Investment Securities Held-to-Maturity (Tables)

9 Months Ended

Sep. 30, 2021

Text Block [Abstract]

Summary of Held-to-Maturity Securities

	September 30, 2021								December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
	(in thousands)
U.S. Government Sponsored Enterprises	$	350,583	$	18	$	5,023	$	345,578	$	244,220	$	389	$	866	$	243,743
SBA Backed Securities		38,594		1,295		—		39,889		37,783		2,002		—		39,785
U.S. Government Sponsored Enterprises Mortgage- Backed Securities		2,822,800		31,114		32,122		2,821,792		2,227,085		69,522		1,032		2,295,575
Total	$	3,211,977	$	32,427	$	37,145	$	3,207,259	$	2,509,088	$	71,913	$	1,898	$	2,579,103

Company's Securities Held-to-Maturity

The following table shows the maturity distribution of the Company’s securities held-to-maturity at September 30, 2021.

	Amortized Cost		Fair Value
	(in thousands)
Within one year	$	38,603	$	38,877
After one but within five years		1,790,437		1,804,982
After five but within ten years		1,382,937		1,363,400
More than ten years		—		—
Total	$	3,211,977	$	3,207,259

Unrealized Market Loss of Securities

The following table shows the temporarily impaired securities of the Company’s held-to-maturity portfolio September 30, 2021. This table shows the unrealized market loss of securities that have been in a continuous unrealized loss position for 12 months or less and a continuous loss position for 12 months or longer. There are 149 and 31 securities that are temporarily impaired for less than 12 months and for 12 months or longer, respectively, out of a total of 651 holdings at September 30, 2021.

	September 30, 2021
	Less Than 12 Months				12 Months or Longer				Total
Temporarily Impaired Investments	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(in thousands)
US Government Sponsored Enterprises	$	194,263	$	2,579	$	146,298	$	2,444	$	340,561	$	5,023
SBA Backed Securities		—		—		—		—		—		—
U.S. Government Agency and Sponsored Enterprise Mortgage-Backed Securities		1,585,765		28,423		107,977		3,699		1,693,742		32,122
Total temporarily impaired securities	$	1,780,028	$	31,002	$	254,275	$	6,143	$	2,034,303	$	37,145

The following table shows the temporarily impaired securities of the Company’s held-to-maturity portfolio at December 31, 2020. This table shows the unrealized market loss of securities that have been in a continuous unrealized loss position for less than 12 months and a continuous loss position for 12 months or longer. There are 53 and 0 securities that are temporarily impaired for less than 12 months and for 12 months or longer, respectively, out of a total of 600 holdings at December 31, 2020.

	December 31, 2020
	Less Than 12 Months				12 Months or Longer				Total
Temporarily Impaired Investments	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(in thousands)
U.S. Government Sponsored Enterprises	$	162,870	$	866	$	—	$	—	$	162,870	$	866
SBA Backed Securities		—		—		—		—		—		—
U.S. Government Agency and Sponsored Enterprise Mortgage-Backed Securities		302,401		1,032		—		—		302,401		1,032
Total temporarily impaired securities	$	465,271	$	1,898	$	—	$	—	$	465,271	$	1,898