Equity Award Plan Activities - Equity Incentive Plan Shares Available for Grant (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2017 shares
Shares Available for Grant [Roll Forward]
Shares available for grant beginning balance (in shares)	11,754
Authorized (in shares)	2,124
Options granted (in shares)	(170)
Options canceled (in shares)	322
Options repurchased (in shares)	2
Shares traded for taxes (in shares)	17
Shares available for grant ending balance (in shares)	13,443
Restricted Stock Units (RSUs)
Shares Available for Grant [Roll Forward]
RSUs granted (in shares)	(666)
RSUs forfeited (in shares)	60