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)
December 31, 2014
Investment securities available for sale:
U.S. Treasury and federal agencies	$	161,408	$	544	$	5	$	161,947
Obligations of states and political subdivisions		8,027		224		53		8,198
Mortgage-backed securities:
Government issued or guaranteed		8,507,571		223,889		337		8,731,123
Privately issued		104		2		3		103
Collateralized debt obligations		30,073		21,276		1,033		50,316
Other debt securities		138,240		1,896		18,648		121,488
Equity securities		73,901		11,020		1,164		83,757

		8,919,324		258,851		21,243		9,156,932

Investment securities held to maturity:
Obligations of states and political subdivisions		148,961		2,551		189		151,323
Mortgage-backed securities:
Government issued or guaranteed		3,149,320		78,485		7,000		3,220,805
Privately issued		201,733		1,143		44,576		158,300
Other debt securities		7,854		—		—		7,854

		3,507,868		82,179		51,765		3,538,282

Other securities		328,742		—		—		328,742

Total	$	12,755,934	$	341,030	$	73,008	$	13,023,956

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

No investment in securities of a single non-U.S. Government or government agency issuer exceeded ten percent of shareholders’ equity at December 31, 2014.

As of December 31, 2014, 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
	Amortized Cost		Estimated Fair Value		A or Better		BBB		BB		B or Less		Not Rated
	(In thousands)
Obligations of states and political subdivisions	$	156,988	$	159,521	$	137,606	$	—	$	—	$	—	$	21,915
Privately issued mortgage-backed securities		201,837		158,403		48,368		19		—		109,949		67
Collateralized debt obligations		30,073		50,316		6,629		5,488		1,273		36,926		—
Other debt securities		146,094		129,342		12,352		58,481		29,028		20,400		9,081

Total	$	534,992	$	497,582	$	204,955	$	63,988	$	30,301	$	167,275	$	31,063

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


	December 31
	2014		2013
	(In thousands)
Collateralized mortgage obligations:
Amortized cost	$	209,107	$	231,040
Estimated fair value		165,860		171,100

Gross realized gains from sales of investment securities were $116,490,000 in 2013. During 2013, the Company sold its holdings of Visa Class B shares for a gain of $89,545,000 and its holdings of MasterCard Class B shares for a gain of $13,208,000. Gross realized losses on investment securities were $60,033,000 in 2013. The Company sold substantially all of its privately issued mortgage-backed securities held in the available-for-sale investment securities portfolio during 2013. In total, $1.0 billion of such securities were sold for a net loss of approximately $46,302,000. Gross realized gains and losses from sales of investment securities were not significant in 2014 or 2012.

The Company recognized $10 million and $48 million of pre-tax other-than-temporary impairment losses related to privately issued mortgage-backed securities in 2013 and 2012, respectively. 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 other-than-temporary impairment 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 other-than-temporary impairment losses in 2014.

At December 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	$	7,412	$	7,468
Due after one year through five years		164,412		165,340
Due after five years through ten years		3,524		3,577
Due after ten years		162,400		165,564

		337,748		341,949
Mortgage-backed securities available for sale		8,507,675		8,731,226

	$	8,845,423	$	9,073,175

Debt securities held to maturity:
Due in one year or less	$	23,107	$	23,254
Due after one year through five years		84,112		85,457
Due after five years through ten years		41,742		42,612
Due after ten years		7,854		7,854

		156,815		159,177
Mortgage-backed securities held to maturity		3,351,053		3,379,105

	$	3,507,868	$	3,538,282

A summary of investment securities that as of December 31, 2014 and 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)
December 31, 2014
Investment securities available for sale:
U.S. Treasury and federal agencies	$	6,505	$	(5	)	$	—	$	—
Obligations of states and political subdivisions		1,785		(52	)		121		(1	)
Mortgage-backed securities:
Government issued or guaranteed		39,001		(186	)		5,555		(151	)
Privately issued		—		—			65		(3	)
Collateralized debt obligations		2,108		(696	)		5,512		(337	)
Other debt securities		14,017		(556	)		92,661		(18,092	)
Equity securities		2,138		(1,164	)		—		—

		65,554		(2,659	)		103,914		(18,584	)

Investment securities held to maturity:
Obligations of states and political subdivisions		29,886		(184	)		268		(5	)
Mortgage-backed securities:
Government issued or guaranteed		137,413		(361	)		446,780		(6,639	)
Privately issued		—		—			127,512		(44,576	)

		167,299		(545	)		574,560		(51,220	)

Total	$	232,853	$	(3,204	)	$	678,474	$	(69,804	)

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 296 individual investment securities with aggregate gross unrealized losses of $73 million at December 31, 2014. Based on a review of each of the securities in the investment securities portfolio at December 31, 2014, the Company concluded that it expected to recover the amortized cost basis of its investment. As of December 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 December 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 $329 million of cost method investment securities.

At December 31, 2014, investment securities with a carrying value of $3,825,003,000, including $2,905,457,000 of investment securities available for sale, were pledged to secure borrowings from various FHLBs, repurchase agreements, governmental deposits, interest rate swap agreements and available lines of credit as described in note 9.

Investment securities pledged by the Company to secure obligations whereby the secured party is permitted by contract or custom to sell or repledge such collateral totaled $1,631,267,000 at December 31, 2014. The pledged securities included securities of the U.S. Treasury and federal agencies and mortgage-backed securities.