Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Financial assets and liabilities subject to fair value measurements (excluding restricted cash and cash equivalents (VIE))

The following table sets forth the Company’s financial assets and liabilities (excluding VIE cash and cash equivalents) subject to fair value measurements:

	Fair Value Measurements as of December 31, 2017
				Fair Value Hierarchy
	Total			Level 1		Level 2			Level 3
	(in thousands)
Financial instruments carried at fair value (asset position):
Cash equivalents:
Money market funds	$	614,951		$	614,951	$	—		$	—
Government-sponsored enterprise securities	12,678			12,678		—			—
Commercial paper	57,357			—		57,357			—
Marketable securities:
Corporate equity securities	74,821			74,821		—			—
Government-sponsored enterprise securities	2,303			2,303		—			—
Corporate debt securities	265,867			—		265,867			—
Commercial paper	80,263			—		80,263			—
Prepaid and other current assets:
Foreign currency forward contracts	13			—		13			—
Total financial assets	$	1,108,253		$	704,753	$	403,500		$	—
Financial instruments carried at fair value (liability position):
Other liabilities, current portion:
Foreign currency forward contracts	$	(13,642	)	$	—	$	(13,642	)	$	—
Other liabilities, excluding current portion:
Foreign currency forward contracts	(866		)	—		(866		)	—
Total financial liabilities	$	(14,508	)	$	—	$	(14,508	)	$	—

	Fair Value Measurements as of December 31, 2016
				Fair Value Hierarchy
	Total			Level 1		Level 2			Level 3
	(in thousands)
Financial instruments carried at fair value (asset position):
Cash equivalents:
Money market funds	$	280,560		$	280,560	$	—		$	—
Marketable securities:
Corporate equity securities	64,560			64,560		—			—
Government-sponsored enterprise securities	15,508			15,508		—			—
Corporate debt securities	111,140			—		111,140			—
Commercial paper	59,404			—		59,404			—
Prepaid and other current assets:
Foreign currency forward contracts	14,407			—		14,407			—
Other assets:
Foreign currency forward contracts	1,186			—		1,186			—
Total financial assets	$	546,765		$	360,628	$	186,137		$	—
Financial instruments carried at fair value (liability position):
Other liabilities, current portion:
Foreign currency forward contracts	$	(144	)	$	—	$	(144	)	$	—
Total financial liabilities	$	(144	)	$	—	$	(144	)	$	—