Investment Securities (Tables)

3 Months Ended

Mar. 31, 2021

Investments, Debt and Equity Securities [Abstract]

Summary of Amortized Cost and Estimated Fair Value of Investment Securities

	March 31, 2021
	Amortized    Cost		Gross    Unrealized    Holding Gain		Gross    Unrealized    Holding Loss			Fair Value		Total Percent
	(Dollars in thousands)
Investment securities available-for-sale:
Mortgage-backed securities	$	2,175,414	$	38,333	$	(22,409)		$	2,191,338		77.92%
CMO/REMIC		592,915		4,072		(6,821)			590,166		20.99%
Municipal bonds		28,703		1,183		-			29,886		1.06%
Other securities		958		-		-			958		0.03%
Total available-for-sale securities	$	2,797,990	$	43,588	$	(29,230)		$	2,812,348		100.00%
Investment securities held-to-maturity:
Government agency/GSE	$	601,142	$	3,860	$	(16,289	)	$	588,713		55.30%
Mortgage-backed securities		135,137		5,348		(255	)		140,230		12.43%
CMO/REMIC		133,556		2,832		-			136,388		12.29%
Municipal bonds		217,149		5,095		(2,094)			220,150		19.98%
Total held-to-maturity securities	$	1,086,984	$	17,135	$	(18,638)		$	1,085,481		100.00%

	December 31, 2020
	Amortized    Cost		Gross    Unrealized    Holding Gain		Gross    Unrealized    Holding Loss		Fair Value		Total Percent
	(Dollars in thousands)
Investment securities available-for-sale:
Mortgage-backed securities	$	1,857,030	$	48,006	$	(101)	$	1,904,935		79.41%
CMO/REMIC		457,548		5,515		(249)		462,814		19.29%
Municipal bonds		28,707		1,578		-		30,285		1.26%
Other securities		889		-		-		889		0.04%
Total available-for-sale securities	$	2,344,174	$	55,099	$	(350)	$	2,398,923		100.00%
Investment securities held-to-maturity:
Government agency/GSE	$	98,663	$	5,877	$	-	$	104,540		17.05%
Mortgage-backed securities		146,382		7,644		(32)		153,994		25.30%
CMO/REMIC		145,309		5,202		-		150,511		25.11%
Municipal bonds		188,272		6,980		(74)		195,178		32.54%
Total held-to-maturity securities	$	578,626	$	25,703	$	(106)	$	604,223		100.00%

Summary of Interest Income Earned on Investment Securities

The following table provides information about the amount of interest income earned on investment securities which is fully taxable and which is exempt from regular federal income tax.

	Three Months Ended
	March 31,
	2021		2020
	(Dollars in thousands)
Investment securities available-for-sale:
Taxable	$	8,968	$	9,825
Tax-advantaged		191		224
Total interest income from available-for-sale securities		9,159		10,049
Investment securities held-to-maturity:
Taxable		2,811		2,698
Tax-advantaged		1,129		1,300
Total interest income from held-to-maturity securities		3,940		3,998
Total interest income from investment securities	$	13,099	$	14,047

Summary of Continuous Unrealized Loss Position of Securities

The following table presents the Company’s available-for-sale investment securities, by investment category, in an unrealized loss position for which an allowance for credit losses has not been recorded as of March 31, 2021 and December 31, 2020.

	March 31, 2021
	Less Than 12 Months					12 Months or Longer				Total
	Fair Value		Gross Unrealized Holding Losses			Fair Value		Gross Unrealized Holding Losses		Fair Value		Gross Unrealized Holding Losses
	(Dollars in thousands)
Investment securities available-for-sale:
Mortgage-backed securities	$	1,327,126	$	(22,409	)	$	-	$	-	$	1,327,126	$	(22,409	)
CMO/REMIC		422,765		(6,821	)		-		-		422,765		(6,821	)
Municipal bonds		-		-			-		-		-		-
Total available-for-sale securities	$	1,749,891	$	(29,230	)	$	-	$	-	$	1,749,891	$	(29,230	)

	December 31, 2020
	Less Than 12 Months					12 Months or Longer				Total
	Fair Value		Gross Unrealized Holding Losses			Fair Value		Gross Unrealized Holding Losses		Fair Value		Gross Unrealized Holding Losses
	(Dollars in thousands)
Investment securities available-for-sale:
Mortgage-backed securities	$	72,219	$	(101	)	$	-	$	-	$	72,219	$	(101	)
CMO/REMIC		96,974		(249	)		-		-		96,974		(249	)
Municipal bonds		-		-			-		-		-		-
Total available-for-sale securities	$	169,193	$	(350	)	$	-	$	-	$	169,193	$	(350	)

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

Mortgage-backed and CMO/REMIC securities are included in maturity categories based upon estimated average lives which incorporate estimated prepayment speeds.

	March 31, 2021
	Available-for-sale				Held-to-maturity
	Amortized   Cost		Fair Value		Amortized   Cost		Fair Value
	(Dollars in thousands)
Due in one year or less	$	4,821	$	4,920	$	4,054	$	4,086
Due after one year through five years		2,368,827		2,383,641		280,057		288,032
Due after five years through ten years		393,699		392,160		133,106		134,081
Due after ten years		30,643		31,627		669,767		659,282
Total investment securities	$	2,797,990	$	2,812,348	$	1,086,984	$	1,085,481