Investment securities (Tables)

6 Months Ended

Jun. 30, 2023

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, 2023
Investment securities available for sale:
U.S. Treasury and federal agencies	$	7,930,292	$	18	$	237,858	$	7,692,452
Mortgage-backed securities:
Government issued or guaranteed:
Commercial		634,961		—		19,998		614,963
Residential		2,506,882		105		166,959		2,340,028
Other debt securities		176,323		111		16,218		160,216
		11,248,458		234		441,033		10,807,659
Investment securities held to maturity:
U.S. Treasury and federal agencies		1,049,342		—		48,391		1,000,951
Obligations of states and political subdivisions		2,549,551		2,009		103,344		2,448,216
Mortgage-backed securities:
Government issued or guaranteed:
Commercial		2,029,755		—		148,315		1,881,440
Residential		10,241,181		—		909,050		9,332,131
Privately issued		46,636		9,249		6,768		49,117
Other debt securities		1,641		—		—		1,641
		15,918,106		11,258		1,215,868		14,713,496
Total debt securities	$	27,166,564	$	11,492	$	1,656,901	$	25,521,155
Equity and other securities:
Readily marketable equity — at fair value	$	219,405	$	2,137	$	3,374	$	218,168
Other — at cost		972,522		—		—		972,522
Total equity and other securities	$	1,191,927	$	2,137	$	3,374	$	1,190,690
December 31, 2022
Investment securities available for sale:
U.S. Treasury and federal agencies	$	7,913,932	$	200	$	243,172	$	7,670,960
Mortgage-backed securities:
Government issued or guaranteed:
Commercial		594,779		—		20,480		574,299
Residential		2,501,334		65		171,281		2,330,118
Other debt securities		183,107		250		9,773		173,584
		11,193,152		515		444,706		10,748,961
Investment securities held to maturity:
U.S. Treasury and federal agencies		1,054,035		—		45,747		1,008,288
Obligations of states and political subdivisions		2,577,078		4		116,512		2,460,570
Mortgage-backed securities:
Government issued or guaranteed:
Commercial		912,431		—		103,528		808,903
Residential		8,934,918		1,451		891,063		8,045,306
Privately issued		49,742		8,833		7,987		50,588
Other debt securities		1,765		—		—		1,765
		13,529,969		10,288		1,164,837		12,375,420
Total debt securities	$	24,723,121	$	10,803	$	1,609,543	$	23,124,381
Equity and other securities:
Readily marketable equity — at fair value	$	153,283	$	2,120	$	3,945	$	151,458
Other — at cost		780,483		—		—		780,483
Total equity and other securities	$	933,766	$	2,120	$	3,945	$	931,941

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

At June 30, 2023, 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	$	3,470,536	$	3,391,769
Due after one year through five years		4,576,316		4,410,215
Due after five years through ten years		29,763		26,430
Due after ten years		30,000		24,254
		8,106,615		7,852,668
Mortgage-backed securities available for sale		3,141,843		2,954,991
	$	11,248,458	$	10,807,659
Debt securities held to maturity:
Due in one year or less	$	76,348	$	76,153
Due after one year through five years		1,132,418		1,082,030
Due after five years through ten years		1,191,409		1,162,463
Due after ten years		1,200,359		1,130,162
		3,600,534		3,450,808
Mortgage-backed securities held to maturity		12,317,572		11,262,688
	$	15,918,106	$	14,713,496

Investment Securities in Continuous Unrealized Loss Position

A summary of investment securities that as of June 30, 2023 and December 31, 2022 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, 2023
Investment securities available for sale:
U.S. Treasury and federal agencies	$	3,030,061	$	77,628	$	4,657,228	$	160,230
Mortgage-backed securities:
Government issued or guaranteed:
Commercial		84,889		2,187		530,074		17,811
Residential		599,600		25,579		1,718,645		141,380
Other debt securities		5,341		388		149,121		15,830
		3,719,891		105,782		7,055,068		335,251
Investment securities held to maturity:
U.S. Treasury and federal agencies		49,056		966		951,895		47,425
Obligations of states and political subdivisions		585,349		12,092		1,831,988		91,252
Mortgage-backed securities:
Government issued or guaranteed:
Commercial		1,070,875		42,712		810,565		105,603
Residential		2,885,964		62,203		6,446,167		846,847
Privately issued		1,986		82		34,677		6,686
		4,593,230		118,055		10,075,292		1,097,813
Total	$	8,313,121	$	223,837	$	17,130,360	$	1,433,064
December 31, 2022
Investment securities available for sale:
U.S. Treasury and federal agencies	$	6,706,413	$	183,760	$	841,945	$	59,412
Mortgage-backed securities:
Government issued or guaranteed:
Commercial		574,299		20,480		—		—
Residential		2,295,873		169,489		28,305		1,792
Other debt securities		93,458		3,604		73,280		6,169
		9,670,043		377,333		943,530		67,373
Investment securities held to maturity:
U.S. Treasury and federal agencies		1,008,288		45,747		—		—
Obligations of states and political subdivisions		2,449,420		116,512		—		—
Mortgage-backed securities:
Government issued or guaranteed:
Commercial		808,903		103,528		—		—
Residential		6,292,462		619,403		1,319,300		271,660
Privately issued		—		—		35,661		7,987
		10,559,073		885,190		1,354,961		279,647
Total	$	20,229,116	$	1,262,523	$	2,298,491	$	347,020