Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Measurements [Abstract]

Fair Value, by Balance Sheet Grouping

	Assets and Liabilities at Fair Value
	As of December 31, 2015
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash and cash equivalents	$	200,526	$	2,463	$	—	$	202,989
Short-term investments	312,888		5,475		—		318,363
Total cash and cash equivalents and investments	$	513,414	$	7,938	$	—	$	521,352
Liabilities
Accrued liabilities	$	—	$	—	$	12,453	$	12,453
Other long-term liabilities	—		—		10,362		10,362
Total liabilities	$	—	$	—	$	22,815	$	22,815

	Assets and Liabilities at Fair Value
	As of December 31, 2014
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash and cash equivalents	$	137,266	$	—	$	—	$	137,266
Short-term investments	201,521		552		—		202,073
Total cash and cash equivalents and investments	$	338,787	$	552	$	—	$	339,339
Liabilities
Other long-term liabilities	$	—	$	—	$	17,638	$	17,638
Total liabilities	$	—	$	—	$	17,638	$	17,638

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation

	Other Long-term Liabilities
	(in thousands)
Balance at December 31, 2012	$	29,920
Change in valuation of purchase consideration payable to former Symphony Icon stockholders	(2,210		)
Balance at December 31, 2013	27,710
Change in valuation of purchase consideration payable to former Symphony Icon stockholders	1,428
Payment of base payment obligation with common stock and cash	(11,500		)
Balance at December 31, 2014	17,638
Change in valuation of purchase consideration payable to former Symphony Icon stockholders	5,927
Payment of contingent payment obligation with cash	(750		)
Balance at December 31, 2015	$	22,815