Investments (Tables)

3 Months Ended

Mar. 31, 2012

Investments [Abstract]

Available-For-Sale Investments

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Market Value
March 31, 2012
Money market investments	$	551	$	—	$	—	$	551
Mortgage-backed securities		2,934		109		—		3,043
Corporate bonds and direct obligations of government agencies		68,368		1,018		97		69,289
U.S. Treasury obligations		12,996		41		3		13,034
Total	$	84,849	$	1,168	$	100	$	85,917
December 31, 2011
Money market investments	$	1,989	$	—	$	—	$	1,989
Mortgage-backed securities		3,017		61		18		3,060
Corporate bonds and direct obligations of government agencies		51,014		819		126		51,707
U.S. Treasury obligations		11,682		51		1		11,732
Total	$	67,702	$	931	$	145	$	68,488

Schedule Of Unrealized Loss On Investments

	Less than 12 months				12 months or longer				Total
	Fair Market Value		Unrealized Loss		Fair Market Value		Unrealized Loss		Fair Market Value		Unrealized Loss
March 31, 2012
Corporate bonds and direct obligations of government agencies	$	14,956	$	97	$	—	$	—	$	14,956	$	97
U.S. Treasury obligations		11,286		3		—		—		11,286		3
Total	$	26,242	$	100	$	—	$	—	$	26,242	$	100
December 31, 2011
Mortgage-backed securities	$	468	$	18	$	—	$	—	$	468	$	18
Corporate bonds and direct obligations of government agencies		6,067		126		—		—		6,067		126
U.S. Treasury obligations		591		1		—		—		591		1
Total	$	7,126	$	145	$	—	$	—	$	7,126	$	145