Fair Value Measurement (Tables)

3 Months Ended

Mar. 31, 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: 

March 31, 2012	Fair Value Measurement at Reporting Date Using
(in thousands)	Level 11		Level 22		Level 33		Total
Cash equivalents
Money market funds	$	157,034	$	—	$	—	$	157,034
Marketable securities
Held-to-maturity marketable securities	140,728		—		—		140,728
Total assets	$	297,762	$	—	$	—	$	297,762
Long-term debt (including current maturities)
Senior notes payable	$	—	$	—	$	246,600	$	246,600
Total liabilities	$	—	$	—	$	246,600	$	246,600

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

March 31, 2011	Fair Value Measurement at Reporting Date Using
(in thousands)	Level 11		Level 22		Level 33		Total
Cash equivalents
Money market funds	$	197,714	$	—	$	—	$	197,714
Marketable securities
Held-to-maturity marketable securities	129,815		—		—		129,815
Total assets	$	327,529	$	—	$	—	$	327,529
Long-term debt (including current maturities)
Senior notes payable	$	—	$	—	$	242,524	$	242,524
Total liabilities	$	—	$	—	$	242,524	$	242,524

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)	March 31, 2012		December 31, 2011		March 31, 2011
Money market funds	$	157,034	$	178,174	$	197,714
Held-to-maturity commercial paper	4,997		4,999		14,993
Cash	64,195		73,817		28,061
Total cash and cash equivalents	$	226,226	$	256,990	$	240,768