Investment securities (Tables)

12 Months Ended

Dec. 31, 2012

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)
December 31, 2012
Investment securities available for sale:
U.S. Treasury and federal agencies	$	38,422	$	922	$	—	$	39,344
Obligations of states and political subdivisions		20,375		534		8		20,901
Mortgage-backed securities:
Government issued or guaranteed		3,163,210		208,060		229		3,371,041
Privately issued residential		1,133,639		4,894		125,647		1,012,886
Privately issued commercial		8,648		2,378		26		11,000
Collateralized debt obligations		43,228		19,663		1,022		61,869
Other debt securities		136,603		2,247		26,900		111,950
Equity securities		98,945		14,921		3,420		110,446
		4,643,070		253,619		157,252		4,739,437
Investment securities held to maturity:
Obligations of states and political subdivisions		182,103		7,647		27		189,723
Mortgage-backed securities:
Government issued or guaranteed		597,340		31,727		—		629,067
Privately issued		242,378		160		94,900		147,638
Other debt securities		10,455		—		—		10,455
		1,032,276		39,534		94,927		976,883
Other securities		302,648		—		—		302,648
Total	$	5,977,994	$	293,153	$	252,179	$	6,018,968
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

Investment Ratings of All Privately Issued Mortgage-Backed Securities, Collateralized Debt Obligations and Other Debt Securities

As of December 31, 2012, the latest available investment ratings of all obligations of states and political subdivisions, privately issued mortgage-backed securities, collateralized debt obligations and other debt securities were:

	Amortized Cost		Estimated Fair Value		Average Credit Rating of Fair Value Amount
					A or Better		BBB		BB		B or Less		Not Rated
	(In thousands)
Obligations of states and political subdivisions	$	202,478	$	210,624	$	169,660	$	7,215	$	200	$	—	$	33,549
Mortgage-backed securities:
Privately issued residential		1,376,017		1,160,524		206,479		87,866		151,980		712,765		1,434
Privately issued commercial		8,648		11,000		—		—		—		11,000		—
Collateralized debt obligations		43,228		61,869		4,268		10,298		10,770		36,533		—
Other debt securities		147,058		122,405		11,852		57,387		27,029		14,532		11,605
Total	$	1,777,429	$	1,566,422	$	392,259	$	162,766	$	189,979	$	774,830	$	46,588

Amortized Cost and Estimated Fair Value of Collateralized Mortgage Obligations

The amortized cost and estimated fair value of collateralized mortgage obligations included in mortgage-backed securities were as follows:

	December 31
	2012		2011
	(In thousands)
Collateralized mortgage obligations:
Amortized cost	$	1,414,691	$	1,750,922
Estimated fair value		1,202,243		1,417,822

Changes in Credit Losses Associated with Debt Securities for Which Other-Than-Temporary Impairment Losses

Changes in credit losses during 2012, 2011 and 2010 associated with debt securities for which other-than-temporary impairment losses have been recognized in earnings follows:

	Year Ended December 31
	2012			2011			2010
	(In thousands)
Estimated credit losses — beginning balance	$	285,399		$	327,912		$	284,513
Additions for credit losses not previously recognized		47,822			77,035			74,288
Reductions for increases in cash flows		—			(5,111	)		(754	)
Reductions for realized losses		(135,412	)		(114,437	)		(30,135	)
Estimated credit losses — ending balance	$	197,809		$	285,399		$	327,912

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

At December 31, 2012, 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	$	4,918	$	4,952
Due after one year through five years		41,800		43,139
Due after five years through ten years		9,524		10,217
Due after ten years		182,386		175,756
		238,628		234,064
Mortgage-backed securities available for sale		4,305,497		4,394,927
	$	4,544,125	$	4,628,991
Debt securities held to maturity:
Due in one year or less	$	26,716	$	26,850
Due after one year through five years		50,310		52,526
Due after five years through ten years		104,901		110,167
Due after ten years		10,631		10,635
		192,558		200,178
Mortgage-backed securities held to maturity		839,718		776,705
	$	1,032,276	$	976,883

Investment Securities in Continuous Unrealized Loss Position

A summary of investment securities that as of December 31, 2012 and 2011 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)
December 31, 2012
Investment securities available for sale:
Obligations of states and political subdivisions	$	166	$	(1	)	$	683	$	(7	)
Mortgage-backed securities:
Government issued or guaranteed		12,107		(65	)		8,804		(164	)
Privately issued residential		121,487		(692	)		773,409		(124,955	)
Privately issued commercial		—		—			919		(26	)
Collateralized debt obligations		—		—			6,043		(1,022	)
Other debt securities		—		—			95,685		(26,900	)
Equity securities		5,535		(1,295	)		2,956		(2,125	)
		139,295		(2,053	)		888,499		(155,199	)
Investment securities held to maturity:
Obligations of states and political subdivisions		1,026		(5	)		3,558		(22	)
Privately issued mortgage-backed securities		—		—			147,273		(94,900	)
		1,026		(5	)		150,831		(94,922	)
Total	$	140,321	$	(2,058	)	$	1,039,330	$	(250,121	)
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	)