Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenue	$ 1,511,983	$ 1,615,519	$ 2,169,461
Cost of revenue	908,404	924,618	1,323,577
Gross profit	603,579	690,901	845,884
Operating expenses:
Research and development	332,169	343,012	320,191
Sales and marketing	344,091	415,042	491,255
General and administrative	116,627	133,934	146,903
Total operating expenses	792,887	891,988	958,349
Operating loss	(189,308)	(201,087)	(112,465)
Interest income, net	7,808	3,647	3,156
Other income (expense), net	(2,642)	2,796	14
Loss before income taxes	(184,142)	(194,644)	(109,295)
Income tax expense (benefit)	1,687	82,548	(6,518)
Net loss	$ (185,829)	$ (277,192)	$ (102,777)
Net loss per share attributable to common stockholders:
Basic (in dollars per share)	$ (0.76)	$ (1.19)	$ (0.47)
Diluted (in dollars per share)	$ (0.76)	$ (1.19)	$ (0.47)
Shares used to compute net loss per share attributable to common stockholders:
Basic (in shares)	244,603	232,032	220,405
Diluted (in shares)	244,603	232,032	220,405