Fair Value Measurement (Tables)

3 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

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

The following tables summarize assets and liabilities measured at fair value in the condensed consolidated balance sheets on a recurring basis for each of the fair value levels (in thousands):

March 31, 2014	Fair Value Measurement at Reporting Date Using
	Level 1		Level 2		Level 3		Total
Cash equivalents
Money market funds	$	49,770	$	—	$	—	$	49,770
Total assets	$	49,770	$	—	$	—	$	49,770

December 31, 2013	Fair Value Measurement at Reporting Date Using
	Level 1		Level 2		Level 3		Total
Cash equivalents
Money market funds	$	89,336	$	—	$	—	$	89,336
Total assets	$	89,336	$	—	$	—	$	89,336

March 31, 2013	Fair Value Measurement at Reporting Date Using
	Level 1		Level 2		Level 3		Total
Cash equivalents
Money market funds	$	160,845	$	—	$	—	$	160,845
Held-to-maturity commercial paper	4,999		—		—		4,999
Total assets	$	165,844	$	—	$	—	$	165,844

Schedule of Cash and Cash Equivalents [Table Text Block]

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

(in thousands)	March 31, 2014		December 31, 2013		March 31, 2013
Cash equivalents	$	49,770	$	89,336	$	165,844
Cash	156,010		139,785		94,929
Total cash and cash equivalents	$	205,780	$	229,121	$	260,773

Fair Value Measurements, Nonrecurring [Table Text Block]

The carrying values and estimated fair values of our financial instruments that are not required to be recorded at fair value in the condensed consolidated balance sheets are as follows: 

		March 31, 2014				December 31, 2013				March 31, 2013
(in thousands)	Fair Value Hierarchy	Carrying Value		Fair Value		Carrying Value		Fair Value		Carrying Value		Fair Value
Assets:
Held-to-maturity marketable securities1	Level 1	$	107,112	$	106,864	$	117,202	$	116,915	$	102,799	$	102,872
Liabilities (including current maturities):
Senior notes payable2	Level 3	$	200,000	$	226,503	$	200,000	$	225,865	$	208,333	$	242,071
Credit Agreement loan2	Level 3	70,000		69,368		70,000		69,601		70,000		70,568

¹Held-to-maturity marketable securities are periodically assessed for other-than-temporary impairment.

²The fair values of the senior notes payable and Credit Agreement (defined in Note 10) loan are based on borrowing rates available to us for long-term loans with similar terms, average maturities, and credit risk.