3. 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)
March 31, 2014
Investment securities available for sale:
U.S. Treasury and federal agencies	$	42,415		291		59	$	42,647
Obligations of states and political subdivisions		10,148		306		71		10,383
Mortgage-backed securities:
Government issued or guaranteed		5,722,948		85,193		7,050		5,801,091
Privately issued		235		466		5		696
Collateralized debt obligations		38,451		23,623		306		61,768
Other debt securities		138,197		1,859		17,807		122,249
Equity securities		89,669		63,431		363		152,737

		6,042,063		175,169		25,661		6,191,571

Investment securities held to maturity:
Obligations of states and political subdivisions		162,894		3,280		194		165,980
Mortgage-backed securities:
Government issued or guaranteed		3,486,786		26,847		37,718		3,475,915
Privately issued		215,649		—		51,434		164,215
Other debt securities		8,656		—		—		8,656

		3,873,985		30,127		89,346		3,814,766

Other securities		298,693		—		—		298,693

Total	$	10,214,741		205,296		115,007	$	10,305,030


	Amortized cost		Gross unrealized gains		Gross unrealized losses		Estimated fair value
	(in thousands)
December 31, 2013
Investment securities available for sale:
U.S. Treasury and federal agencies	$	37,396		382		2	$	37,776
Obligations of states and political subdivisions		10,484		333		6		10,811
Mortgage-backed securities:
Government issued or guaranteed		4,123,435		61,001		19,350		4,165,086
Privately issued		1,468		387		5		1,850
Collateralized debt obligations		42,274		21,666		857		63,083
Other debt securities		137,828		1,722		19,465		120,085
Equity securities		91,480		41,842		227		133,095

		4,444,365		127,333		39,912		4,531,786

Investment securities held to maturity:
Obligations of states and political subdivisions		169,684		3,744		135		173,293
Mortgage-backed securities:
Government issued or guaranteed		3,567,905		16,160		65,149		3,518,916
Privately issued		219,628		—		60,623		159,005
Other debt securities		8,913		—		—		8,913

		3,966,130		19,904		125,907		3,860,127

Other securities		298,581		—		—		298,581

Total	$	8,709,076		147,237		165,819	$	8,690,494

There were no gross realized gains or losses from sales of investment securities for the quarters ended March 31, 2014 and 2013. The Company recognized $10 million of pre-tax other-than-temporary impairment (“OTTI”) losses during the quarter ended March 31, 2013 related to privately issued mortgage-backed securities. The impairment charges were recognized in light of deterioration of real estate values and a rise in delinquencies and charge-offs of underlying mortgage loans collateralizing those securities. The OTTI losses represented management’s estimate of credit losses inherent in the debt securities considering projected cash flows using assumptions for delinquency rates, loss severities, and other estimates of future collateral performance. There were no OTTI losses during the first quarter of 2014.

Changes in credit losses associated with debt securities for which OTTI losses have been recognized in earnings for the three months ended March 31, 2013 follows:


	Three months ended March 31, 2013
	(in thousands)
Beginning balance	$	197,809
Additions for credit losses not previously recognized		9,800
Reductions for realized losses		(20,495	)

Ending balance	$	187,114

There were no significant credit losses associated with debt securities held by the Company as of March 31, 2014 or December 31, 2013.

At March 31, 2014, 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	$	9,830		9,957
Due after one year through five years		43,459		44,086
Due after five years through ten years		5,328		5,442
Due after ten years		170,594		177,562

		229,211		237,047
Mortgage-backed securities available for sale		5,723,183		5,801,787

	$	5,952,394		6,038,834

Debt securities held to maturity:
Due in one year or less	$	17,944		18,049
Due after one year through five years		74,928		76,540
Due after five years through ten years		70,022		71,391
Due after ten years		8,656		8,656

		171,550		174,636
Mortgage-backed securities held to maturity		3,702,435		3,640,130

	$	3,873,985		3,814,766

A summary of investment securities that as of March 31, 2014 and December 31, 2013 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)
March 31, 2014
Investment securities available for sale:
U.S. Treasury and federal agencies	$	29,346		(59	)		—		—
Obligations of states and political subdivisions		1,930		(68	)		439		(3	)
Mortgage-backed securities:
Government issued or guaranteed		1,725,859		(6,919	)		5,215		(131	)
Privately issued		—		—			91		(5	)
Collateralized debt obligations		—		—			6,097		(306	)
Other debt securities		927		(10	)		105,418		(17,797	)
Equity securities		2,307		(363	)		—		—

		1,760,369		(7,419	)		117,260		(18,242	)

Investment securities held to maturity:
Obligations of states and political subdivisions		17,490		(155	)		2,658		(39	)

Mortgage-backed securities:
Government issued or guaranteed		1,715,149		(37,718	)		—		—
Privately issued		—		—			164,215		(51,434	)

		1,732,639		(37,873	)		166,873		(51,473	)

Total	$	3,493,008		(45,292	)		284,133		(69,715	)

December 31, 2013
Investment securities available for sale:
U.S. Treasury and federal agencies	$	745		(2	)		—		—
Obligations of states and political subdivisions		—		—			558		(6	)
Mortgage-backed securities:
Government issued or guaranteed		1,697,094		(19,225	)		5,815		(125	)
Privately issued		—		—			98		(5	)
Collateralized debt obligations		—		—			6,257		(857	)
Other debt securities		1,428		(4	)		103,602		(19,461	)
Equity securities		159		(227	)		—		—

		1,699,426		(19,458	)		116,330		(20,454	)

Investment securities held to maturity:
Obligations of states and political subdivisions		13,517		(120	)		1,558		(15	)
Mortgage-backed securities:
Government issued or guaranteed		2,629,950		(65,149	)		—		—
Privately issued		—		—			159,005		(60,623	)

		2,643,467		(65,269	)		160,563		(60,638	)

Total	$	4,342,893		(84,727	)		276,893		(81,092	)

The Company owned 392 individual investment securities with aggregate gross unrealized losses of $115 million at March 31, 2014. Based on a review of each of the securities in the investment securities portfolio at March 31, 2014, the Company concluded that it expected to recover the amortized cost basis of its investment. As of March 31, 2014, the Company does not intend to sell nor is it anticipated that it would be required to sell any of its impaired investment securities at a loss. At March 31, 2014, the Company has not identified events or changes in circumstances which may have a significant adverse effect on the fair value of the $299 million of cost method investment securities.