Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2011

Marketable Securities (Tables) [Abstract]

Company's marketable securities

			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		Losses			Fair Value
June 30, 2011
Debt securities:
Municipal securities	$	314,125	$	671	$	(406	)	$	314,390
Equity securities		50,000		—		(11,664	)		38,336
Total marketable securities	$	364,125	$	671	$	(12,070	)	$	352,726
December 31, 2010
Debt securities:
Treasury securities	$	7,937	$	11	$	(57	)	$	7,891
Municipal securities		368,583		550		(2,833	)		366,300
Corporate debt securities		3,722		—		(78	)		3,644
Equity securities		50,000		2,130		—			52,130
Total marketable securities	$	430,242	$	2,691	$	(2,968	)	$	429,965

Estimated fair values and gross unrealized losses for the Companys investments in individual securities

Less than 12 Months					More than 12 Months
Estimated Fair		Unrealized			Estimated Fair		Unrealized
Value		Losses			Value		Losses
$	140,227	$	(12,070	)	$	—	$	—

Current And Non Current Classification Of Marketable Securities

	June 30,		December 31,
	2011		2010
Current	$	212,499	$	170,648
Non-current		140,227		259,317
Total marketable securities	$	352,726	$	429,965

Gross realized gains and losses from sale of marketable securities

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2011		2010		2011			2010
Proceeds from sale of marketable securities	$	195,025	$	144,684	$	225,178		$	285,265
Gross realized gains	$	2,110	$	1,855	$	2,112		$	4,082
Gross realized losses		—		—		(356	)		—
Net realized gain	$	2,110	$	1,855	$	1,756		$	4,082