Balance Sheet Components - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible assets, net
Total intangible assets, net	$ 29,671	$ 43,420
Intangible asset amortization expense	$ 13,700	18,900	$ 25,800
Purchased technology
Intangible assets, net
Weighted Average Useful Life	10 years
Intangible assets	$ 104,869	104,869
Less: accumulated amortization	(76,585)	(69,768)
Total intangible assets, net	$ 28,284	35,101
Purchased technology | Minimum
Intangible assets, net
Weighted Average Useful Life	1 year
Purchased technology | Maximum
Intangible assets, net
Weighted Average Useful Life	16 years
Customer relationships
Intangible assets, net
Weighted Average Useful Life	5 years
Intangible assets	$ 75,146	75,146
Less: accumulated amortization	(73,759)	(67,311)
Total intangible assets, net	$ 1,387	7,835
Customer relationships | Minimum
Intangible assets, net
Weighted Average Useful Life	1 year
Customer relationships | Maximum
Intangible assets, net
Weighted Average Useful Life	7 years
Licenses and other
Intangible assets, net
Weighted Average Useful Life	3 years
Intangible assets	$ 7,202	7,202
Less: accumulated amortization	(7,202)	(6,718)
Total intangible assets, net	$ 0	$ 484
Licenses and other | Minimum
Intangible assets, net
Weighted Average Useful Life	2 years
Licenses and other | Maximum
Intangible assets, net
Weighted Average Useful Life	5 years