Investment securities (Tables)

3 Months Ended

Mar. 31, 2020

Fair Value of Available for Sale Securities and Related Gross Unrealized Gains and Losses Recognized in Accumulated Other Comprehensive Income (Loss)

The amortized cost, fair value and allowance for credit losses of available for sale debt securities and the related gross unrealized gains and losses recognized in accumulated other comprehensive income (loss) were as follows:

	March 31, 2020
		Gross	Gross	Allowance
	Amortized	unrealized	unrealized	for credit	Fair
	cost	gains	losses	losses	value
Corporate debt securities	$5,504	$253	$                    —	$                    —	$5,757
Obligations of U.S. government sponsored entities and agencies	147,339	620	—	—	147,959
Mortgage-backed securities	1,711,738	76,108	—	—	1,787,846
U.S. treasuries	100,001	—	4	—	99,997
Municipal securities	90,162	6,721	—	—	96,883
Total available for sale debt securities	$2,054,744	$83,702	$4	$                    —	$2,138,442

	December 31, 2019
		Gross	Gross
	Amortized	Unrealized	Unrealized	Fair
	Cost	Gains	Losses	Value
Corporate debt securities	$5,504	$153	$                    —	$5,657
Obligations of U.S. government sponsored entities and agencies	20,000	—	70	19,930
Mortgage-backed securities	1,742,221	26,403	1,382	1,767,242
Municipal securities	88,301	5,594	—	93,895
Total available for sale debt securities	$1,856,026	$32,150	$1,452	$1,886,724

Schedule of Sales of Available for Sale Securities

Sales of available for sale debt securities for the three-month ended March 31, 2019 were as follows:

For the three months ended:	March 31, 2020	March 31, 2019
Proceeds	$                    —	$66,486
Gross gains	—	646
Gross losses	—	629

Fair Value of Held to Maturity Securities and Related Gross Unrecognized Gains and Losses

The following reflects the amortized cost, fair value and allowance for credit losses and the related gross unrecognized gains and losses of held to maturity securities as of March 31, 2020 and December 31, 2019.

	March 31, 2020
		Gross	Gross		Allowance
	Amortized	unrecognized	unrecognized	Fair	for credit
	cost	gains	losses	value	losses
Mortgage-backed securities	$67,841	$2,317	$                    —	$70,158	$                    —
Municipal securities	128,117	7,183	—	135,300	(10)
Total held to maturity debt securities	$195,958	$9,500	$                    —	$205,458	$(10)

	December 31, 2019
		Gross	Gross
	Amortized	unrecognized	unrecognized	Fair
	cost	gains	losses	value
Mortgage-backed securities	$71,560	$456	$29	$71,987
Municipal securities	131,343	5,522	—	136,865
Total held to maturity debt securities	$202,903	$5,978	$29	$208,852

Available-for-sale Securities [Member]

Fair Value and Amortized Cost of Investment Securities by Contractual Maturity

The fair value of available for sale debt securities at March 31, 2020 by contractual maturity were as follows. Securities not due at a single maturity date, primarily mortgage-backed securities, are shown separately.

	Fair	Amortized
Investment securities available for sale:	Value	Cost
Due one year or less	$102,204	$102,191
Due after one year through five years	131,668	131,295
Due after five years through ten years	45,763	44,017
Due after ten years through thirty years	70,961	65,503
Mortgage-backed securities	1,787,846	1,711,738
Total available for sale debt securities	$2,138,442	$2,054,744

Investments Gross Unrealized Losses and Fair Value

The following tables show the Company’s available for sale debt investments’ gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at March 31, 2020 and December 31, 2019.

	March 31, 2020
	Less than 12 months		12 months or more		Total
	Fair	Unrealized	Fair	Unrealized	Fair	Unrealized
	value	losses	value	losses	value	losses
Mortgage-backed securities	$100	$                 —	$                    —	$                 —	$100	$                 —
U.S. treasuries	99,997	4	—	—	99,997	4
Total temporarily impaired available for sale debt securities	$100,097	$4	$                    —	$                 —	$100,097	$4

	December 31, 2019
	Less than 12 months		12 months or more		Total
	Fair	Unrealized	Fair	Unrealized	Fair	Unrealized
	Value	Losses	Value	Losses	Value	Losses
Obligations of U.S. government sponsored entities and agencies	$19,930	$70	$                 —	$                 —	$19,930	$70
Mortgage-backed securities	125,249	388	117,903	994	243,152	1,382
Total temporarily impaired available for sale debt securities	$145,179	$458	$117,903	$994	$263,082	$1,452

Held-to-maturity Securities [Member]

Fair Value and Amortized Cost of Investment Securities by Contractual Maturity

The fair value and amortized cost of held to maturity securities at March 31, 2020 by contractual maturity were as follows. Mortgage-backed securities are not due at a single maturity date and are shown separately.

	Fair	Amortized
Held to maturity debt securities	value	cost
Due after five years through ten years	$2,193	$2,138
Due after ten years through thirty years	133,107	125,979
Mortgage-backed securities	70,158	67,841
Total held to maturity debt securities	$205,458	$195,958

Investments Gross Unrealized Losses and Fair Value

The following table shows the Company’s held to maturity debt investments’ gross unrecognized losses and fair value, aggregated by investment category and length of time the individual securities have been in a continuous unrecognized loss position, at December 31, 2019.

	December 31, 2019
	Less than 12 months		12 months or more		Total
	Fair	Unrecognized	Fair	Unrecognized	Fair	Unrecognized
	Value	Losses	Value	Losses	Value	Losses
Mortgage-backed securities	$                 —	$                 —	$8,445	$29	$8,445	$29
Total temporarily impaired held to maturity debt securities	$                 —	$                 —	$8,445	$29	$8,445	$29

Schedule of Allowance for Credit Losses on Held to Maturity Debt Investments

The following table shows a roll-forward for the three-month ended March 31, 2020 for the of the allowance for credit losses on held to maturity debt investments:

	Municipal
Held to maturity debt securities	securities
Allowance for credit losses:
Beginning balance, January 1, 2020	$                 —
Impact of adopting ASC 326	10
Provision for credit loss expense	—
Allowance on purchased financial assets with credit deterioration	—
Securities charged off	—
Recoveries	—
Total ending allowance balance	$10

Schedule of Amortized Costs of Held to Maturity Debt Securities Aggregated by Credit Quality Indicator

The following table summarizes the amortized costs of held to maturity debt securities at March 31, 2020, aggregated by credit quality indicator:

	Mortgage-backed	Municipal
	securities	securities
At March 31, 2020
AAA/AA/A	$                    —	$126,737
Not rated (1)	67,841	1,380
Total	$67,841	$128,117

(1) All unrated mortgage-backed securities are FNMA and GNMA. The federal backing of these securities result in negligible credit risk.