Investment securities (Tables)

6 Months Ended

Jun. 30, 2011

Investment securities (Tables) [Abstract]

Amortized cost and estimated fair value of investment securities

			Gross		Gross
	Amortized		unrealized		unrealized		Estimated
	cost		gains		losses		fair value
			(in thousands)
June 30, 2011
Investment securities available for sale:
U.S. Treasury and federal agencies	$	111,836		1,119		2	$	112,953
Obligations of states and political subdivisions		66,709		821		39		67,491
Mortgage-backed securities:
Government issued or guaranteed		2,965,034		60,965		2,981		3,023,018
Privately issued residential		1,507,748		9,720		211,266		1,306,202
Privately issued commercial		21,094		—		3,861		17,233
Collateralized debt obligations		44,268		18,800		1,467		61,601
Other debt securities		217,812		5,738		28,014		195,536
Equity securities		92,380		14,526		451		106,455
		5,026,881		111,689		248,081		4,890,489
Investment securities held to maturity:
Obligations of states and political subdivisions		184,595		4,239		149		188,685
Mortgage-backed securities:
Government issued or guaranteed		730,785		21,978		—		752,763
Privately issued		292,034		357		102,615		189,776
Other debt securities		12,272		—		—		12,272
		1,219,686		26,574		102,764		1,143,496
Other securities		382,090		—		—		382,090
Total	$	6,628,657		138,263		350,845	$	6,416,075
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

	Three months ended June 30
	2011			2010
	(in thousands)
Beginning balance	$	322,719			308,017
Additions for credit losses not previously recognized		26,530			10,387
Reductions for increases in cash flows		(4,881	)		(173	)
Reductions for realized losses		(46,227	)		(3,968	)
Ending balance	$	298,141			314,263

	Six months ended June 30
	2011			2010
	(in thousands)
Beginning balance	$	327,912			284,513
Additions for credit losses not previously recognized		42,571			37,189
Reductions for increases in cash flows		(5,020	)		(342	)
Reductions for realized losses		(67,322	)		(7,097	)
Ending balance	$	298,141			314,263

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

			Estimated
	Amortized cost		fair value
	(in thousands)
Debt securities available for sale:
Due in one year or less	$	26,403		26,521
Due after one year through five years		119,212		121,204
Due after five years through ten years		16,687		18,081
Due after ten years		278,323		271,775
		440,625		437,581
Mortgage-backed securities available for sale		4,493,876		4,346,453
	$	4,934,501		4,784,034
Debt securities held to maturity:
Due in one year or less	$	23,428		23,607
Due after one year through five years		20,126		20,775
Due after five years through ten years		134,952		138,114
Due after ten years		18,361		18,461
		196,867		200,957
Mortgage-backed securities held to maturity		1,022,819		942,539
	$	1,219,686		1,143,496

Investment securities in continuous unrealized loss position

	Less than 12 months					12 months or more
			Unrealized					Unrealized
	Fair value		losses			Fair value		losses
			(in thousands)
June 30, 2011
Investment securities available for sale:
U.S. Treasury and federal agencies	$	1,903		(2	)		—		—
Obligations of states and political subdivisions		1,444		(6	)		2,323		(33	)
Mortgage-backed securities:
Government issued or guaranteed		632,513		(2,937	)		3,010		(44	)
Privately issued residential		146,893		(1,859	)		859,930		(209,407	)
Privately issued commercial		—		—			17,233		(3,861	)
Collateralized debt obligations		3,039		(19	)		5,544		(1,448	)
Other debt securities		51,652		(935	)		101,588		(27,079	)
Equity securities		3,375		(451	)		—		—
		840,819		(6,209	)		989,628		(241,872	)
Investment securities held to maturity:
Obligations of states and political subdivisions		22,591		(108	)		451		(41	)
Privately issued mortgage-backed securities		322		(123	)		184,970		(102,492	)
		22,913		(231	)		185,421		(102,533	)
Total	$	863,732		(6,440	)		1,175,049		(344,405	)

	Less than 12 months					12 months or more
			Unrealized					Unrealized
	Fair value		losses			Fair value		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	)