CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts receivable, allowances
Accounts receivable, allowances (in dollars)	$ 1,545	$ 2,038
Common stock
Common stock, par value (in dollars per share)	$ 0.000005	$ 0.000005
Common stock, authorized (in shares)	900,000,000	900,000,000
Common stock, issued (in shares)	0	0
Common stock, outstanding (in shares)	0	0
Preferred stock
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, authorized (in shares)	100,000,000	100,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Class A Common
Common stock
Common stock, par value (in dollars per share)	$ 0.000005	$ 0.000005
Common stock, authorized (in shares)	750,000,000	750,000,000
Common stock, issued (in shares)	78,566,507	77,588,018
Common stock, outstanding (in shares)	63,946,332	62,967,843
Treasury stock
Treasury stock (in shares)	14,620,175	14,620,175
Class B Common
Common stock
Common stock, par value (in dollars per share)	$ 0.000005	$ 0.000005
Common stock, authorized (in shares)	150,000,000	150,000,000
Common stock, issued (in shares)	80,608,685	80,957,495
Common stock, outstanding (in shares)	80,608,685	80,957,495