Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2013

Fair Value Measurements

The following table represents the fair value hierarchy based upon three levels of inputs, of which Levels 1 and 2 are considered observable and Level 3 is unobservable, for financial assets and liabilities measured at fair value on a recurring basis (in thousands):

	June 30, 2013								December31, 2012
	Level 1		Level 2			Total			Level 1			Level 2			Total
Assets:
Cash equivalents:
Money market funds	$	32,378		$	—		$	32,378		$	23,119		$	—		$	23,119
Commercial paper		—			14,395			14,395			—			35,856			35,856
Short-term investments:
Money market funds		—			2,351			2,351
Commercial paper		—			44,290			44,290			—			34,826			34,826
Municipal bonds		—			29,560			29,560			—			—			—
U.S. government agency bonds		—			16,244			16,244			—			748			748
Total	$	32,378		$	106,840		$	139,218		$	23,119		$	71,430		$	94,549
Liabilities:
Interest rate swap contracts (1)	$	—		$	628		$	628		$	—		$	1,069		$	1,069
Total	$	—		$	628		$	628		$	—		$	1,069		$	1,069

(1)As of June30, 2013, the fair value of the interest rate swap contract was classified on our Balance Sheet in “Other current liabilities”. As of December31, 2012, the fair value of the interest rate swap contracts were classified on our Balance Sheet in “Other non-current liabilities”.

Carrying Value and Estimated Fair Value of Debt

The following table indicates the carrying value and estimated fair value of our debt as of the indicated periods (inthousands):

	June30, 2013						December31,2012
	Carrying Value		Fair Value			Carrying Value				Fair Value
Credit Agreement (carrying value including current maturities)	$	142,500		$	150,468			$	150,000		$	162,881
Convertible debt (par value)		150,000			166,932				150,000			158,400