Investment securities (Tables)

9 Months Ended

Sep. 30, 2011

Investment 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)
September 30, 2011
Investment securities available for sale:
U.S. Treasury and federal agencies	$	69,668		1,360		—	$	71,028
Obligations of states and political subdivisions		45,805		1,029		42		46,792
Mortgage-backed securities:
Government issued or guaranteed		3,708,714		168,551		227		3,877,038
Privately issued residential		1,441,491		7,136		233,549		1,215,078
Privately issued commercial		19,446		—		2,617		16,829
Collateralized debt obligations		44,064		10,141		2,851		51,354
Other debt securities		216,635		4,164		39,946		180,853
Equity securities		171,357		8,530		2,981		176,906
		5,717,180		200,911		282,213		5,635,878
Investment securities held to maturity:
Obligations of states and political subdivisions		184,472		6,942		19		191,395
Mortgage-backed securities:
Government issued or guaranteed		686,908		28,507		—		715,415
Privately issued		278,433		—		100,052		178,381
Other debt securities		12,024		—		—		12,024
		1,161,837		35,449		100,071		1,097,215
Other securities		376,082		—		—		376,082
Total	$	7,255,099		236,360		382,284	$	7,109,175
December 31, 2010
Investment securities available for sale:
U.S. Treasury and federal agencies	$	61,772		1,680		18	$	63,434
Obligations of states and political subdivisions		59,921		561		57		60,425
Mortgage-backed securities:
Government issued or guaranteed		3,146,054		161,298		1,111		3,306,241
Privately issued residential		1,677,064		10,578		252,081		1,435,561
Privately issued commercial		25,357		—		2,950		22,407
Collateralized debt obligations		95,080		24,754		9,078		110,756
Other debt securities		310,017		26,883		38,000		298,900
Equity securities		119,112		5,098		8,442		115,768
		5,494,377		230,852		311,737		5,413,492
Investment securities held to maturity:
Obligations of states and political subdivisions		191,119		1,944		694		192,369
Mortgage-backed securities:
Government issued or guaranteed		808,108		14,061		—		822,169
Privately issued		312,537		—		114,397		198,140
Other debt securities		12,575		—		—		12,575
		1,324,339		16,005		115,091		1,225,253
Other securities		412,709		—		—		412,709
Total	$	7,231,425		246,857		426,828	$	7,051,454

Changes in credit losses associated with debt securities for which other-than-temporary impairment losses

		000000000			000000000
	Three months ended September 30
	2011			2010
	(in thousands)
Beginning balance	$	298,141			314,263
Additions for credit losses not previously recognized		9,642			9,532
Reductions for increases in cash flows		(90	)		(108	)
Reductions for bond charge-offs		(23,127	)		(11,812	)
Ending balance	$	284,566			311,875

		000000000			000000000
	Nine months ended September 30
	2011			2010
	(in thousands)
Beginning balance	$	327,912			284,513
Additions for credit losses not previously recognized		52,213			46,721
Reductions for increases in cash flows		(5,110	)		(450	)
Reductions for bond charge-offs		(90,449	)		(18,909	)
Ending balance	$	284,566			311,875

Amortized cost and estimated fair value of debt securities by contractual maturity

At September 30, 2011, 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	$	23,908		23,994
Due after one year through five years		77,765		79,896
Due after five years through ten years		15,648		16,947
Due after ten years		258,851		229,190
		376,172		350,027
Mortgage-backed securities available for sale		5,169,651		5,108,945
	$	5,545,823		5,458,972
Debt securities held to maturity:
Due in one year or less	$	23,957		24,144
Due after one year through five years		21,814		22,731
Due after five years through ten years		134,730		140,377
Due after ten years		15,995		16,167
		196,496		203,419
Mortgage-backed securities held to maturity		965,341		893,796
	$	1,161,837		1,097,215

Investment securities in continuous unrealized loss position

A summary of investment securities that as of September 30, 2011 and December 31, 2010 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)
September 30, 2011
Investment securities available for sale:
Obligations of states and political subdivisions	$	656		(5	)		2,389		(37	)
Mortgage-backed securities:
Government issued or guaranteed		46,184		(167	)		3,523		(60	)
Privately issued residential		295,370		(8,164	)		803,491		(225,385	)
Privately issued commercial		—		—			16,829		(2,617	)
Collateralized debt obligations		2,549		(531	)		4,684		(2,320	)
Other debt securities		77,028		(5,252	)		72,961		(34,694	)
Equity securities		9,189		(2,981	)		—		—
		430,976		(17,100	)		903,877		(265,113	)
Investment securities held to maturity:
Obligations of states and political subdivisions		1,542		(11	)		184		(8	)
Privately issued mortgage-backed securities		2,791		(1,116	)		175,590		(98,936	)
		4,333		(1,127	)		175,774		(98,944	)
Total	$	435,309		(18,227	)		1,079,651		(364,057	)

	Less than 12 months					12 months or more
	Fair value		Unrealized losses			Fair value		Unrealized losses
			(in thousands)
December 31, 2010
Investment securities available for sale:
U.S. Treasury and federal agencies	$	27,289		(18	)		—		—
Obligations of states and political subdivisions		3,712		(18	)		2,062		(39	)
Mortgage-backed securities:
Government issued or guaranteed		68,507		(1,079	)		2,965		(32	)
Privately issued residential		61,192		(1,054	)		1,057,315		(251,027	)
Privately issued commercial		—		—			22,407		(2,950	)
Collateralized debt obligations		12,462		(6,959	)		6,004		(2,119	)
Other debt securities		2,134		(10	)		88,969		(37,990	)
Equity securities		5,326		(3,721	)		673		(4,721	)
		180,622		(12,859	)		1,180,395		(298,878	)
Investment securities held to maturity:
Obligations of states and political subdivisions		76,318		(638	)		467		(56	)
Privately issued mortgage-backed securities		—		—			198,140		(114,397	)
		76,318		(638	)		198,607		(114,453	)
Total	$	256,940		(13,497	)		1,379,002		(413,331	)