Investment Securities (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value, Option, Quantitative Disclosures [Line Items]

Summary of Securities Available for Sale

The following tables present the amortized cost, gross unrealized gains, gross unrealized losses and the fair value for available for sale debt securities at March 31, 2018 and December 31, 2017 (in thousands):

	March 31, 2018
	Amortized cost		Gross unrealized gains	Gross unrealized losses		Fair value
Agency obligations	$	7,007	—	(8	)	6,999
Mortgage-backed securities	1,021,819		2,372	(20,588	)	1,003,603
State and municipal obligations	3,249		81	—		3,330
Corporate obligations	25,044		377	(49	)	25,372
	$	1,057,119	2,830	(20,645	)	1,039,304

	December 31, 2017
	Amortized cost		Gross unrealized gains	Gross unrealized losses		Fair value
Agency obligations	$	19,014	—	(9	)	19,005
Mortgage-backed securities	993,548		4,914	(10,095	)	988,367
State and municipal obligations	3,259		129	—		3,388
Corporate obligations	26,047		359	(12	)	26,394
	$	1,041,868	5,402	(10,116	)	1,037,154

Summary of Available for Sale Securities with Temporary Impairment

The following tables present the fair value and gross unrealized losses for available for sale debt securities with temporary impairment at March 31, 2018 and December 31, 2017 (in thousands):

	March 31, 2018 Unrealized Losses
	Less than 12 months				12 months or longer			Total
	Fair  value		Gross unrealized losses		Fair value	Gross unrealized losses		Fair value	Gross unrealized losses
Agency obligations	$	5,000	(7	)	1,999	(1	)	6,999	(8	)
Mortgage-backed securities	646,962		(11,513	)	227,119	(9,075	)	874,081	(20,588	)
Corporate obligations	7,959		(49	)	—	—		7,959	(49	)
	$	659,921	(11,569	)	229,118	(9,076	)	889,039	(20,645	)

	December 31, 2017 Unrealized Losses
	Less than 12 months				12 months or longer			Total
	Fair value		Gross unrealized losses		Fair value	Gross unrealized losses		Fair value	Gross unrealized losses
Agency obligations	$	12,006	(8	)	6,999	(1	)	19,005	(9	)
Mortgage-backed securities	420,746		(3,936	)	235,056	(6,159	)	655,802	(10,095	)
Corporate obligations	—		—		989	(12	)	989	(12	)
	$	432,752	(3,944	)	243,044	(6,172	)	675,796	(10,116	)

Summary of Investment Securities Held to Maturity

The following tables present the fair value and gross unrealized losses on securities in the held to maturity debt securities portfolio with temporary impairment at March 31, 2018 and December 31, 2017 (in thousands):

	March 31, 2018 Unrealized Losses
	Less than 12 months				12 months or longer			Total
	Fair value		Gross unrealized losses		Fair value	Gross unrealized losses		Fair value	Gross unrealized losses
Agency obligations	$	4,489	(127	)	—	—		4,489	(127	)
State and municipal obligations	167,074		(2,650	)	47,558	(2,733	)	214,632	(5,383	)
Corporate obligations	9,523		(189	)	—	—		9,523	(189	)
	$	181,086	(2,966	)	47,558	(2,733	)	228,644	(5,699	)

	December 31, 2017 Unrealized Losses
	Less than 12 months				12 months or longer			Total
	Fair value		Gross unrealized losses		Fair value	Gross unrealized losses		Fair value	Gross unrealized losses
Agency obligations	$	3,821	(87	)	—	—		3,821	(87	)
State and municipal obligations	37,317		(295	)	49,488	(1,443	)	86,805	(1,738	)
Corporate obligations	9,662		(83	)	—			9,662	(83	)
	$	50,800	(465	)	49,488	(1,443	)	100,288	(1,908	)

The following tables present the amortized cost, gross unrealized gains, gross unrealized losses and the estimated fair value for held to maturity debt securities at March 31, 2018 and December 31, 2017 (in thousands):

	March 31, 2018
	Amortized cost		Gross unrealized gains	Gross unrealized losses			Fair value
Agency obligations	$	4,616	—	(127		)	4,489
Mortgage-backed securities	311		11	—			322
State and municipal obligations	452,031		4,529	(5,383		)	451,177
Corporate obligations	9,987		1	(189		)	9,799
	$	466,945	4,541	$	(5,699	)	465,787

	December 31, 2017
	Amortized cost		Gross unrealized gains	Gross unrealized losses		Fair value
Agency obligations	$	4,308	—	(87	)	4,221
Mortgage-backed securities	382		14	—		396
State and municipal obligations	462,942		9,280	(1,738	)	470,484
Corporate obligations	10,020		1	(83	)	9,938
	$	477,652	9,295	(1,908	)	485,039

Available-for-sale Securities [Member]

Fair Value, Option, Quantitative Disclosures [Line Items]

Summary of Investment Securities Classified by Contractual Maturity

The amortized cost and fair value of available for sale debt securities at March 31, 2018, by contractual maturity, are shown below (in thousands). Expected maturities may differ from contractual maturities due to prepayment or early call privileges of the issuer.

	March 31, 2018
	Amortized cost		Fair value
Due in one year or less	$	7,397	7,392
Due after one year through five years	3,008		2,979
Due after five years through ten years	24,895		25,330
Due after ten years	—		—
	$	35,300	35,701

Held-to-maturity Securities [Member]

Fair Value, Option, Quantitative Disclosures [Line Items]

Summary of Investment Securities Classified by Contractual Maturity

The amortized cost and fair value of held to maturity debt securities at March 31, 2018, by contractual maturity, are shown below (in thousands). Expected maturities may differ from contractual maturities due to prepayment or early call privileges of the issuer.

	March 31, 2018
	Amortized cost		Fair value
Due in one year or less	$	7,452	7,488
Due after one year through five years	71,292		71,458
Due after five years through ten years	255,234		254,865
Due after ten years	132,656		131,654
	$	466,634	465,465