Investments (Tables)

9 Months Ended

Sep. 30, 2011

Investments [Abstract]

Available-For-Sale Investments

	As of:
	September 30, 2011						December 31, 2010						September 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 (Losses)
Available-for-Sale Investments:
Government obligations		$90,629		$90,611		$18		$110,560		$110,550		$10		$90,374		$90,348		$26
Government agency obligations		31,565		31,565		0		24,394		24,399		(5)		36,165		36,153		12
Corporate obligations		24,605		24,645		(40)		8,903		8,908		(5)		10,683		10,688		(5)
		$146,799		$146,821		($22)		$143,857		$143,857		$0		$ 137,222		$ 137,189		$ 33

Unrealized Gains And Losses On Available-For-Sale Investments

	Three Months Ended          September 30,				Nine Months Ended          September 30,
	2011		2010		2011		2010
Unrealized gains		$0		$0		$0		$56
Unrealized losses		($15)		($14)		($102)		$0

Components Of Investment Income

		0000		0000		0000		0000	0000	0000
	Three Months  Ended September 30,				Nine Months  Ended September 30,
	2011		2010		2011		2010
Interest income on investments		$91		$188		$362		$551
Realized net gains on the sale of investments		23		51		219		150
		$114		$239		$581		$701