Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Allowance for doubtful accounts	$ 8,857	$ 6,212
Equity:
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	180,000	180,000
Common stock, shares issued (in shares)	84,368	88,228
Common stock, shares outstanding (in shares)	84,368	88,228
Preferred stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized (in shares)	500	500
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0