Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value, Assets Measured on Recurring Basis

The following table summarizes, by major security type, the Company's cash equivalents and investments that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy (in thousands):



	Total Estimated Fair Value as of
	December 31, 2017				December 31, 2016
	Cash Equivalents		Investments		Cash Equivalents		Investments
Level 1 Securities:
Money market funds	$	151,071	$	—	$	808	$	—
Level 2 Securities:
Corporate debt securities	21,592		61,124		2,309		19,550
Agency securities	6,444		12,750		—		13,302
U.S. Government securities	—		11,843		—		6,252
Commercial Paper	85,599		101,546		6,694		1,727
Total cash equivalents and investments	$	264,706	$	187,263	$	9,811	$	40,831

Schedule of Derivative Assets at Fair Value

As of December 31, 2017, the fair value of the interest-rate swap agreements, which were determined based on an income-based valuation model that takes into account the contract terms as well as multiple observable market inputs such as LIBOR-based yield curves, futures, volatilities and basis spreads (Level 2), were as follows (the Company had no outstanding derivative financial instruments as of December 31, 2016) (in thousands):



	Total Estimated Fair Value as of
	December 31, 2017
Derivative assets	$	2,979

Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis

As of December 31, 2017, and 2016, the fair value of the Company's borrowings, which was determined based on inputs that are observable in the market or that could be derived from, or corroborated with, observable market data, including the Company's stock price, interest rates and credit spread (Level 2) were as follows (in thousands):



	Total Estimated Fair Value as of
	December 31, 2017		December 31, 2016
Convertible senior notes	$	296,550	$	290,436
Term Loan	300,000		—