Investment securities (Tables)

6 Months Ended

Jun. 30, 2022

Investments Debt And Equity Securities [Abstract]

Amortized Cost and Estimated Fair Value of Investment Securities

The amortized cost and estimated fair value of investment securities were as follows:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
	(In thousands)
June 30, 2022
Investment securities available for sale:
U.S. Treasury and federal agencies	$	5,273,377	$	1,568	$	92,374	$	5,182,571
Mortgage-backed securities:
Government issued or guaranteed
Commercial		617,359		—		2,575		614,784
Residential		2,799,742		2,079		75,052		2,726,769
Other debt securities		188,938		433		8,540		180,831
		8,879,416		4,080		178,541		8,704,955
Investment securities held to maturity:
U.S. Treasury and federal agencies		1,337,395		—		18,339		1,319,056
Obligations of states and political subdivisions		2,735,757		53		108,197		2,627,613
Mortgage-backed securities:
Government issued or guaranteed
Commercial		934,161		—		47,527		886,634
Residential		8,308,155		116		503,293		7,804,978
Privately issued		55,397		10,335		10,204		55,528
Other debt securities		2,306		—		—		2,306
		13,373,171		10,504		687,560		12,696,115
Total debt securities	$	22,252,587	$	14,584	$	866,101	$	21,401,070
Equity and other securities:
Readily marketable equity — at fair value	$	98,811	$	5,189	$	2,128	$	101,872
Other — at cost		621,719		—		—		621,719
Total equity and other securities	$	720,530	$	5,189	$	2,128	$	723,591
December 31, 2021
Investment securities available for sale:
U.S. Treasury and federal agencies	$	682,267	$	229	$	3,806	$	678,690
Mortgage-backed securities:
Government issued or guaranteed
Residential		3,042,771		113,102		561		3,155,312
Other debt securities		124,309		1,974		4,481		121,802
		3,849,347		115,305		8,848		3,955,804
Investment securities held to maturity:
U.S. Treasury and federal agencies		3,052		—		9		3,043
Obligations of states and political subdivisions		177		2		—		179
Mortgage-backed securities:
Government issued or guaranteed
Residential		2,667,328		49,221		8,376		2,708,173
Privately issued		61,555		10,520		14,742		57,333
Other debt securities		2,562		—		—		2,562
		2,734,674		59,743		23,127		2,771,290
Total debt securities	$	6,584,021	$	175,048	$	31,975	$	6,727,094
Equity and other securities:
Readily marketable equity — at fair value	$	73,774	$	4,460	$	594	$	77,640
Other — at cost		387,742		—		—		387,742
Total equity and other securities	$	461,516	$	4,460	$	594	$	465,382

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

At June 30, 2022, the amortized cost and estimated fair value of debt securities by contractual maturity were as follows:

	Amortized Cost		Estimated Fair Value
	(In thousands)
Debt securities available for sale:
Due in one year or less	$	8,067	$	8,024
Due after one year through five years		5,344,779		5,251,402
Due after five years through ten years		79,469		77,014
Due after ten years		30,000		26,962
		5,462,315		5,363,402
Mortgage-backed securities available for sale		3,417,101		3,341,553
	$	8,879,416	$	8,704,955
Debt securities held to maturity:
Due in one year or less	$	382,222	$	381,067
Due after one year through five years		1,180,314		1,162,783
Due after five years through ten years		946,218		928,727
Due after ten years		1,566,704		1,476,398
		4,075,458		3,948,975
Mortgage-backed securities held to maturity		9,297,713		8,747,140
	$	13,373,171	$	12,696,115

Investment Securities in Continuous Unrealized Loss Position

A summary of investment securities that as of June 30, 2022 and December 31, 2021 had been in a continuous unrealized loss position for less than twelve months and those that had been in a continuous unrealized loss position for twelve months or longer follows:

	Less Than 12 Months				12 Months or More
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(In thousands)
June 30, 2022
Investment securities available for sale:
U.S. Treasury and federal agencies	$	4,852,107	$	92,364	$	290	$	10
Mortgage-backed securities:
Government issued or guaranteed
Commercial		614,784		2,575		—		—
Residential		2,504,958		74,368		18,856		684
Other debt securities		106,106		2,451		67,567		6,089
		8,077,955		171,758		86,713		6,783
Investment securities held to maturity:
U.S. Treasury and federal agencies		1,319,056		18,339		—		—
Obligations of states and political subdivisions		2,577,044		108,197		—		—
Mortgage-backed securities:
Government issued or guaranteed
Commercial		869,648		47,527		—		—
Residential		7,787,763		503,207		1,083		86
Privately issued		—		—		38,272		10,204
		12,553,511		677,270		39,355		10,290
Total	$	20,631,466	$	849,028	$	126,068	$	17,073
December 31, 2021
Investment securities available for sale:
U.S. Treasury and federal agencies	$	598,566	$	3,806	$	—	$	—
Mortgage-backed securities:
Government issued or guaranteed
Residential		10,111		54		20,824		507
Other debt securities		3,760		74		66,419		4,407
		612,437		3,934		87,243		4,914
Investment securities held to maturity:
U.S. Treasury and federal agencies		3,043		9		—		—
Mortgage-backed securities:
Government issued or guaranteed
Residential		1,372,236		8,356		1,251		20
Privately issued		—		—		43,692		14,742
		1,375,279		8,365		44,943		14,762
Total	$	1,987,716	$	12,299	$	132,186	$	19,676