Investments (Tables)

6 Months Ended

Jun. 30, 2011

Investments

Available-for-Sale Investments

	As of:
	June 30, 2011						December 31, 2010						June 30, 2010
	Aggregate Fair Value		Amortized Cost		Net Unrealized Gains (Losses)		Aggregate Fair Value		Amortized Cost		Net Unrealized Gains (Losses)		Aggregate Fair Value		Amortized Cost		Net Unrealized Gains
Available- for-Sale Investments:
Government obligations		$100,679		$100,664		$15		$110,560		$110,550		$10		$90,440		$90,416		$24
Government agency obligations		26,235		26,237		(2)		24,394		24,399		(5)		31,644		31,628		16
Corporate obligations		20,222		20,241		(19)		8,903		8,908		(5)		12,182		12,175		7
		$147,136		$147,142		($6)		$143,857		$143,857		$0		$134,266		$134,219		$47

Unrealized Gains and Losses on Available-for-Sale Investments

	Three Months Ended June 30,				Six Months Ended June 30,
	2011		2010		2011			2010
Unrealized gains		$46		$62		$0			$70
Unrealized losses		$0		$0		($87	)		$0

Components of Investment Income

	Three Months Ended June 30,				Six Months Ended June 30,
	2011		2010		2011		2010
Interest income on investments		$116		$213		$271		$366
Realized net gains on the sale of investments		51		6		196		99
		$167		$219		$467		$465