Investment securities (Tables)

6 Months Ended

Jun. 30, 2012

Investment securities [Abstract]

Amortized cost and estimated fair value of investment securities

	Amortized cost		Gross unrealized gains		Gross unrealized losses		Estimated fair value
	(in thousands)
June 30, 2012
Investment securities available for sale:
U.S. Treasury and federal agencies	$	55,484		1,115		—	$	56,599
Obligations of states and political subdivisions		34,007		569		8		34,568
Mortgage-backed securities:
Government issued or guaranteed		3,840,610		218,117		227		4,058,500
Privately issued residential		1,252,709		5,254		189,571		1,068,392
Privately issued commercial		13,048		—		921		12,127
Collateralized debt obligations		43,749		13,079		1,730		55,098
Other debt securities		158,153		2,034		31,258		128,929
Equity securities		112,337		10,926		3,422		119,841
		5,510,097		251,094		227,137		5,534,054
Investment securities held to maturity:
Obligations of states and political subdivisions		187,936		8,375		30		196,281
Mortgage-backed securities:
Government issued or guaranteed		733,912		31,929		—		765,841
Privately issued		255,291		317		97,220		158,388
Other debt securities		11,326		—		—		11,326
		1,188,465		40,621		97,250		1,131,836
Other securities		334,781		—		—		334,781
Total	$	7,033,343		291,715		324,387	$	7,000,671
December 31, 2011
Investment securities available for sale:
U.S. Treasury and federal agencies	$	69,468		1,255		—	$	70,723
Obligations of states and political subdivisions		39,518		771		20		40,269
Mortgage-backed securities:
Government issued or guaranteed		4,344,116		177,392		275		4,521,233
Privately issued residential		1,369,371		6,373		239,488		1,136,256
Privately issued commercial		17,679		—		2,650		15,029
Collateralized debt obligations		43,834		11,154		2,488		52,500
Other debt securities		216,700		4,588		44,443		176,845
Equity securities		211,737		8,468		4,500		215,705
		6,312,423		210,001		293,864		6,228,560
Investment securities held to maturity:
Obligations of states and political subdivisions		188,680		9,141		28		197,793
Mortgage-backed securities:
Government issued or guaranteed		608,533		24,881		—		633,414
Privately issued		268,642		—		99,140		169,502
Other debt securities		11,853		—		—		11,853
		1,077,708		34,022		99,168		1,012,562
Other securities		366,886		—		—		366,886
Total	$	7,757,017		244,023		393,032	$	7,608,008

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

	Three months ended June 30
	2012			2011
	(in thousands)
Beginning balance	$	267,473			322,719
Additions for credit losses not previously recognized		16,173			26,530
Reductions for increases in cash flows		—			(4,881	)
Reductions for realized losses		(19,449	)		(46,227	)
Ending balance	$	264,197			298,141
	Six months ended June 30
	2012			2011
	(in thousands)
Beginning balance	$	285,399			327,912
Additions for credit losses not previously recognized		27,659			42,571
Reductions for increases in cash flows		—			(5,020	)
Reductions for realized losses		(48,861	)		(67,322	)
Ending balance	$	264,197			298,141

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

	Amortized cost		Estimated fair value
	(in thousands)
Debt securities available for sale:
Due in one year or less	$	33,314		33,367
Due after one year through five years		40,715		42,082
Due after five years through ten years		11,098		11,886
Due after ten years		206,266		187,859
		291,393		275,194
Mortgage-backed securities available for sale		5,106,367		5,139,019
	$	5,397,760		5,414,213
Debt securities held to maturity:
Due in one year or less	$	30,983		31,166
Due after one year through five years		40,576		42,599
Due after five years through ten years		114,797		120,839
Due after ten years		12,906		13,003
		199,262		207,607
Mortgage-backed securities held to maturity		989,203		924,229
	$	1,188,465		1,131,836

Investment securities in continuous unrealized loss position

	Less than 12 months					12 months or more
	Fair value		Unrealized losses			Fair value		Unrealized losses
	(in thousands)
June 30, 2012
Investment securities available for sale:
Obligations of states and political subdivisions	$	171		(1	)		678		(7	)
Mortgage-backed securities:
Government issued or guaranteed		15,936		(70	)		9,951		(157	)
Privately issued residential		126,139		(1,861	)		841,748		(187,710	)
Privately issued commercial		—		—			12,127		(921	)
Collateralized debt obligations		3,106		(39	)		5,349		(1,691	)
Other debt securities		16,858		(2,053	)		74,206		(29,205	)
Equity securities		8,118		(1,389	)		2,193		(2,033	)
		170,328		(5,413	)		946,252		(221,724	)
Investment securities held to maturity:
Obligations of states and political subdivisions		5,598		(23	)		169		(7	)
Privately issued mortgage-backed securities		—		—			157,659		(97,220	)
		5,598		(23	)		157,828		(97,227	)
Total	$	175,926		(5,436	)		1,104,080		(318,951	)
December 31, 2011
Investment securities available for sale:
Obligations of states and political subdivisions	$	—		—			1,228		(20	)
Mortgage-backed securities:
Government issued or guaranteed		38,492		(190	)		6,017		(85	)
Privately issued residential		297,133		(14,188	)		751,077		(225,300	)
Privately issued commercial		—		—			15,029		(2,650	)
Collateralized debt obligations		2,871		(335	)		4,863		(2,153	)
Other debt securities		72,637		(9,883	)		73,635		(34,560	)
Equity securities		9,883		(4,500	)		—		—
		421,016		(29,096	)		851,849		(264,768	)
Investment securities held to maturity:
Obligations of states and political subdivisions		3,084		(4	)		1,430		(24	)
Privately issued mortgage-backed securities		1,883		(592	)		167,139		(98,548	)
		4,967		(596	)		168,569		(98,572	)
Total	$	425,983		(29,692	)		1,020,418		(363,340	)