Fair Value Measurement (Tables)

6 Months Ended

Jun. 30, 2018

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following tables summarize significant 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):

	Fair Value Measurement at Reporting Date Using
June 30, 2018	Level 1		Level 2		Level 3		Total
Cash equivalents
Money market funds	$	56,534	$	—	$	—	$	56,534
Other noncurrent assets
Restricted cash		5,746		—		—		5,746
Total assets	$	62,280	$	—	$	—	$	62,280
December 31, 2017
Cash equivalents
Money market funds	$	37,284	$	—	$	—	$	37,284
Commercial paper		9,967		—		—		9,967
Total assets	$	47,251	$	—	$	—	$	47,251
June 30, 2017
Cash equivalents
Money market funds	$	38,006	$	—	$	—	$	38,006
Total assets	$	38,006	$	—	$	—	$	38,006

Schedule of Carrying and Fair Value Amounts

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 were as follows:

		June 30, 2018				December 31, 2017				June 30, 2017
(in thousands)	Fair Value Hierarchy	Carrying Value		Fair Value		Carrying Value		Fair Value		Carrying Value		Fair Value
Assets:
Held-to-maturity marketable securities	Level 1	$	81,205	$	80,006	$	132,790	$	132,002	$	107,811	$	107,381
Liabilities (including current maturities):
2019 Notes1	Level 3	$	80,000	$	81,307	$	80,000	$	82,190	$	120,000	$	123,371
Credit Agreement - term loan1	Level 3		150,000		150,608		90,000		89,871		92,500		92,046
Credit Agreement - revolving credit facility1	Level 3		99,000		99,267		55,000		55,054		30,000		29,672
Convertible notes1	Level 1		160,765		186,410		—		—		—		—

¹See Note 14 for definitions of, and more information about, the 2019 Notes, Credit Agreement and Convertible notes.