Investment securities (Tables)

3 Months Ended

Mar. 31, 2015

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, 2015
Investment securities available for sale:
U.S. Treasury and federal agencies	$	161,672		1,563		1	$	163,234
Obligations of states and political subdivisions		7,704		199		53		7,850
Mortgage-backed securities:
Government issued or guaranteed		10,008,191		265,739		8,709		10,265,221
Privately issued		96		2		3		95
Collateralized debt obligations		29,704		19,360		1,786		47,278
Other debt securities		138,366		1,909		19,002		121,273
Equity securities		79,987		18,999		437		98,549
		10,425,720		307,771		29,991		10,703,500
Investment securities held to maturity:
Obligations of states and political subdivisions		148,698		2,178		350		150,526
Mortgage-backed securities:
Government issued or guaranteed		3,007,420		88,417		4,024		3,091,813
Privately issued		197,509		1,421		36,620		162,310
Other debt securities		7,185		—		—		7,185
		3,360,812		92,016		40,994		3,411,834
Other securities		328,958		—		—		328,958
Total	$	14,115,490		399,787		70,985	$	14,444,292
December 31, 2014
Investment securities available for sale:
U.S. Treasury and federal agencies	$	161,408		544		5	$	161,947
Obligations of states and political subdivisions		8,027		224		53		8,198
Mortgage-backed securities:
Government issued or guaranteed		8,507,571		223,889		337		8,731,123
Privately issued		104		2		3		103
Collateralized debt obligations		30,073		21,276		1,033		50,316
Other debt securities		138,240		1,896		18,648		121,488
Equity securities		73,901		11,020		1,164		83,757
		8,919,324		258,851		21,243		9,156,932
Investment securities held to maturity:
Obligations of states and political subdivisions		148,961		2,551		189		151,323
Mortgage-backed securities:
Government issued or guaranteed		3,149,320		78,485		7,000		3,220,805
Privately issued		201,733		1,143		44,576		158,300
Other debt securities		7,854		—		—		7,854
		3,507,868		82,179		51,765		3,538,282
Other securities		328,742		—		—		328,742
Total	$	12,755,934		341,030		73,008	$	13,023,956

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

At March 31, 2015, 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	$	9,059		9,117
Due after one year through five years		163,114		165,027
Due after five years through ten years		3,272		3,314
Due after ten years		162,001		162,177
		337,446		339,635
Mortgage-backed securities available for sale		10,008,287		10,265,316
	$	10,345,733		10,604,951
Debt securities held to maturity:
Due in one year or less	$	27,663		27,865
Due after one year through five years		87,320		88,357
Due after five years through ten years		33,715		34,304
Due after ten years		7,185		7,185
		155,883		157,711
Mortgage-backed securities held to maturity		3,204,929		3,254,123
	$	3,360,812		3,411,834

Investment Securities in Continuous Unrealized Loss Position

A summary of investment securities that as of March 31, 2015 and December 31, 2014 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, 2015
Investment securities available for sale:
U.S. Treasury and federal agencies	$	4,681		(1	)		—		—
Obligations of states and political subdivisions		986		(4	)		1,524		(49	)
Mortgage-backed securities:
Government issued or guaranteed		1,603,068		(8,597	)		4,138		(112	)
Privately issued		—		—			59		(3	)
Collateralized debt obligations		6,091		(1,255	)		5,220		(531	)
Other debt securities		12,689		(443	)		92,304		(18,559	)
Equity securities		374		(437	)		—		—
		1,627,889		(10,737	)		103,245		(19,254	)
Investment securities held to maturity:
Obligations of states and political subdivisions		35,272		(317	)		1,802		(33	)
Mortgage-backed securities:
Government issued or guaranteed		16,660		(85	)		266,979		(3,939	)
Privately issued		—		—			131,779		(36,620	)
		51,932		(402	)		400,560		(40,592	)
Total	$	1,679,821		(11,139	)		503,805		(59,846	)
December 31, 2014
Investment securities available for sale:
U.S. Treasury and federal agencies	$	6,505		(5	)		—		—
Obligations of states and political subdivisions		1,785		(52	)		121		(1	)
Mortgage-backed securities:
Government issued or guaranteed		39,001		(186	)		5,555		(151	)
Privately issued		—		—			65		(3	)
Collateralized debt obligations		2,108		(696	)		5,512		(337	)
Other debt securities		14,017		(556	)		92,661		(18,092	)
Equity securities		2,138		(1,164	)		—		—
		65,554		(2,659	)		103,914		(18,584	)
Investment securities held to maturity:
Obligations of states and political subdivisions		29,886		(184	)		268		(5	)
Mortgage-backed securities:
Government issued or guaranteed		137,413		(361	)		446,780		(6,639	)
Privately issued		—		—			127,512		(44,576	)
		167,299		(545	)		574,560		(51,220	)
Total	$	232,853		(3,204	)		678,474		(69,804	)