Investment securities (Tables)

9 Months Ended

Sep. 30, 2017

Investments Debt And Equity Securities [Abstract]

Summary of Amortized Cost of Securities and Fair Values

The amortized cost of securities and their fair values at September 30, 2017 and December 31, 2016 are shown below:

	September 30, 2017
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Securities Available-for-Sale
Debt securities
U.S. government agency securities	$	999	$	—	$	(7	)	$	992
Mortgage-backed securities - residential		423,174		586		(4,966	)		418,794
Municipals, tax exempt		104,957		2,657		(664	)		106,950
Treasury securities		8,836		—		(17	)		8,819
Total debt securities		537,966		3,243		(5,654	)		535,555
Equity securities		7,853		1		(127	)		7,727
Total securities available-for-sale	$	545,819	$	3,244	$	(5,781	)	$	543,282

	December 31, 2016
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Securities Available-for-Sale
Debt securities
U.S. government agency securities	$	998	$	—	$	(13	)	$	985
Mortgage-backed securities - residential		450,874		939		(7,905	)		443,908
Municipals, tax exempt		116,034		3,003		(2,114	)		116,923
Treasury securities		11,809		—		(52	)		11,757
Total debt securities		579,715		3,942		(10,084	)		573,573
Equity securities		8,744		1		(135	)		8,610
Total securities available-for-sale	$	588,459	$	3,943	$	(10,219	)	$	582,183

Schedule of Amortized Cost and Fair Value of Debt Securities by Contractual Maturity

Therefore, mortgage-backed securities are not included in the maturity categories in the following maturity summary.

	September 30, 2017				December 31, 2016
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	2,036	$	2,037	$	9,290	$	9,352
Due in one to five years		27,722		28,535		25,520		26,340
Due in five to ten years		17,362		17,851		31,122		32,248
Due in over ten years		67,672		68,338		62,909		61,725
		114,792		116,761		128,841		129,665
Mortgage-backed securities - residential		423,174		418,794		450,874		443,908
Total debt securities	$	537,966	$	535,555	$	579,715	$	573,573

Summary of Sales and Impairment of Available-for-Sale Securities

Sales and impairment of available-for-sale securities were as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Proceeds from sales	$	82,585	$	1,668	$	94,743	$	270,663
Gross realized gains		1,199		416		1,276		4,755
Gross realized losses		—		—		48		348
Other-than-temporary-impairment	945			—	945			—

Schedule of Gross Unrealized Losses

The following tables show gross unrealized losses at September 30, 2017 and December 31, 2016, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	September 30, 2017
	Less than 12 months				12 months or more				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized loss
U.S. government agency securities	$	—	$	—	$	993	$	7	$	993	$	7
Mortgage-backed securities - residential		354,240		3,800		40,115		1,166		394,355		4,966
Municipals, tax exempt		35,240		493		4,155		171		39,395		664
Treasury securities		8,819		17		—		—		8,819	$	17
Total debt securities		398,299		4,310		45,263		1,344		443,562		5,654
Equity securities		—		—		3,054		127		3,054		127
	$	398,299	$	4,310	$	48,317	$	1,471	$	446,616	$	5,781

	December 31, 2016
	Less than 12 months				12 months or more				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized loss
U.S. government agency securities	$	985	$	13	$	—	$	—	$	985	$	13
Mortgage-backed securities - residential		390,595		7,230		19,073		675		409,668		7,905
Municipals, tax exempt		43,132		2,114		—		—		43,132		2,114
Treasury securities		10,256		52		—		—		10,256		52
Total debt securities		444,968		9,409		19,073		675		464,041		10,084
Equity securities		—		—		3,126		135		3,126		135
	$	444,968	$	9,409	$	22,199	$	810	$	467,167	$	10,219

Schedule of Other Than Temporary Impairment, Credit Losses Recognized In Earnings

Changes in the amount of credit related losses recognized in earnings for which OTTI has been recognized are as follows:

Balance as of January 1, 2017	$	—
Additions related to credit losses for which OTTI was not previously recognized		(945	)
Reductions for securities sold during the period		—
Reductions for securities where there is an intent to sale or requirement to sale		—
Increases in credit loss for which OTTI was previously recognized		—
Reductions for increases in cash flows expected to be collected		—
Balance as of September 30, 2017	$	(945	)