CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
CONSOLIDATED BALANCE SHEETS
Allowance for Doubtful Accounts Receivable, Current	$ 15,036	$ 14,413
Finite-Lived Intangible Assets, Accumulated Amortization	$ 269,868	$ 294,676
Common stock voting, par value (in dollars per share)	$ 0.0025	$ 0.0025
Common stock voting, shares authorized (in shares)	900,000,000	900,000,000
Common stock voting, shares issued (in shares)	265,003,133	264,130,544
Common stock voting, shares outstanding (in shares)	237,396,839	243,785,485
Treasury stock, shares (in shares)	27,606,294	20,345,059