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, 2017 and December 31, 2016 are summarized as follows (in thousands):

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
June 30, 2017:
Securities available-for-sale:
U.S. Treasury securities	$	250	$	1	$	—	$	251
U.S. government agency securities	62,659		—		759		61,900
Mortgage-backed securities	1,548,758		5,440		15,148		1,539,050
State and municipal securities	532,508		5,209		4,115		533,602
Asset-backed securities	190,560		134		474		190,220
Corporate notes and other	102,016		182		187		102,011
	$	2,436,751	$	10,966	$	20,683	$	2,427,034
Securities held-to-maturity:
State and municipal securities	$	21,163	$	199	$	40	$	21,322
	$	21,163	$	199	$	40	$	21,322

December 31, 2016:
Securities available-for-sale:
U.S. Treasury securities	$	250	$	—	$	—	$	250
U.S. government agency securities	22,306		—		537		21,769
Mortgage-backed securities	988,008		4,304		15,686		976,626
State and municipal securities	211,581		4,103		2,964		212,720
Asset-backed securities	79,318		111		849		78,580
Corporate notes and other	8,608		39		46		8,601
	$	1,310,071	$	8,557	20,082		$	1,298,546
Securities held-to-maturity:
State and municipal securities	$	25,251	$	87	$	105	$	25,233
	$	25,251	$	87	$	105	$	25,233

Amortized Cost and Fair Value of Debt Securities by Contractual Maturity

The amortized cost and fair value of debt securities as of June 30, 2017 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, 2017:	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	31,917	$	31,811	$	1,021	$	1,023
Due in one year to five years	82,347		83,312		6,603		6,631
Due in five years to ten years	166,329		168,799		10,219		10,323
Due after ten years	416,840		413,842		3,320		3,345
Mortgage-backed securities	1,548,758		1,539,050		—		—
Asset-backed securities	190,560		190,220		—		—
	$	2,436,751	$	2,427,034	$	21,163	$	21,322

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

At June 30, 2017 and December 31, 2016, 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, 2017
U.S. Treasury securities	$	—	$	—	$	—	$	—	$	—	$	—
U.S. government agency securities	49,120		536		12,780		223		61,900		759
Mortgage-backed securities	1,097,974		13,490		85,658		1,658		1,183,632		15,148
State and municipal securities	324,824		3,379		20,830		776		345,654		4,155
Asset-backed securities	113,296		157		19,153		317		132,449		474
Corporate notes	62,023		187		—		—		62,023		187
Total temporarily-impaired securities	$	1,647,237	$	17,749	$	138,421	$	2,974	$	1,785,658	$	20,723
At December 31, 2016
U.S. Treasury securities	$	—	$	—	$	—	$	—	$	—	$	—
U.S. government agency securities	—		—		20,820		537		20,820		537
Mortgage-backed securities	801,213		15,073		43,148		613		844,361		15,686
State and municipal securities	87,277		3,068		312		1		87,589		3,069
Asset-backed securities	14,510		32		34,097		817		48,607		849
Corporate notes	4,810		46		—		—		4,810		46
Total temporarily-impaired securities	$	907,810	$	18,219	$	98,377	$	1,968	$	1,006,187	$	20,187