Securities (Tables)

3 Months Ended

Mar. 31, 2021

Debt Securities, Available-for-sale [Abstract]

Debt Securities Available for Sale

The following table summarizes the amortized cost, gross unrealized gains and losses, the allowance for credit losses and the resulting fair value of debt securities available for sale:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Allowance for Credit Losses		Fair Value
March 31, 2021	(in thousands)
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	4,040,359	$	109,063	$	(45,203)	$	—	$	4,104,219
Other asset-backed securities	359,259		5,216		(5,656)		—		358,819
State and municipal securities	739,570		18,080		(6,365)		—		751,285
U.S. government agency and government-sponsored enterprise securities	278,185		5,349		(1,567)		—		281,967
Total	$	5,417,373	$	137,708	$	(58,791)	$	—	$	5,496,290
December 31, 2020
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	3,640,351	$	178,579	$	(4,543)	$	—	$	3,814,387
Other asset-backed securities	349,904		9,651		(2,076)		—		357,479
State and municipal securities	729,066		25,098		(592)		—		753,572
U.S. government agency and government-sponsored enterprise securities	278,208		6,545		(57)		—		284,696
Total	$	4,997,529	$	219,873	$	(7,268)	$	—	$	5,210,134

Schedule of gross realized gains and losses on sales and calls of securities available for sale

The following table provides the proceeds and both gross realized gains and losses on sales and calls of debt securities available for sale as well as other securities gains and losses for the periods indicated:

	Three Months Ended March 31,
	2021		2020
	(in thousands)
Proceeds from sales of debt securities available for sale	$	—	$	194,105
Gross realized gains from sales of debt securities available for sale	$	—	$	435
Gross realized losses from sales of debt securities available for sale	—		(186)
Other securities gains	—		—
Investment securities gains, net	$	—	$	249

Schedule of Contractual Maturities of Debt Securities Available for Sale

The scheduled contractual maturities of debt securities available for sale at the period presented below are as follows:

	March 31, 2021
	Amortized Cost		Fair Value
	(in thousands)
Due within one year	$	81,385	$	81,986
Due after one year through five years	737,066		765,090
Due after five years through ten years	2,457,820		2,507,546
Due after ten years	2,141,102		2,141,668
Total debt securities available for sale	$	5,417,373	$	5,496,290

Schedule of Securities pledged as collateral

The following table summarizes the carrying value of securities pledged as collateral to secure public funds, borrowings and other purposes as permitted or required by law:

	March 31, 2021
	(in thousands)
To secure public funds	$	477,970
To secure borrowings	109,650
Other securities pledged	217,055
Total securities pledged as collateral	$	804,675

Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses

The following table shows the gross unrealized losses and fair value of the Company’s debt securities available for sale for which an allowance for credit losses has not been recorded, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position as of the dates presented:

	Less than 12 Months				12 Months or More				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
March 31, 2021	(in thousands)
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	1,661,107	$	(44,484)	$	16,463	$	(719)	$	1,677,570	$	(45,203)
Other asset-backed securities	183,636		(5,656)		69		—		183,705		(5,656)
State and municipal securities	311,953		(6,365)		—		—		311,953		(6,365)
U.S. government agency and government-sponsored enterprise securities	149,483		(1,567)		—		—		149,483		(1,567)
Total	$	2,306,179	$	(58,072)	$	16,532	$	(719)	$	2,322,711	$	(58,791)
December 31, 2020
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	575,329	$	(3,728)	$	18,527	$	(815)	$	593,856	$	(4,543)
Other asset-backed securities	143,764		(2,076)		70		—		143,834		(2,076)
State and municipal securities	86,471		(592)		—		—		86,471		(592)
U.S. government agency and government-sponsored enterprise securities	74,943		(57)		—		—		74,943		(57)
Total	$	880,507	$	(6,453)	$	18,597	$	(815)	$	899,104	$	(7,268)