Fair Value Measurement (Tables)

6 Months Ended

Jun. 30, 2012

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

The following tables summarize each class of assets and liabilities measured at fair value on a recurring basis as well as assets and liabilities that are disclosed but not recorded at fair value: 

June 30, 2012	Fair Value Measurement at Reporting Date Using
(in thousands)	Level 11		Level 22		Level 33		Total
Cash equivalents
Money market funds	$	167,427	$	—	$	—	$	167,427
Marketable securities
Held-to-maturity marketable securities	89,239		—		—		89,239
Total assets	$	256,666	$	—	$	—	$	256,666
Long-term debt (including current maturities)
Senior notes payable	$	—	$	—	$	239,443	$	239,443
Total liabilities	$	—	$	—	$	239,443	$	239,443

December 31, 2011	Fair Value Measurement at Reporting Date Using
(in thousands)	Level 11		Level 22		Level 33		Total
Cash equivalents
Money market funds	$	178,174	$	—	$	—	$	178,174
Marketable securities
Held-to-maturity marketable securities	149,979		—		—		149,979
Total assets	$	328,153	$	—	$	—	$	328,153
Long-term debt (including current maturities)
Senior notes payable	$	—	$	—	$	250,541	$	250,541
Total liabilities	$	—	$	—	$	250,541	$	250,541

June 30, 2011	Fair Value Measurement at Reporting Date Using
(in thousands)	Level 11		Level 22		Level 33		Total
Cash equivalents
Money market funds	$	163,058	$	—	$	—	$	163,058
Marketable securities
Held-to-maturity marketable securities	128,263		—		—		128,263
Total assets	$	291,321	$	—	$	—	$	291,321
Long-term debt (including current maturities)
Senior notes payable	$	—	$	—	$	239,641	$	239,641
Total liabilities	$	—	$	—	$	239,641	$	239,641

¹Quoted prices in active markets for identical assets or liabilities.

²Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

³Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

Schedule of Cash and Cash Equivalents [Table Text Block]

A reconciliation of money market funds to consolidated cash and cash equivalents is as follows:

(in thousands)	June 30, 2012		December 31, 2011		June 30, 2011
Money market funds	$	167,427	$	178,174	$	163,058
Held-to-maturity commercial paper	4,997		4,999		—
Cash	65,527		73,817		27,011
Total cash and cash equivalents	$	237,951	$	256,990	$	190,069