Investments - Schedule of Available-for-Sale Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 223,068	$ 210,470
Gross Unrealized Gain	141	10
Gross Unrealized Loss	54	333
Estimated Fair Value	223,155	210,147
Short-term investments | Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost	51,338	52,102
Gross Unrealized Gain	43	0
Gross Unrealized Loss	34	129
Estimated Fair Value	51,347	51,973
Short-term investments | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cost	75,678	76,711
Gross Unrealized Gain	21	3
Gross Unrealized Loss	0	9
Estimated Fair Value	75,699	76,705
Short-term investments | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cost	80,827	81,777
Gross Unrealized Gain	27	0
Gross Unrealized Loss	20	177
Estimated Fair Value	80,834	81,600
Short-term investments | Government agency securities
Schedule of Available-for-sale Securities [Line Items]
Cost	31,208	12,701
Gross Unrealized Gain	50	0
Gross Unrealized Loss	1	17
Estimated Fair Value	31,257	12,684
Short-term investments | Other securities
Schedule of Available-for-sale Securities [Line Items]
Cost	8,711	15,122
Gross Unrealized Gain	1	7
Gross Unrealized Loss	0	1
Estimated Fair Value	8,712	15,128
Short-term investments | Amounts classified as cash equivalents
Schedule of Available-for-sale Securities [Line Items]
Cost	24,694	27,943
Gross Unrealized Gain	1	0
Gross Unrealized Loss	1	0
Estimated Fair Value	24,694	27,943
Investments
Schedule of Available-for-sale Securities [Line Items]
Cost	55,023	62,414
Gross Unrealized Gain	169	3
Gross Unrealized Loss	8	242
Estimated Fair Value	55,184	62,175
Investments | Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost	17,199	11,884
Gross Unrealized Gain	28	0
Gross Unrealized Loss	0	66
Estimated Fair Value	17,227	11,818
Investments | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cost	33,824	36,530
Gross Unrealized Gain	123	3
Gross Unrealized Loss	8	119
Estimated Fair Value	33,939	36,414
Investments | Government agency securities
Schedule of Available-for-sale Securities [Line Items]
Cost	0	11,999
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	55
Estimated Fair Value	0	11,944
Investments | Other securities
Schedule of Available-for-sale Securities [Line Items]
Cost	4,000	2,001
Gross Unrealized Gain	18	0
Gross Unrealized Loss	0	2
Estimated Fair Value	$ 4,018	$ 1,999