Investments - Schedule of Available-for-Sale Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Cost	$ (202,567)	$ (210,470)
Gross Unrealized Gain	(56)	(10)
Gross Unrealized Loss	(131)	(333)
Estimated Fair Value	(202,492)	(210,147)
Short-term investments | Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost	(53,663)	(52,102)
Gross Unrealized Gain	(5)	0
Gross Unrealized Loss	(55)	(129)
Estimated Fair Value	(53,613)	(51,973)
Short-term investments | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cost	(78,721)	(76,711)
Gross Unrealized Gain	(22)	(3)
Gross Unrealized Loss	0	(9)
Estimated Fair Value	(78,743)	(76,705)
Short-term investments | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cost	(77,742)	(81,777)
Gross Unrealized Gain	(18)	0
Gross Unrealized Loss	(74)	(177)
Estimated Fair Value	(77,686)	(81,600)
Short-term investments | Government agency securities
Schedule of Available-for-sale Securities [Line Items]
Cost	(17,202)	(12,701)
Gross Unrealized Gain	(4)	0
Gross Unrealized Loss	0	(17)
Estimated Fair Value	(17,206)	(12,684)
Short-term investments | Other securities
Schedule of Available-for-sale Securities [Line Items]
Cost	(11,626)	(15,122)
Gross Unrealized Gain	(9)	(7)
Gross Unrealized Loss	(2)	(1)
Estimated Fair Value	(11,633)	(15,128)
Short-term investments | Amounts classified as cash equivalents
Schedule of Available-for-sale Securities [Line Items]
Cost	(36,387)	(27,943)
Gross Unrealized Gain	(2)	0
Gross Unrealized Loss	0	0
Estimated Fair Value	(36,389)	(27,943)
Investments
Schedule of Available-for-sale Securities [Line Items]
Cost	(63,304)	(62,414)
Gross Unrealized Gain	(97)	(3)
Gross Unrealized Loss	(40)	(242)
Estimated Fair Value	(63,361)	(62,175)
Investments | Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost	(11,933)	(11,884)
Gross Unrealized Gain	(9)	0
Gross Unrealized Loss	(25)	(66)
Estimated Fair Value	(11,917)	(11,818)
Investments | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cost	(35,372)	(36,530)
Gross Unrealized Gain	(79)	(3)
Gross Unrealized Loss	(15)	(119)
Estimated Fair Value	(35,436)	(36,414)
Investments | Government agency securities
Schedule of Available-for-sale Securities [Line Items]
Cost	(11,999)	(11,999)
Gross Unrealized Gain	(1)	0
Gross Unrealized Loss	0	(55)
Estimated Fair Value	(12,000)	(11,944)
Investments | Other securities
Schedule of Available-for-sale Securities [Line Items]
Cost	(4,000)	(2,001)
Gross Unrealized Gain	(8)	0
Gross Unrealized Loss	0	(2)
Estimated Fair Value	$ (4,008)	$ (1,999)