INVESTMENTS

The Company considers all of its investments as available-for-sale securities. Realized gains and losses on the sale of investments are determined on a specific identification basis.

The amortized cost, gross unrealized gain or loss and estimated fair value of short-term and long-term investments by security type were as follows as of March 31, 2013 and December 31, 2012 (in thousands):



	Amortized Cost		Unrealized Gain		Unrealized Loss			Fair Value
As of March 31, 2013
State and municipal bonds	$	1,120,913	$	66,748	$	(726	)	$	1,186,935
U.S. Treasury securities	114,448		577		(1		)	115,024
Government-sponsored enterprise securities	79,039		248		(2		)	79,285
Residential mortgage-backed securities ⁽¹⁾	328,940		9,051		(793		)	337,198
Commercial mortgage-backed securities	33,938		80		(126		)	33,892
Asset-backed securities ⁽²⁾	22,226		356		(10		)	22,572
Corporate debt and other securities	1,022,287		13,284		(559		)	1,035,012
	$	2,721,791	$	90,344	$	(2,217	)	$	2,809,918
Equity method investments ⁽³⁾								24,118
								$	2,834,036



	Amortized Cost		Unrealized Gain		Unrealized Loss			Fair Value
As of December 31, 2012
State and municipal bonds	$	1,176,016	$	78,272	$	(499	)	$	1,253,789
U.S. Treasury securities	78,264		669		(2		)	78,931
Government-sponsored enterprise securities	72,394		1,139		(1		)	73,532
Residential mortgage-backed securities ⁽¹⁾	302,012		10,703		(74		)	312,641
Commercial mortgage-backed securities	21,416		193		(19		)	21,590
Asset-backed securities⁽²⁾	23,421		211		(6		)	23,626
Corporate debt and other securities	971,230		20,726		(346		)	991,610
	$	2,644,753	$	111,913	$	(947	)	$	2,755,719
Equity method investments⁽³⁾								24,605
								$	2,780,324


⁽¹⁾	Includes Agency pass-through securities, with the timely payment of principal and interest guaranteed.


⁽²⁾	Includes auto loans, credit card debt, and rate reduction bonds.


⁽³⁾	Includes investments in entities accounted for under the equity method of accounting and therefore are presented at their carrying value.

The amortized cost and estimated fair value of available-for-sale debt securities by contractual maturity were as follows as of March 31, 2013 and December 31, 2012 (in thousands):



	As of March 31, 2013				As of December 31, 2012
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Maturities:
Within 1 year	$	468,436	$	470,166	$	362,116	$	363,559
1 to 5 years	725,945		747,376		798,143		822,448
5 to 10 years	711,930		745,058		652,941		693,504
Over 10 years	815,480		847,318		831,553		876,208
Total	$	2,721,791	$	2,809,918	$	2,644,753	$	2,755,719

Investments with long-term option adjusted maturities, such as residential and commercial mortgage-backed securities, are included in the “Over 10 years” category. Actual maturities may differ due to call or prepayment rights.

Gross investment gains of $12.8 million and $0.3 million gross investment losses were realized on sales of investments for the quarter ended March 31, 2013. This compares to gross investment gains of $4.3 million and no gross investment losses realized on sales of investments for the quarter ended March 31, 2012. All realized gains and losses are recorded in other income, net in the Company’s consolidated statements of operations and comprehensive income.

The following table shows the Company’s investments’ gross unrealized losses and fair value at March 31, 2013 and December 31, 2012, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position (in thousands):



	Less than 12 months					12 months or more					Total
At March 31, 2013	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
State and municipal bonds	$	110,627	$	(725	)	$	102	$	(1	)	$	110,729	$	(726	)
U.S. Treasury securities	1,774		(1		)	—		—			1,774		(1		)
Government-sponsored enterprise securities	11,786		(2		)	—		—			11,786		(2		)
Residential mortgage-backed securities	120,987		(792		)	60		(1		)	121,047		(793		)
Commercial mortgage-backed securities	21,456		(126		)	—		—			21,456		(126		)
Asset-backed securities	13,988		(10		)	—		—			13,988		(10		)
Corporate debt and other securities	94,947		(557		)	52		(2		)	94,999		(559		)
Total	$	375,565	$	(2,213	)	$	214	$	(4	)	$	375,779	$	(2,217	)



	Less than 12 months					12 months or more					Total
At December 31, 2012	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
State and municipal bonds	$	61,342	$	(499	)	$	—	$	—		$	61,342	$	(499	)
U.S. Treasury securities	2,458		(1		)	1,065		(1		)	3,523		(2		)
Government-sponsored enterprise securities	15,714		(1		)	—		—			15,714		(1		)
Residential mortgage-backed securities	23,861		(73		)	59		(1		)	23,920		(74		)
Commercial mortgage-backed securities	7,701		(19		)	—		—			7,701		(19		)
Asset-backed securities	14,492		(6		)	—		—			14,492		(6		)
Corporate debt and other securities	79,381		(345		)	614		(1		)	79,995		(346		)
Total	$	204,949	$	(944	)	$	1,738	$	(3	)	$	206,687	$	(947	)

The unrealized losses presented in the table above do not meet the criteria for treatment as an other-than-temporary impairment. The unrealized losses are the result of, among other factors, interest rate movements. The Company has not decided to sell, and it is not more-likely-than-not that the Company will be required to sell before a recovery of the amortized cost basis of these securities.

The Company continues to review its investment portfolios under its impairment review policy. Given the current market conditions and the significant judgments involved, there is a continuing risk that declines in fair value may occur and that other-than-temporary impairments may be recorded in future periods.