Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 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):

	March31, 2013			December31, 2012
	Level 1	Level 2	Total		Level 1	Level 2	Total
Assets:
Cash and cash equivalents:
Money market funds	$57,879	$ —	$57,879		$23,119	$ —	$23,119
Commercial paper	—	24,297	24,297		—	38,582	38,582
Short-term investments:
Commercial paper	—	25,795	25,795		—	32,100	32,100
U.S. government agency bonds	—	750	750		—	748	748
Total	$57,879	$50,842	$108,721		$23,119	$71,430	$94,549
Liabilities:
Interest rate swap contracts (1)	$ —	$896	$896		$ —	$1,069	$1,069
Total	$ —	$896	$896		$ —	$1,069	$1,069

(1)As of March31, 2013, the fair valueof 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 (in millions):

	March31, 2013		December31,2012
	Carrying Value	Fair Value	Carrying Value	Fair Value
Credit Agreement (carrying value including current maturities)	$146	$158	$150	$163
Convertible debt (par value)	150	167	150	158