Investment securities (Tables)

6 Months Ended

Jun. 30, 2016

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, 2016
Investment securities available for sale:
U.S. Treasury and federal agencies	$	397,825		2,537		14	$	400,348
Obligations of states and political subdivisions		5,158		131		48		5,241
Mortgage-backed securities:
Government issued or guaranteed		10,944,676		323,828		1,226		11,267,278
Privately issued		58		—		1		57
Collateralized debt obligations		28,255		17,466		2,416		43,305
Other debt securities		135,170		1,271		21,670		114,771
Equity securities		67,687		20,448		161		87,974
		11,578,829		365,681		25,536		11,918,974
Investment securities held to maturity:
Obligations of states and political subdivisions		84,614		712		240		85,086
Mortgage-backed securities:
Government issued or guaranteed		2,315,012		88,526		350		2,403,188
Privately issued		168,784		927		40,737		128,974
Other debt securities		6,011		—		—		6,011
		2,574,421		90,165		41,327		2,623,259
Other securities		469,689		—		—		469,689
Total	$	14,622,939		455,846		66,863	$	15,011,922
December 31, 2015
Investment securities available for sale:
U.S. Treasury and federal agencies	$	299,890		294		187	$	299,997
Obligations of states and political subdivisions		5,924		146		42		6,028
Mortgage-backed securities:
Government issued or guaranteed		11,592,959		142,370		48,701		11,686,628
Privately issued		74		2		2		74
Collateralized debt obligations		28,438		20,143		1,188		47,393
Other debt securities		137,556		1,514		20,190		118,880
Equity securities		73,795		10,230		354		83,671
		12,138,636		174,699		70,664		12,242,671
Investment securities held to maturity:
Obligations of states and political subdivisions		118,431		1,003		421		119,013
Mortgage-backed securities:
Government issued or guaranteed		2,553,612		50,936		7,817		2,596,731
Privately issued		181,091		2,104		41,367		141,828
Other debt securities		6,575		—		—		6,575
		2,859,709		54,043		49,605		2,864,147
Other securities		554,059		—		—		554,059
Total	$	15,552,404		228,742		120,269	$	15,660,877

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

At June 30, 2016, 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	$	6,147		6,176
Due after one year through five years		399,312		402,100
Due after five years through ten years		3,425		3,822
Due after ten years		157,524		151,567
		566,408		563,665
Mortgage-backed securities available for sale		10,944,734		11,267,335
	$	11,511,142		11,831,000
Debt securities held to maturity:
Due in one year or less	$	28,259		28,430
Due after one year through five years		51,414		51,611
Due after five years through ten years		4,941		5,045
Due after ten years		6,011		6,011
		90,625		91,097
Mortgage-backed securities held to maturity		2,483,796		2,532,162
	$	2,574,421		2,623,259

Investment Securities in Continuous Unrealized Loss Position

A summary of investment securities that as of June 30, 2016 and December 31, 2015 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, 2016
Investment securities available for sale:
U.S. Treasury and federal agencies	$	7,831		(14	)		—		—
Obligations of states and political subdivisions		—		—			1,703		(48	)
Mortgage-backed securities:
Government issued or guaranteed		245,977		(1,123	)		7,590		(103	)
Privately issued		—		—			40		(1	)
Collateralized debt obligations		2,883		(1,078	)		4,285		(1,338	)
Other debt securities		11,275		(409	)		91,997		(21,261	)
Equity securities		—		—			140		(161	)
		267,966		(2,624	)		105,755		(22,912	)
Investment securities held to maturity:
Obligations of states and political subdivisions		15,813		(89	)		12,057		(151	)
Mortgage-backed securities:
Government issued or guaranteed		—		—			125,116		(350	)
Privately issued		17,436		(3,075	)		94,454		(37,662	)
		33,249		(3,164	)		231,627		(38,163	)
Total	$	301,215		(5,788	)		337,382		(61,075	)
December 31, 2015
Investment securities available for sale:
U.S. Treasury and federal agencies	$	147,508		(187	)		—		—
Obligations of states and political subdivisions		865		(2	)		1,335		(40	)
Mortgage-backed securities:
Government issued or guaranteed		4,061,899		(48,534	)		7,216		(167	)
Privately issued		—		—			43		(2	)
Collateralized debt obligations		5,711		(335	)		2,063		(853	)
Other debt securities		12,935		(462	)		93,344		(19,728	)
Equity securities		18,073		(207	)		153		(147	)
		4,246,991		(49,727	)		104,154		(20,937	)
Investment securities held to maturity:
Obligations of states and political subdivisions		42,913		(335	)		5,853		(86	)
Mortgage-backed securities:
Government issued or guaranteed		459,983		(1,801	)		228,867		(6,016	)
Privately issued		—		—			112,155		(41,367	)
		502,896		(2,136	)		346,875		(47,469	)
Total	$	4,749,887		(51,863	)		451,029		(68,406	)