Investment securities (Tables)

3 Months Ended

Mar. 31, 2019

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)
March 31, 2019
Investment securities available for sale:
U.S. Treasury and federal agencies	$	1,144,288	$	4	$	4,864	$	1,139,428
Obligations of states and political subdivisions		1,181		4		4		1,181
Mortgage-backed securities:
Government issued or guaranteed		7,115,459		29,959		91,511		7,053,907
Privately issued		16		—		—		16
Other debt securities		137,742		1,249		7,939		131,052
		8,398,686		31,216		104,318		8,325,584
Investment securities held to maturity:
U.S. Treasury and federal agencies		944,230		735		15		944,950
Obligations of states and political subdivisions		6,810		27		—		6,837
Mortgage-backed securities:
Government issued or guaranteed		2,652,219		11,876		19,472		2,644,623
Privately issued		107,858		12,806		21,060		99,604
Other debt securities		3,582		—		—		3,582
		3,714,699		25,444		40,547		3,699,596
Total debt securities	$	12,113,385	$	56,660	$	144,865	$	12,025,180
Equity and other securities:
Readily marketable equity — at fair value	$	48,261	$	28,913	$	588	$	76,586
Other — at cost		419,971		—		—		419,971
Total equity and other securities	$	468,232	$	28,913	$	588	$	496,557

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
	(In thousands)
December 31, 2018
Investment securities available for sale:
U.S. Treasury and federal agencies	$	1,346,782	$	—	$	9,851	$	1,336,931
Obligations of states and political subdivisions		1,660		4		5		1,659
Mortgage-backed securities:
Government issued or guaranteed		7,383,340		15,754		182,103		7,216,991
Privately issued		24		—		2		22
Other debt securities		137,617		770		11,481		126,906
		8,869,423		16,528		203,442		8,682,509
Investment securities held to maturity:
U.S. Treasury and federal agencies		446,542		—		239		446,303
Obligations of states and political subdivisions		7,494		22		12		7,504
Mortgage-backed securities:
Government issued or guaranteed		2,745,776		4,165		55,111		2,694,830
Privately issued		113,160		12,345		22,327		103,178
Other debt securities		3,668		—		—		3,668
		3,316,640		16,532		77,689		3,255,483
Total debt securities	$	12,186,063	$	33,060	$	281,131	$	11,937,992
Equity and other securities:
Readily marketable equity — at fair value	$	77,440	$	17,295	$	818	$	93,917
Other — at cost		599,747		—		—		599,747
Total equity and other securities	$	677,187	$	17,295	$	818	$	693,664

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

At March 31, 2019, 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	$	1,141,640		1,136,864
Due after one year through five years		9,470		9,355
Due after five years through ten years		102,101		99,642
Due after ten years		30,000		25,800
		1,283,211		1,271,661
Mortgage-backed securities available for sale		7,115,475		7,053,923
	$	8,398,686		8,325,584
Debt securities held to maturity:
Due in one year or less	$	947,176		947,905
Due after one year through five years		3,864		3,882
Due after ten years		3,582		3,582
		954,622		955,369
Mortgage-backed securities held to maturity		2,760,077		2,744,227
	$	3,714,699		3,699,596

Investment Securities in Continuous Unrealized Loss Position

A summary of investment securities that as of March 31, 2019 and December 31, 2018 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)
March 31, 2019
Investment securities available for sale:
U.S. Treasury and federal agencies	$	274		(1	)		1,137,550		(4,863	)
Obligations of states and political subdivisions		—		—			507		(4	)
Mortgage-backed securities:
Government issued or guaranteed		18,447		(111	)		5,076,762		(91,400	)
Other debt securities		36,500		(294	)		67,662		(7,645	)
		55,221		(406	)		6,282,481		(103,912	)
Investment securities held to maturity:
U.S. Treasury and federal agencies		249,082		(15	)		—		—
Mortgage-backed securities:
Government issued or guaranteed		—		—			1,620,580		(19,472	)
Privately issued		—		—			51,091		(21,060	)
		249,082		(15	)		1,671,671		(40,532	)
Total	$	304,303		(421	)		7,954,152		(144,444	)
December 31, 2018
Investment securities available for sale:
U.S. Treasury and federal agencies	$	273		(2	)		1,335,559		(9,849	)
Obligations of states and political subdivisions		629		(5	)		—		—
Mortgage-backed securities:
Government issued or guaranteed		405,558		(2,892	)		5,646,773		(179,211	)
Privately issued		22		(2	)		—		—
Other debt securities		53,478		(2,187	)		66,014		(9,294	)
		459,960		(5,088	)		7,048,346		(198,354	)
Investment securities held to maturity:
U.S. Treasury and federal agencies		446,303		(239	)		—		—
Obligations of states and political subdivisions		—		—			3,126		(12	)
Mortgage-backed securities:
Government issued or guaranteed		179,354		(989	)		2,082,723		(54,122	)
Privately issued		—		—			51,943		(22,327	)
		625,657		(1,228	)		2,137,792		(76,461	)
Total	$	1,085,617		(6,316	)		9,186,138		(274,815	)