Fair Value Measurements

6 Months Ended

Jun. 30, 2012

Fair Value Measurements [Abstract]

Fair Value Measurements [Text Block]

6.   Fair Value Measurements

The Company's assets that are measured at fair value on a recurring basis, at June 30, 2012 and December 31, 2011, were as follows:

		Fair Value Measurements at Reporting Date Using
	Fair Value	Quoted Prices in Active Markets for Identical Assets (Level 1)	Significant Other Observable Inputs (Level 2)	Significant Unobservable Inputs (Level 3)
At June 30, 2012
Unrestricted
Available-for-sale marketable securities:
U.S. government obligations	$351,788		$351,788
U.S. government guaranteed corporate bonds	50,654		50,654
Municipal bonds	12,386		12,386
Mortgage-backed securities	117		117
Equity security	2,455	$2,455
	417,400	2,455	414,945
Restricted
Available-for-sale marketable securities:
U.S. government obligations	8,044		8,044
	$425,444	$2,455	$422,989

At December 31, 2011
Unrestricted
Available-for-sale marketable securities:
U.S. government obligations	$284,819			$284,819
U.S. government guaranteed corporate bonds	15,316			15,316
U.S. government guaranteed collateralized mortgage obligations	622			622
Municipal bonds	15,326			15,326
Mortgage-backed securities	115			115
Equity security	3,019		$3,019
	319,217		3,019	316,198
Restricted
Available-for-sale marketable   securities:
U.S. government obligations		5,940		5,940
		$325,157	$3,019	$322,138

Marketable securities included in Level 2 were valued using a market approach utilizing prices and other relevant information, such as interest rates, yield curves, prepayment speeds, loss severities, credit risks and default rates, generated by market transactions involving identical or comparable assets.  The Company considers market liquidity in determining the fair value for these securities.  The Company did not record any charges for other-than-temporary impairment of its Level 2 marketable securities during the three and six months ended June 30, 2012 and 2011.

The Company holds one Level 3 marketable security, which had a fair value of $0 at June 30, 2012 and December 31, 2011.  This Level 3 security was valued using information provided by the Company's investment advisors and other sources, including quoted bid prices which took into consideration the security's lack of liquidity.  There were no purchases, sales, or maturities of Level 3 marketable securities and no unrealized gains or losses related to Level 3 marketable securities for the three months and six months ended June 30, 2012 and 2011.  There were no transfers of marketable securities between Levels 1, 2, or 3 classifications during the three and six months ended June 30, 2012 and 2011.

As of June 30, 2012, the Company had $400.0 million in aggregate principal amount of 1.875% convertible senior notes that will mature on October 1, 2016 unless earlier converted or repurchased.  The fair value of the outstanding convertible senior notes was estimated to be $605.8 million as of June 30, 2012, and was determined based on quoted market rates.