Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Assets And Liabilities Measured At Fair Value

The following table presents information about the Company's assets and liabilities measured at fair value:

			Fair Value Measurements at March 31, 2018
	Total		Level 1		Level 2		Level 3
Assets
Cash equivalents	$	462,087	$	462,087	$	—	$	—
Short-term investments	206,402		206,402		—		—
Interest rate swap	18		—		18		—
Auction rate securities	1,019		—		—		1,019
Total assets	$	669,526	$	668,489	$	18	$	1,019
Liabilities
Long-term notes	$	48,087	$	—	$	48,087	$	—
Contingent purchase consideration	902		—		—		902
Total liabilities	$	48,989	$	—	$	48,087	$	902
			Fair Value Measurements at December 31, 2017
	Total		Level 1		Level 2		Level 3
Assets
Cash equivalents	$	425,917	$	425,917	$	—	$	—
Short-term investments	206,161		206,161		—		—
Interest rate swap	16		—		16		—
Auction rate securities	1,016		—		—		1,016
Total assets	$	633,110	$	632,078	$	16	$	1,016
Liabilities
Long-term notes	$	48,982	$	—	$	48,982	$	—
Contingent purchase consideration	902		—		—		902
Total liabilities	$	49,884	$	—	$	48,982	$	902

Fair Value, Assets Measured on Recurring Basis

The following table presents information about the Company's movement in Level 3 assets and liabilities measured at fair value:

	Three Months Ended March 31,
	2018		2017
Auction Rate Securities
Balance, beginning of period	$	1,016	$	1,144
Change in fair value and accretion	3		2
Balance, end of period	$	1,019	$	1,146
Contingent Purchase Consideration
Balance, beginning of period	$	902	$	—
Balance, end of period	$	902	$	—

Fair Value, Liabilities Measured on Recurring Basis

The following table presents information about the Company's movement in Level 3 assets and liabilities measured at fair value:

	Three Months Ended March 31,
	2018		2017
Auction Rate Securities
Balance, beginning of period	$	1,016	$	1,144
Change in fair value and accretion	3		2
Balance, end of period	$	1,019	$	1,146
Contingent Purchase Consideration
Balance, beginning of period	$	902	$	—
Balance, end of period	$	902	$	—